Related
I've built a simple music player in Android. The view for each song contains a SeekBar, implemented like this:
public class Song extends Activity implements OnClickListener,Runnable {
private SeekBar progress;
private MediaPlayer mp;
// ...
private ServiceConnection onService = new ServiceConnection() {
public void onServiceConnected(ComponentName className,
IBinder rawBinder) {
appService = ((MPService.LocalBinder)rawBinder).getService(); // service that handles the MediaPlayer
progress.setVisibility(SeekBar.VISIBLE);
progress.setProgress(0);
mp = appService.getMP();
appService.playSong(title);
progress.setMax(mp.getDuration());
new Thread(Song.this).start();
}
public void onServiceDisconnected(ComponentName classname) {
appService = null;
}
};
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.song);
// ...
progress = (SeekBar) findViewById(R.id.progress);
// ...
}
public void run() {
int pos = 0;
int total = mp.getDuration();
while (mp != null && pos<total) {
try {
Thread.sleep(1000);
pos = appService.getSongPosition();
} catch (InterruptedException e) {
return;
} catch (Exception e) {
return;
}
progress.setProgress(pos);
}
}
This works fine. Now I want a timer counting the seconds/minutes of the progress of the song. So I put a TextView in the layout, get it with findViewById() in onCreate(), and put this in run() after progress.setProgress(pos):
String time = String.format("%d:%d",
TimeUnit.MILLISECONDS.toMinutes(pos),
TimeUnit.MILLISECONDS.toSeconds(pos),
TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(
pos))
);
currentTime.setText(time); // currentTime = (TextView) findViewById(R.id.current_time);
But that last line gives me the exception:
android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
Yet I'm doing basically the same thing here as I'm doing with the SeekBar - creating the view in onCreate, then touching it in run() - and it doesn't give me this complaint.
You have to move the portion of the background task that updates the UI onto the main thread. There is a simple piece of code for this:
runOnUiThread(new Runnable() {
#Override
public void run() {
// Stuff that updates the UI
}
});
Documentation for Activity.runOnUiThread.
Just nest this inside the method that is running in the background, and then copy paste the code that implements any updates in the middle of the block. Include only the smallest amount of code possible, otherwise you start to defeat the purpose of the background thread.
I solved this by putting runOnUiThread( new Runnable(){ .. inside run():
thread = new Thread(){
#Override
public void run() {
try {
synchronized (this) {
wait(5000);
runOnUiThread(new Runnable() {
#Override
public void run() {
dbloadingInfo.setVisibility(View.VISIBLE);
bar.setVisibility(View.INVISIBLE);
loadingText.setVisibility(View.INVISIBLE);
}
});
}
} catch (InterruptedException e) {
e.printStackTrace();
}
Intent mainActivity = new Intent(getApplicationContext(),MainActivity.class);
startActivity(mainActivity);
};
};
thread.start();
My solution to this:
private void setText(final TextView text,final String value){
runOnUiThread(new Runnable() {
#Override
public void run() {
text.setText(value);
}
});
}
Call this method on a background thread.
Kotlin coroutines can make your code more concise and readable like this:
MainScope().launch {
withContext(Dispatchers.Default) {
//TODO("Background processing...")
}
TODO("Update UI here!")
}
Or vice versa:
GlobalScope.launch {
//TODO("Background processing...")
withContext(Dispatchers.Main) {
// TODO("Update UI here!")
}
TODO("Continue background processing...")
}
Usually, any action involving the user interface must be done in the main or UI thread, that is the one in which onCreate() and event handling are executed. One way to be sure of that is using runOnUiThread(), another is using Handlers.
ProgressBar.setProgress() has a mechanism for which it will always execute on the main thread, so that's why it worked.
See Painless Threading.
You can use Handler to Delete View without disturbing the main UI Thread.
Here is example code
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
//do stuff like remove view etc
adapter.remove(selecteditem);
}
});
Kotlin Answer
We have to use UI Thread for the job with true way. We can use UI Thread in Kotlin, such as:
runOnUiThread(Runnable {
//TODO: Your job is here..!
})
I've been in this situation, but I found a solution with the Handler Object.
In my case, I want to update a ProgressDialog with the observer pattern.
My view implements observer and overrides the update method.
So, my main thread create the view and another thread call the update method that update the ProgressDialop and....:
Only the original thread that created a view hierarchy can touch its
views.
It's possible to solve the problem with the Handler Object.
Below, different parts of my code:
public class ViewExecution extends Activity implements Observer{
static final int PROGRESS_DIALOG = 0;
ProgressDialog progressDialog;
int currentNumber;
public void onCreate(Bundle savedInstanceState) {
currentNumber = 0;
final Button launchPolicyButton = ((Button) this.findViewById(R.id.launchButton));
launchPolicyButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
showDialog(PROGRESS_DIALOG);
}
});
}
#Override
protected Dialog onCreateDialog(int id) {
switch(id) {
case PROGRESS_DIALOG:
progressDialog = new ProgressDialog(this);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Loading");
progressDialog.setCancelable(true);
return progressDialog;
default:
return null;
}
}
#Override
protected void onPrepareDialog(int id, Dialog dialog) {
switch(id) {
case PROGRESS_DIALOG:
progressDialog.setProgress(0);
}
}
// Define the Handler that receives messages from the thread and update the progress
final Handler handler = new Handler() {
public void handleMessage(Message msg) {
int current = msg.arg1;
progressDialog.setProgress(current);
if (current >= 100){
removeDialog (PROGRESS_DIALOG);
}
}
};
// The method called by the observer (the second thread)
#Override
public void update(Observable obs, Object arg1) {
Message msg = handler.obtainMessage();
msg.arg1 = ++currentPluginNumber;
handler.sendMessage(msg);
}
}
This explanation can be found on this page, and you must read the "Example ProgressDialog with a second thread".
I see that you have accepted #providence's answer. Just in case, you can also use the handler too! First, do the int fields.
private static final int SHOW_LOG = 1;
private static final int HIDE_LOG = 0;
Next, make a handler instance as a field.
//TODO __________[ Handler ]__________
#SuppressLint("HandlerLeak")
protected Handler handler = new Handler()
{
#Override
public void handleMessage(Message msg)
{
// Put code here...
// Set a switch statement to toggle it on or off.
switch(msg.what)
{
case SHOW_LOG:
{
ads.setVisibility(View.VISIBLE);
break;
}
case HIDE_LOG:
{
ads.setVisibility(View.GONE);
break;
}
}
}
};
Make a method.
//TODO __________[ Callbacks ]__________
#Override
public void showHandler(boolean show)
{
handler.sendEmptyMessage(show ? SHOW_LOG : HIDE_LOG);
}
Finally, put this at onCreate() method.
showHandler(true);
Use this code, and no need to runOnUiThread function:
private Handler handler;
private Runnable handlerTask;
void StartTimer(){
handler = new Handler();
handlerTask = new Runnable()
{
#Override
public void run() {
// do something
textView.setText("some text");
handler.postDelayed(handlerTask, 1000);
}
};
handlerTask.run();
}
I had a similar issue, and my solution is ugly, but it works:
void showCode() {
hideRegisterMessage(); // Hides view
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
showRegisterMessage(); // Shows view
}
}, 3000); // After 3 seconds
}
I was facing a similar problem and none of the methods mentioned above worked for me. In the end, this did the trick for me:
Device.BeginInvokeOnMainThread(() =>
{
myMethod();
});
I found this gem here.
I use Handler with Looper.getMainLooper(). It worked fine for me.
Handler handler = new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(Message msg) {
// Any UI task, example
textView.setText("your text");
}
};
handler.sendEmptyMessage(1);
This is explicitly throwing an error. It says whichever thread created a view, only that can touch its views. It is because the created view is inside that thread's space. The view creation (GUI) happens in the UI (main) thread. So, you always use the UI thread to access those methods.
In the above picture, the progress variable is inside the space of the UI thread. So, only the UI thread can access this variable. Here, you're accessing progress via new Thread(), and that's why you got an error.
For a one-liner version of the runOnUiThread() approach, you can use a lambda function, i.e.:
runOnUiThread(() -> doStuff(Object, myValue));
where doStuff() can represents some method used to modify the value of some UI Object (setting text, changing colors, etc.).
I find this to be much neater when trying to update several UI objects without the need for a 6 line Runnable definition at each as mentioned in the most upvoted answer, which is by no means incorrect, it just takes up a lot more space and I find to be less readable.
So this:
runOnUiThread(new Runnable() {
#Override
public void run() {
doStuff(myTextView, "myNewText");
}
});
can become this:
runOnUiThread(() -> doStuff(myTextView, "myNewText"));
where the definition of doStuff lies elsewhere.
Or if you don't need to be so generalizable, and just need to set the text of a TextView object:
runOnUiThread(() -> myTextView.setText("myNewText"));
For anyone using fragment:
(context as Activity).runOnUiThread {
//TODO
}
This happened to my when I called for an UI change from a doInBackground from Asynctask instead of using onPostExecute.
Dealing with the UI in onPostExecute solved my problem.
I was working with a class that did not contain a reference to the context. So it was not possible for me to use runOnUIThread(); I used view.post(); and it was solved.
timer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
final int currentPosition = mediaPlayer.getCurrentPosition();
audioMessage.seekBar.setProgress(currentPosition / 1000);
audioMessage.tvPlayDuration.post(new Runnable() {
#Override
public void run() {
audioMessage.tvPlayDuration.setText(ChatDateTimeFormatter.getDuration(currentPosition));
}
});
}
}, 0, 1000);
When using AsyncTask Update the UI in onPostExecute method
#Override
protected void onPostExecute(String s) {
// Update UI here
}
This is the stack trace of mentioned exception
at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6149)
at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:843)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:352)
at android.view.View.requestLayout(View.java:16474)
at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:352)
at android.view.View.setFlags(View.java:8938)
at android.view.View.setVisibility(View.java:6066)
So if you go and dig then you come to know
void checkThread() {
if (mThread != Thread.currentThread()) {
throw new CalledFromWrongThreadException(
"Only the original thread that created a view hierarchy can touch its views.");
}
}
Where mThread is initialize in constructor like below
mThread = Thread.currentThread();
All I mean to say that when we created particular view we created it on UI Thread and later try to modifying in a Worker Thread.
We can verify it via below code snippet
Thread.currentThread().getName()
when we inflate layout and later where you are getting exception.
If you do not want to use runOnUiThread API, you can in fact implement AsynTask for the operations that takes some seconds to complete. But in that case, also after processing your work in doinBackground(), you need to return the finished view in onPostExecute(). The Android implementation allows only main UI thread to interact with views.
If you simply want to invalidate (call repaint/redraw function) from your non UI Thread, use postInvalidate()
myView.postInvalidate();
This will post an invalidate request on the UI-thread.
For more information : what-does-postinvalidate-do
Well, You can do it like this.
https://developer.android.com/reference/android/view/View#post(java.lang.Runnable)
A simple approach
currentTime.post(new Runnable(){
#Override
public void run() {
currentTime.setText(time);
}
}
it also provides delay
https://developer.android.com/reference/android/view/View#postDelayed(java.lang.Runnable,%20long)
For me the issue was that I was calling onProgressUpdate() explicitly from my code. This shouldn't be done. I called publishProgress() instead and that resolved the error.
In my case,
I have EditText in Adaptor, and it's already in the UI thread. However, when this Activity loads, it's crashes with this error.
My solution is I need to remove <requestFocus /> out from EditText in XML.
For the people struggling in Kotlin, it works like this:
lateinit var runnable: Runnable //global variable
runOnUiThread { //Lambda
runnable = Runnable {
//do something here
runDelayedHandler(5000)
}
}
runnable.run()
//you need to keep the handler outside the runnable body to work in kotlin
fun runDelayedHandler(timeToWait: Long) {
//Keep it running
val handler = Handler()
handler.postDelayed(runnable, timeToWait)
}
If you couldn't find a UIThread you can use this way .
yourcurrentcontext mean, you need to parse Current Context
new Thread(new Runnable() {
public void run() {
while (true) {
(Activity) yourcurrentcontext).runOnUiThread(new Runnable() {
public void run() {
Log.d("Thread Log","I am from UI Thread");
}
});
try {
Thread.sleep(1000);
} catch (Exception ex) {
}
}
}
}).start();
In Kotlin simply put your code in runOnUiThread activity method
runOnUiThread{
// write your code here, for example
val task = Runnable {
Handler().postDelayed({
var smzHtcList = mDb?.smzHtcReferralDao()?.getAll()
tv_showSmzHtcList.text = smzHtcList.toString()
}, 10)
}
mDbWorkerThread.postTask(task)
}
If you are within a fragment, then you also need to get the activity object as runOnUIThread is a method on the activity.
An example in Kotlin with some surrounding context to make it clearer - this example is navigating from a camera fragment to a gallery fragment:
// Setup image capture listener which is triggered after photo has been taken
imageCapture.takePicture(
outputOptions, cameraExecutor, object : ImageCapture.OnImageSavedCallback {
override fun onError(exc: ImageCaptureException) {
Log.e(TAG, "Photo capture failed: ${exc.message}", exc)
}
override fun onImageSaved(output: ImageCapture.OutputFileResults) {
val savedUri = output.savedUri ?: Uri.fromFile(photoFile)
Log.d(TAG, "Photo capture succeeded: $savedUri")
//Do whatever work you do when image is saved
//Now ask navigator to move to new tab - as this
//updates UI do on the UI thread
activity?.runOnUiThread( {
Navigation.findNavController(
requireActivity(), R.id.fragment_container
).navigate(CameraFragmentDirections
.actionCameraToGallery(outputDirectory.absolutePath))
})
Solved : Just put this method in doInBackround Class... and pass the message
public void setProgressText(final String progressText){
Handler handler = new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(Message msg) {
// Any UI task, example
progressDialog.setMessage(progressText);
}
};
handler.sendEmptyMessage(1);
}
I've built a simple music player in Android. The view for each song contains a SeekBar, implemented like this:
public class Song extends Activity implements OnClickListener,Runnable {
private SeekBar progress;
private MediaPlayer mp;
// ...
private ServiceConnection onService = new ServiceConnection() {
public void onServiceConnected(ComponentName className,
IBinder rawBinder) {
appService = ((MPService.LocalBinder)rawBinder).getService(); // service that handles the MediaPlayer
progress.setVisibility(SeekBar.VISIBLE);
progress.setProgress(0);
mp = appService.getMP();
appService.playSong(title);
progress.setMax(mp.getDuration());
new Thread(Song.this).start();
}
public void onServiceDisconnected(ComponentName classname) {
appService = null;
}
};
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.song);
// ...
progress = (SeekBar) findViewById(R.id.progress);
// ...
}
public void run() {
int pos = 0;
int total = mp.getDuration();
while (mp != null && pos<total) {
try {
Thread.sleep(1000);
pos = appService.getSongPosition();
} catch (InterruptedException e) {
return;
} catch (Exception e) {
return;
}
progress.setProgress(pos);
}
}
This works fine. Now I want a timer counting the seconds/minutes of the progress of the song. So I put a TextView in the layout, get it with findViewById() in onCreate(), and put this in run() after progress.setProgress(pos):
String time = String.format("%d:%d",
TimeUnit.MILLISECONDS.toMinutes(pos),
TimeUnit.MILLISECONDS.toSeconds(pos),
TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(
pos))
);
currentTime.setText(time); // currentTime = (TextView) findViewById(R.id.current_time);
But that last line gives me the exception:
android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
Yet I'm doing basically the same thing here as I'm doing with the SeekBar - creating the view in onCreate, then touching it in run() - and it doesn't give me this complaint.
You have to move the portion of the background task that updates the UI onto the main thread. There is a simple piece of code for this:
runOnUiThread(new Runnable() {
#Override
public void run() {
// Stuff that updates the UI
}
});
Documentation for Activity.runOnUiThread.
Just nest this inside the method that is running in the background, and then copy paste the code that implements any updates in the middle of the block. Include only the smallest amount of code possible, otherwise you start to defeat the purpose of the background thread.
I solved this by putting runOnUiThread( new Runnable(){ .. inside run():
thread = new Thread(){
#Override
public void run() {
try {
synchronized (this) {
wait(5000);
runOnUiThread(new Runnable() {
#Override
public void run() {
dbloadingInfo.setVisibility(View.VISIBLE);
bar.setVisibility(View.INVISIBLE);
loadingText.setVisibility(View.INVISIBLE);
}
});
}
} catch (InterruptedException e) {
e.printStackTrace();
}
Intent mainActivity = new Intent(getApplicationContext(),MainActivity.class);
startActivity(mainActivity);
};
};
thread.start();
My solution to this:
private void setText(final TextView text,final String value){
runOnUiThread(new Runnable() {
#Override
public void run() {
text.setText(value);
}
});
}
Call this method on a background thread.
Kotlin coroutines can make your code more concise and readable like this:
MainScope().launch {
withContext(Dispatchers.Default) {
//TODO("Background processing...")
}
TODO("Update UI here!")
}
Or vice versa:
GlobalScope.launch {
//TODO("Background processing...")
withContext(Dispatchers.Main) {
// TODO("Update UI here!")
}
TODO("Continue background processing...")
}
Usually, any action involving the user interface must be done in the main or UI thread, that is the one in which onCreate() and event handling are executed. One way to be sure of that is using runOnUiThread(), another is using Handlers.
ProgressBar.setProgress() has a mechanism for which it will always execute on the main thread, so that's why it worked.
See Painless Threading.
You can use Handler to Delete View without disturbing the main UI Thread.
Here is example code
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
//do stuff like remove view etc
adapter.remove(selecteditem);
}
});
Kotlin Answer
We have to use UI Thread for the job with true way. We can use UI Thread in Kotlin, such as:
runOnUiThread(Runnable {
//TODO: Your job is here..!
})
I've been in this situation, but I found a solution with the Handler Object.
In my case, I want to update a ProgressDialog with the observer pattern.
My view implements observer and overrides the update method.
So, my main thread create the view and another thread call the update method that update the ProgressDialop and....:
Only the original thread that created a view hierarchy can touch its
views.
It's possible to solve the problem with the Handler Object.
Below, different parts of my code:
public class ViewExecution extends Activity implements Observer{
static final int PROGRESS_DIALOG = 0;
ProgressDialog progressDialog;
int currentNumber;
public void onCreate(Bundle savedInstanceState) {
currentNumber = 0;
final Button launchPolicyButton = ((Button) this.findViewById(R.id.launchButton));
launchPolicyButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
showDialog(PROGRESS_DIALOG);
}
});
}
#Override
protected Dialog onCreateDialog(int id) {
switch(id) {
case PROGRESS_DIALOG:
progressDialog = new ProgressDialog(this);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Loading");
progressDialog.setCancelable(true);
return progressDialog;
default:
return null;
}
}
#Override
protected void onPrepareDialog(int id, Dialog dialog) {
switch(id) {
case PROGRESS_DIALOG:
progressDialog.setProgress(0);
}
}
// Define the Handler that receives messages from the thread and update the progress
final Handler handler = new Handler() {
public void handleMessage(Message msg) {
int current = msg.arg1;
progressDialog.setProgress(current);
if (current >= 100){
removeDialog (PROGRESS_DIALOG);
}
}
};
// The method called by the observer (the second thread)
#Override
public void update(Observable obs, Object arg1) {
Message msg = handler.obtainMessage();
msg.arg1 = ++currentPluginNumber;
handler.sendMessage(msg);
}
}
This explanation can be found on this page, and you must read the "Example ProgressDialog with a second thread".
I see that you have accepted #providence's answer. Just in case, you can also use the handler too! First, do the int fields.
private static final int SHOW_LOG = 1;
private static final int HIDE_LOG = 0;
Next, make a handler instance as a field.
//TODO __________[ Handler ]__________
#SuppressLint("HandlerLeak")
protected Handler handler = new Handler()
{
#Override
public void handleMessage(Message msg)
{
// Put code here...
// Set a switch statement to toggle it on or off.
switch(msg.what)
{
case SHOW_LOG:
{
ads.setVisibility(View.VISIBLE);
break;
}
case HIDE_LOG:
{
ads.setVisibility(View.GONE);
break;
}
}
}
};
Make a method.
//TODO __________[ Callbacks ]__________
#Override
public void showHandler(boolean show)
{
handler.sendEmptyMessage(show ? SHOW_LOG : HIDE_LOG);
}
Finally, put this at onCreate() method.
showHandler(true);
Use this code, and no need to runOnUiThread function:
private Handler handler;
private Runnable handlerTask;
void StartTimer(){
handler = new Handler();
handlerTask = new Runnable()
{
#Override
public void run() {
// do something
textView.setText("some text");
handler.postDelayed(handlerTask, 1000);
}
};
handlerTask.run();
}
I had a similar issue, and my solution is ugly, but it works:
void showCode() {
hideRegisterMessage(); // Hides view
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
showRegisterMessage(); // Shows view
}
}, 3000); // After 3 seconds
}
I was facing a similar problem and none of the methods mentioned above worked for me. In the end, this did the trick for me:
Device.BeginInvokeOnMainThread(() =>
{
myMethod();
});
I found this gem here.
I use Handler with Looper.getMainLooper(). It worked fine for me.
Handler handler = new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(Message msg) {
// Any UI task, example
textView.setText("your text");
}
};
handler.sendEmptyMessage(1);
This is explicitly throwing an error. It says whichever thread created a view, only that can touch its views. It is because the created view is inside that thread's space. The view creation (GUI) happens in the UI (main) thread. So, you always use the UI thread to access those methods.
In the above picture, the progress variable is inside the space of the UI thread. So, only the UI thread can access this variable. Here, you're accessing progress via new Thread(), and that's why you got an error.
For a one-liner version of the runOnUiThread() approach, you can use a lambda function, i.e.:
runOnUiThread(() -> doStuff(Object, myValue));
where doStuff() can represents some method used to modify the value of some UI Object (setting text, changing colors, etc.).
I find this to be much neater when trying to update several UI objects without the need for a 6 line Runnable definition at each as mentioned in the most upvoted answer, which is by no means incorrect, it just takes up a lot more space and I find to be less readable.
So this:
runOnUiThread(new Runnable() {
#Override
public void run() {
doStuff(myTextView, "myNewText");
}
});
can become this:
runOnUiThread(() -> doStuff(myTextView, "myNewText"));
where the definition of doStuff lies elsewhere.
Or if you don't need to be so generalizable, and just need to set the text of a TextView object:
runOnUiThread(() -> myTextView.setText("myNewText"));
For anyone using fragment:
(context as Activity).runOnUiThread {
//TODO
}
This happened to my when I called for an UI change from a doInBackground from Asynctask instead of using onPostExecute.
Dealing with the UI in onPostExecute solved my problem.
I was working with a class that did not contain a reference to the context. So it was not possible for me to use runOnUIThread(); I used view.post(); and it was solved.
timer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
final int currentPosition = mediaPlayer.getCurrentPosition();
audioMessage.seekBar.setProgress(currentPosition / 1000);
audioMessage.tvPlayDuration.post(new Runnable() {
#Override
public void run() {
audioMessage.tvPlayDuration.setText(ChatDateTimeFormatter.getDuration(currentPosition));
}
});
}
}, 0, 1000);
When using AsyncTask Update the UI in onPostExecute method
#Override
protected void onPostExecute(String s) {
// Update UI here
}
This is the stack trace of mentioned exception
at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6149)
at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:843)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:352)
at android.view.View.requestLayout(View.java:16474)
at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:352)
at android.view.View.setFlags(View.java:8938)
at android.view.View.setVisibility(View.java:6066)
So if you go and dig then you come to know
void checkThread() {
if (mThread != Thread.currentThread()) {
throw new CalledFromWrongThreadException(
"Only the original thread that created a view hierarchy can touch its views.");
}
}
Where mThread is initialize in constructor like below
mThread = Thread.currentThread();
All I mean to say that when we created particular view we created it on UI Thread and later try to modifying in a Worker Thread.
We can verify it via below code snippet
Thread.currentThread().getName()
when we inflate layout and later where you are getting exception.
If you do not want to use runOnUiThread API, you can in fact implement AsynTask for the operations that takes some seconds to complete. But in that case, also after processing your work in doinBackground(), you need to return the finished view in onPostExecute(). The Android implementation allows only main UI thread to interact with views.
If you simply want to invalidate (call repaint/redraw function) from your non UI Thread, use postInvalidate()
myView.postInvalidate();
This will post an invalidate request on the UI-thread.
For more information : what-does-postinvalidate-do
Well, You can do it like this.
https://developer.android.com/reference/android/view/View#post(java.lang.Runnable)
A simple approach
currentTime.post(new Runnable(){
#Override
public void run() {
currentTime.setText(time);
}
}
it also provides delay
https://developer.android.com/reference/android/view/View#postDelayed(java.lang.Runnable,%20long)
For me the issue was that I was calling onProgressUpdate() explicitly from my code. This shouldn't be done. I called publishProgress() instead and that resolved the error.
In my case,
I have EditText in Adaptor, and it's already in the UI thread. However, when this Activity loads, it's crashes with this error.
My solution is I need to remove <requestFocus /> out from EditText in XML.
For the people struggling in Kotlin, it works like this:
lateinit var runnable: Runnable //global variable
runOnUiThread { //Lambda
runnable = Runnable {
//do something here
runDelayedHandler(5000)
}
}
runnable.run()
//you need to keep the handler outside the runnable body to work in kotlin
fun runDelayedHandler(timeToWait: Long) {
//Keep it running
val handler = Handler()
handler.postDelayed(runnable, timeToWait)
}
If you couldn't find a UIThread you can use this way .
yourcurrentcontext mean, you need to parse Current Context
new Thread(new Runnable() {
public void run() {
while (true) {
(Activity) yourcurrentcontext).runOnUiThread(new Runnable() {
public void run() {
Log.d("Thread Log","I am from UI Thread");
}
});
try {
Thread.sleep(1000);
} catch (Exception ex) {
}
}
}
}).start();
In Kotlin simply put your code in runOnUiThread activity method
runOnUiThread{
// write your code here, for example
val task = Runnable {
Handler().postDelayed({
var smzHtcList = mDb?.smzHtcReferralDao()?.getAll()
tv_showSmzHtcList.text = smzHtcList.toString()
}, 10)
}
mDbWorkerThread.postTask(task)
}
If you are within a fragment, then you also need to get the activity object as runOnUIThread is a method on the activity.
An example in Kotlin with some surrounding context to make it clearer - this example is navigating from a camera fragment to a gallery fragment:
// Setup image capture listener which is triggered after photo has been taken
imageCapture.takePicture(
outputOptions, cameraExecutor, object : ImageCapture.OnImageSavedCallback {
override fun onError(exc: ImageCaptureException) {
Log.e(TAG, "Photo capture failed: ${exc.message}", exc)
}
override fun onImageSaved(output: ImageCapture.OutputFileResults) {
val savedUri = output.savedUri ?: Uri.fromFile(photoFile)
Log.d(TAG, "Photo capture succeeded: $savedUri")
//Do whatever work you do when image is saved
//Now ask navigator to move to new tab - as this
//updates UI do on the UI thread
activity?.runOnUiThread( {
Navigation.findNavController(
requireActivity(), R.id.fragment_container
).navigate(CameraFragmentDirections
.actionCameraToGallery(outputDirectory.absolutePath))
})
Solved : Just put this method in doInBackround Class... and pass the message
public void setProgressText(final String progressText){
Handler handler = new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(Message msg) {
// Any UI task, example
progressDialog.setMessage(progressText);
}
};
handler.sendEmptyMessage(1);
}
I've built a simple music player in Android. The view for each song contains a SeekBar, implemented like this:
public class Song extends Activity implements OnClickListener,Runnable {
private SeekBar progress;
private MediaPlayer mp;
// ...
private ServiceConnection onService = new ServiceConnection() {
public void onServiceConnected(ComponentName className,
IBinder rawBinder) {
appService = ((MPService.LocalBinder)rawBinder).getService(); // service that handles the MediaPlayer
progress.setVisibility(SeekBar.VISIBLE);
progress.setProgress(0);
mp = appService.getMP();
appService.playSong(title);
progress.setMax(mp.getDuration());
new Thread(Song.this).start();
}
public void onServiceDisconnected(ComponentName classname) {
appService = null;
}
};
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.song);
// ...
progress = (SeekBar) findViewById(R.id.progress);
// ...
}
public void run() {
int pos = 0;
int total = mp.getDuration();
while (mp != null && pos<total) {
try {
Thread.sleep(1000);
pos = appService.getSongPosition();
} catch (InterruptedException e) {
return;
} catch (Exception e) {
return;
}
progress.setProgress(pos);
}
}
This works fine. Now I want a timer counting the seconds/minutes of the progress of the song. So I put a TextView in the layout, get it with findViewById() in onCreate(), and put this in run() after progress.setProgress(pos):
String time = String.format("%d:%d",
TimeUnit.MILLISECONDS.toMinutes(pos),
TimeUnit.MILLISECONDS.toSeconds(pos),
TimeUnit.MINUTES.toSeconds(TimeUnit.MILLISECONDS.toMinutes(
pos))
);
currentTime.setText(time); // currentTime = (TextView) findViewById(R.id.current_time);
But that last line gives me the exception:
android.view.ViewRoot$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
Yet I'm doing basically the same thing here as I'm doing with the SeekBar - creating the view in onCreate, then touching it in run() - and it doesn't give me this complaint.
You have to move the portion of the background task that updates the UI onto the main thread. There is a simple piece of code for this:
runOnUiThread(new Runnable() {
#Override
public void run() {
// Stuff that updates the UI
}
});
Documentation for Activity.runOnUiThread.
Just nest this inside the method that is running in the background, and then copy paste the code that implements any updates in the middle of the block. Include only the smallest amount of code possible, otherwise you start to defeat the purpose of the background thread.
I solved this by putting runOnUiThread( new Runnable(){ .. inside run():
thread = new Thread(){
#Override
public void run() {
try {
synchronized (this) {
wait(5000);
runOnUiThread(new Runnable() {
#Override
public void run() {
dbloadingInfo.setVisibility(View.VISIBLE);
bar.setVisibility(View.INVISIBLE);
loadingText.setVisibility(View.INVISIBLE);
}
});
}
} catch (InterruptedException e) {
e.printStackTrace();
}
Intent mainActivity = new Intent(getApplicationContext(),MainActivity.class);
startActivity(mainActivity);
};
};
thread.start();
My solution to this:
private void setText(final TextView text,final String value){
runOnUiThread(new Runnable() {
#Override
public void run() {
text.setText(value);
}
});
}
Call this method on a background thread.
Kotlin coroutines can make your code more concise and readable like this:
MainScope().launch {
withContext(Dispatchers.Default) {
//TODO("Background processing...")
}
TODO("Update UI here!")
}
Or vice versa:
GlobalScope.launch {
//TODO("Background processing...")
withContext(Dispatchers.Main) {
// TODO("Update UI here!")
}
TODO("Continue background processing...")
}
Usually, any action involving the user interface must be done in the main or UI thread, that is the one in which onCreate() and event handling are executed. One way to be sure of that is using runOnUiThread(), another is using Handlers.
ProgressBar.setProgress() has a mechanism for which it will always execute on the main thread, so that's why it worked.
See Painless Threading.
You can use Handler to Delete View without disturbing the main UI Thread.
Here is example code
new Handler(Looper.getMainLooper()).post(new Runnable() {
#Override
public void run() {
//do stuff like remove view etc
adapter.remove(selecteditem);
}
});
Kotlin Answer
We have to use UI Thread for the job with true way. We can use UI Thread in Kotlin, such as:
runOnUiThread(Runnable {
//TODO: Your job is here..!
})
I've been in this situation, but I found a solution with the Handler Object.
In my case, I want to update a ProgressDialog with the observer pattern.
My view implements observer and overrides the update method.
So, my main thread create the view and another thread call the update method that update the ProgressDialop and....:
Only the original thread that created a view hierarchy can touch its
views.
It's possible to solve the problem with the Handler Object.
Below, different parts of my code:
public class ViewExecution extends Activity implements Observer{
static final int PROGRESS_DIALOG = 0;
ProgressDialog progressDialog;
int currentNumber;
public void onCreate(Bundle savedInstanceState) {
currentNumber = 0;
final Button launchPolicyButton = ((Button) this.findViewById(R.id.launchButton));
launchPolicyButton.setOnClickListener(new OnClickListener() {
#Override
public void onClick(View v) {
showDialog(PROGRESS_DIALOG);
}
});
}
#Override
protected Dialog onCreateDialog(int id) {
switch(id) {
case PROGRESS_DIALOG:
progressDialog = new ProgressDialog(this);
progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
progressDialog.setMessage("Loading");
progressDialog.setCancelable(true);
return progressDialog;
default:
return null;
}
}
#Override
protected void onPrepareDialog(int id, Dialog dialog) {
switch(id) {
case PROGRESS_DIALOG:
progressDialog.setProgress(0);
}
}
// Define the Handler that receives messages from the thread and update the progress
final Handler handler = new Handler() {
public void handleMessage(Message msg) {
int current = msg.arg1;
progressDialog.setProgress(current);
if (current >= 100){
removeDialog (PROGRESS_DIALOG);
}
}
};
// The method called by the observer (the second thread)
#Override
public void update(Observable obs, Object arg1) {
Message msg = handler.obtainMessage();
msg.arg1 = ++currentPluginNumber;
handler.sendMessage(msg);
}
}
This explanation can be found on this page, and you must read the "Example ProgressDialog with a second thread".
I see that you have accepted #providence's answer. Just in case, you can also use the handler too! First, do the int fields.
private static final int SHOW_LOG = 1;
private static final int HIDE_LOG = 0;
Next, make a handler instance as a field.
//TODO __________[ Handler ]__________
#SuppressLint("HandlerLeak")
protected Handler handler = new Handler()
{
#Override
public void handleMessage(Message msg)
{
// Put code here...
// Set a switch statement to toggle it on or off.
switch(msg.what)
{
case SHOW_LOG:
{
ads.setVisibility(View.VISIBLE);
break;
}
case HIDE_LOG:
{
ads.setVisibility(View.GONE);
break;
}
}
}
};
Make a method.
//TODO __________[ Callbacks ]__________
#Override
public void showHandler(boolean show)
{
handler.sendEmptyMessage(show ? SHOW_LOG : HIDE_LOG);
}
Finally, put this at onCreate() method.
showHandler(true);
Use this code, and no need to runOnUiThread function:
private Handler handler;
private Runnable handlerTask;
void StartTimer(){
handler = new Handler();
handlerTask = new Runnable()
{
#Override
public void run() {
// do something
textView.setText("some text");
handler.postDelayed(handlerTask, 1000);
}
};
handlerTask.run();
}
I had a similar issue, and my solution is ugly, but it works:
void showCode() {
hideRegisterMessage(); // Hides view
final Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run() {
showRegisterMessage(); // Shows view
}
}, 3000); // After 3 seconds
}
I was facing a similar problem and none of the methods mentioned above worked for me. In the end, this did the trick for me:
Device.BeginInvokeOnMainThread(() =>
{
myMethod();
});
I found this gem here.
I use Handler with Looper.getMainLooper(). It worked fine for me.
Handler handler = new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(Message msg) {
// Any UI task, example
textView.setText("your text");
}
};
handler.sendEmptyMessage(1);
This is explicitly throwing an error. It says whichever thread created a view, only that can touch its views. It is because the created view is inside that thread's space. The view creation (GUI) happens in the UI (main) thread. So, you always use the UI thread to access those methods.
In the above picture, the progress variable is inside the space of the UI thread. So, only the UI thread can access this variable. Here, you're accessing progress via new Thread(), and that's why you got an error.
For a one-liner version of the runOnUiThread() approach, you can use a lambda function, i.e.:
runOnUiThread(() -> doStuff(Object, myValue));
where doStuff() can represents some method used to modify the value of some UI Object (setting text, changing colors, etc.).
I find this to be much neater when trying to update several UI objects without the need for a 6 line Runnable definition at each as mentioned in the most upvoted answer, which is by no means incorrect, it just takes up a lot more space and I find to be less readable.
So this:
runOnUiThread(new Runnable() {
#Override
public void run() {
doStuff(myTextView, "myNewText");
}
});
can become this:
runOnUiThread(() -> doStuff(myTextView, "myNewText"));
where the definition of doStuff lies elsewhere.
Or if you don't need to be so generalizable, and just need to set the text of a TextView object:
runOnUiThread(() -> myTextView.setText("myNewText"));
For anyone using fragment:
(context as Activity).runOnUiThread {
//TODO
}
This happened to my when I called for an UI change from a doInBackground from Asynctask instead of using onPostExecute.
Dealing with the UI in onPostExecute solved my problem.
I was working with a class that did not contain a reference to the context. So it was not possible for me to use runOnUIThread(); I used view.post(); and it was solved.
timer.scheduleAtFixedRate(new TimerTask() {
#Override
public void run() {
final int currentPosition = mediaPlayer.getCurrentPosition();
audioMessage.seekBar.setProgress(currentPosition / 1000);
audioMessage.tvPlayDuration.post(new Runnable() {
#Override
public void run() {
audioMessage.tvPlayDuration.setText(ChatDateTimeFormatter.getDuration(currentPosition));
}
});
}
}, 0, 1000);
When using AsyncTask Update the UI in onPostExecute method
#Override
protected void onPostExecute(String s) {
// Update UI here
}
This is the stack trace of mentioned exception
at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6149)
at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:843)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.view.View.requestLayout(View.java:16474)
at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:352)
at android.view.View.requestLayout(View.java:16474)
at android.widget.RelativeLayout.requestLayout(RelativeLayout.java:352)
at android.view.View.setFlags(View.java:8938)
at android.view.View.setVisibility(View.java:6066)
So if you go and dig then you come to know
void checkThread() {
if (mThread != Thread.currentThread()) {
throw new CalledFromWrongThreadException(
"Only the original thread that created a view hierarchy can touch its views.");
}
}
Where mThread is initialize in constructor like below
mThread = Thread.currentThread();
All I mean to say that when we created particular view we created it on UI Thread and later try to modifying in a Worker Thread.
We can verify it via below code snippet
Thread.currentThread().getName()
when we inflate layout and later where you are getting exception.
If you do not want to use runOnUiThread API, you can in fact implement AsynTask for the operations that takes some seconds to complete. But in that case, also after processing your work in doinBackground(), you need to return the finished view in onPostExecute(). The Android implementation allows only main UI thread to interact with views.
If you simply want to invalidate (call repaint/redraw function) from your non UI Thread, use postInvalidate()
myView.postInvalidate();
This will post an invalidate request on the UI-thread.
For more information : what-does-postinvalidate-do
Well, You can do it like this.
https://developer.android.com/reference/android/view/View#post(java.lang.Runnable)
A simple approach
currentTime.post(new Runnable(){
#Override
public void run() {
currentTime.setText(time);
}
}
it also provides delay
https://developer.android.com/reference/android/view/View#postDelayed(java.lang.Runnable,%20long)
For me the issue was that I was calling onProgressUpdate() explicitly from my code. This shouldn't be done. I called publishProgress() instead and that resolved the error.
In my case,
I have EditText in Adaptor, and it's already in the UI thread. However, when this Activity loads, it's crashes with this error.
My solution is I need to remove <requestFocus /> out from EditText in XML.
For the people struggling in Kotlin, it works like this:
lateinit var runnable: Runnable //global variable
runOnUiThread { //Lambda
runnable = Runnable {
//do something here
runDelayedHandler(5000)
}
}
runnable.run()
//you need to keep the handler outside the runnable body to work in kotlin
fun runDelayedHandler(timeToWait: Long) {
//Keep it running
val handler = Handler()
handler.postDelayed(runnable, timeToWait)
}
If you couldn't find a UIThread you can use this way .
yourcurrentcontext mean, you need to parse Current Context
new Thread(new Runnable() {
public void run() {
while (true) {
(Activity) yourcurrentcontext).runOnUiThread(new Runnable() {
public void run() {
Log.d("Thread Log","I am from UI Thread");
}
});
try {
Thread.sleep(1000);
} catch (Exception ex) {
}
}
}
}).start();
In Kotlin simply put your code in runOnUiThread activity method
runOnUiThread{
// write your code here, for example
val task = Runnable {
Handler().postDelayed({
var smzHtcList = mDb?.smzHtcReferralDao()?.getAll()
tv_showSmzHtcList.text = smzHtcList.toString()
}, 10)
}
mDbWorkerThread.postTask(task)
}
If you are within a fragment, then you also need to get the activity object as runOnUIThread is a method on the activity.
An example in Kotlin with some surrounding context to make it clearer - this example is navigating from a camera fragment to a gallery fragment:
// Setup image capture listener which is triggered after photo has been taken
imageCapture.takePicture(
outputOptions, cameraExecutor, object : ImageCapture.OnImageSavedCallback {
override fun onError(exc: ImageCaptureException) {
Log.e(TAG, "Photo capture failed: ${exc.message}", exc)
}
override fun onImageSaved(output: ImageCapture.OutputFileResults) {
val savedUri = output.savedUri ?: Uri.fromFile(photoFile)
Log.d(TAG, "Photo capture succeeded: $savedUri")
//Do whatever work you do when image is saved
//Now ask navigator to move to new tab - as this
//updates UI do on the UI thread
activity?.runOnUiThread( {
Navigation.findNavController(
requireActivity(), R.id.fragment_container
).navigate(CameraFragmentDirections
.actionCameraToGallery(outputDirectory.absolutePath))
})
Solved : Just put this method in doInBackround Class... and pass the message
public void setProgressText(final String progressText){
Handler handler = new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(Message msg) {
// Any UI task, example
progressDialog.setMessage(progressText);
}
};
handler.sendEmptyMessage(1);
}
The Error that I receive is "Unfortunately XXXXXX has stopped".Probably something wrong in the onContinue function.
When the progress bar finished it's upload I want him to view the next layout MainScreen.class
Any help will be highly appreciated.
Here is my code:
public class MainActivity extends Activity {
protected static final int TIMER_RUNTIME = 10000; // in ms --> 10s
protected boolean mbActive;
protected ProgressBar mProgressBar;
#Override
public void onCreate(final Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.apploading);
mProgressBar = (ProgressBar)findViewById(R.id.adprogress_progressBar);
final Thread timerThread = new Thread() {
#Override
public void run() {
mbActive = true;
try {
int waited = 0;
while(mbActive && (waited < TIMER_RUNTIME)) {
sleep(200);
if(mbActive) {
waited += 200;
updateProgress(waited);
}
}
} catch(InterruptedException e) {
// do nothing
} finally {
onContinue();
}
}
};
timerThread.start();
}
#Override
public void onDestroy() {
super.onDestroy();
}
public void updateProgress(final int timePassed) {
if(null != mProgressBar) {
// Ignore rounding error here
final int progress = mProgressBar.getMax() * timePassed / TIMER_RUNTIME;
mProgressBar.setProgress(progress);
}
}
public void onContinue() {
// Moved to the Application to the Main Screen
Intent intent = new Intent(this, MainScreen.class);
startActivity(intent);
}
}
You are sleeping in the UI thread, which will cause an ANR. I'm not sure exactly what you are trying to do but if you wish to execute long-running tasks have a look at Asynctask or a Handler.
Also have a read here on keeping your application responsive and avoiding ANRS. Keeping Your App Responsive
Android applications normally run entirely on a single thread by default the "UI thread" or "main thread"). This means anything your application is doing in the UI thread that takes a long time to complete can trigger the ANR dialog because your application is not giving itself a chance to handle the input event or intent broadcasts.
Therefore, any method that runs in the UI thread should do as little work as possible on that thread. In particular, activities should do as little as possible to set up in key life-cycle methods such as onCreate() and onResume(). Potentially long running operations such as network or database operations, or computationally expensive calculations such as resizing bitmaps should be done in a worker thread (or in the case of databases operations, via an asynchronous request).
updateProgress(waited);
can not be executed on your timerThread. All the operations that modify the UI have to be executed on the UI Thread. Use an Handler or runOnTheUiThread
final finalWaited = waited;
runOnUiThread(new Runnable() {
public void run() {
updateProgress(finalWaited);
}
});
I have created IntentService with infinite loop inside the onHandleIntent then add static methods start,resume,pause,stop to directly call it within my Activities.
The scenario is, inside the infinite loop, I am calling callback methods which is creating a new thread to execute long process.
The problem is, I am worrying about continuously creating Threads due to infinite loop. I am pretty sure that there is better way to manage it. I am thinking of ThreadPool or something enable to use only one thread in a sequential manner. So that, I am saving time,memory,overheads etc..
OTHER APPROACH ARE VERY WELCOME. Ask me other information as needed. Then, I will update here.
Here are my codes(take a look at SampleCallback):
IntentService
import android.app.IntentService;
import android.content.Intent;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
public class SampleCallbackIntentService extends IntentService {
private final String LOG_LOGCAT_TAG = "SampleCallbackIntentService";
private Handler _handler;
public SampleCallbackIntentService(String name) {
super(name);
}
#Override
public void onCreate() {
super.onCreate();
// initialize variables for pause & resume thread
_mPauseLock = new Object();
_mPaused = false;
_mFinished = false;
// initialize handler to switch to UI/Main thread
_handler = new Handler()
{
#Override
public void handleMessage(final Message msg)
{
_callback.doSomethingFromUIThread(msg);
}
};
}
private final SampleCallback _callback = new SampleCallback() {
#Override
public void doSomethingFromCurrentThread(final Object object) {
new Thread(new Runnable() {
#Override
public void run() {
//do long running process.
// I will access object here.
}
}).start();
}
#Override
public void doSomethingFromUIThread(final Message msg) {
//may update UI here.
}
};
private final int CALLBACK_MESSAGE = 1;
#Override
protected void onHandleIntent(Intent arg0) {
Log.i(LOG_LOGCAT_TAG, "loop started");
while (!_mFinished) {
// do stuff here
// create the object variable. Then pass to callback method
_callback.doSomethingFromCurrentThread(object);
// process and create the result to pass
String someResult = "some result here";
_handler.sendMessage(_handler.obtainMessage(CALLBACK_MESSAGE, someResult));
synchronized (_mPauseLock) {
while (_mPaused) {
try {
Log.i(LOG_LOGCAT_TAG, "loop paused");
_mPauseLock.wait();
Log.i(LOG_LOGCAT_TAG, "loop resumed");
} catch (InterruptedException e) {
Log.e(LOG_LOGCAT_TAG, "error occured on pause", e);
}
}
}
try {
//using sleep here might be not good design.
Thread.sleep(1000);
} catch (InterruptedException e) {
Log.e(LOG_LOGCAT_TAG, "error occured on sleep", e);
}
}
Log.i(LOG_LOGCAT_TAG, "loop ended");
}
private static Object _mPauseLock;
private static boolean _mPaused;
private static boolean _mFinished;
public static void start(Context context) {
Intent service = new Intent(context, SampleCallbackIntentService .class);
if(context.startService(service)==null) {
Log.e(LOG_LOGCAT_TAG, "Service cannot be started");
} else {
Log.i(LOG_LOGCAT_TAG, "start() called");
}
}
/**
* Call this on pause.
*/
public static void pause() {
Log.i(LOG_LOGCAT_TAG, "pause() called");
synchronized (_mPauseLock) {
_mPaused = true;
}
}
/**
* Call this on resume.
*/
public static void resume() {
Log.i(LOG_LOGCAT_TAG, "resume() called");
synchronized (_mPauseLock) {
_mPaused = false;
_mPauseLock.notifyAll();
}
}
public static void stop() {
if(_mPauseLock == null) return;
synchronized (_mPauseLock) {
Log.i(LOG_LOGCAT_TAG, "stop() called");
_mFinished = true;
}
}
}
SampleCallback
import android.os.Message;
public interface SampleCallback {
public void doSomethingFromCurrentThread(final Object object);
public void doSomethingFromUIThread(final Message msg);
}
UPDATES1
I am using location api aside from google api. I will create a android library project and use that api to get the latest location (e.g. every 2secs) in the background.
On the application side, just need to call static methods to use it (e.g. start(context, callback), pause(), resume(), stop()). It has callbacks to obtain the location. After obtaining the needed information from the location object, I will create a new thread to call my own created callbacks (which implemented by the application side).
You can use AsyncTask instead of creating a new thread every time? AsyncTask manages a fixed pool of threads (or one background thread - depending on Android version) and allows to perform background operations and publish results on the UI thread without having to manipulate threads and/or handlers.
However I wonder why do you need to create an infinite loop inside the onHandleIntent method? By doing that you prevent your IntentService from receiving further Intents. Since in IntentService:
All requests are handled on a single worker thread -- they may take as
long as necessary (and will not block the application's main loop),
but only one request will be processed at a time.
I think you want to execute some long-running code out of the UI thread in the IntentService. But that doesn't require the creation of an infinite loop in the IntentService worker thread. Just send the requests as needed to the IntentService using Context.startService(Intent) call. If you want IntentService to send back some result or just call a callback in the UI thread you can pass a Messenger (or a ResultReceiver) object with the Intent.
Activity:
final Handler uiHandler = new Handler(Looper.getMainLooper());
private void postTask() {
Intent intent = new Intent("com.yourservice.DOACTION");
intent.putExtra("messenger", new Messenger(handler));
intent.putExtra("object", YourObject()); // pass other Parcelable objects
startService(intent);
}
IntentService:
protected void onHandleIntent(Intent intent) {
Messenger messenger = intent.getParcelableExtra("messenger");
YourObject object = intent.getParcelableExtra("object");
//... do work here ...
Message msg = Message.obtain();
msg.what = CALLBACK_MESSAGE;
msg.setData(someResult);
messenger.send(Message.obtain());
}
Look into the docs for ExecutorService (not to be confused with Android Services) and the Executors package. There are a few examples there on how to use thread pools.
So wait, why do you need to use all these callbacks? Can't you just have each intent encode what needs to be done and then have your onHandleIntent execute different code based on the information of the intent. This is the way IntentService is intended to be used.
You shouldn't be doing any of the thread handling in the IntentSerivce. The IntentService is supposed to be handling all the threading code (and you should let it because it's probably highly optimized).