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 have the following thread with a constructor in my service class.
public class communicationDetails extends Thread {
communicationDetails(final Handler _handler, final Handler conn_handler) throws IOException {
mhandler = _handler;
connHandler = conn_handler;
}
In onCreate in my service I tried to construct the thread and start it.First handler works fine, I could able to send messages. Since I want to post a message with delay, in the second handler I am trying to use postDelay method. This is where the problem comes in.
try {
communication_Details = new communicationDetails(
// works fine
new Handler(Looper.getMainLooper()) {
#Override
public void handleMessage(final Message msg) {
// sending messages
}
},
//this throws an error
new Handler(Looper.getMainLooper()).postDelayed(new Runnable() {
#Override
public void run() {
// call a method
}
}, 2000));
} catch (IOException e) {
e.printStackTrace();
}
communication_Details.start();
I get following error. What stupid mistake am I doing here ? or is it completely wrong approach.
error: incompatible types: boolean cannot be converted to Handler
The error : incompatible types is because :-
handler.postDelayed(runnable) --> returns boolean
while the constructor requires object of type android.os.Handler
So you are basically passing boolean instead of an instance of Handler
For more info checkout android.os.Handler. ( cmd + click ) on Handler
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);
}
So I have a question, and if it's a stupid one I do apologize up front, I have tried to search for it but not sure what to search for exactly. I am trying to run a delayed task, but only if my int = 0, would this work correctly like I am wanting it to?
public static void runTask(String p)
{
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run()
{
pendingRequest = pendingRequest - 1;
if (pendingRequest == 0)
{
context.startActivity(p);
}
}
}, 4000);
}
}
What I want it to do is only run if pendingRequest is 0, but I have other activities that add to pending request after the runTask() is called. If this doesn't make any sense please let me know and I will try to reword it.
This is a bit of an obscure way to do things so seeing just this snippet I cant tell exactly what the desired behavior is, however, it should work if you make the parameter "p" final. Im also not familiar with a startActivity method that takes a string instead of an intent, but I cant tell if "context" is actually an Android Context object, but I'm assuming it is.
What I'm not sure about is why you would wait 4 seconds BEFORE decrementing pendingRequest. I would think you want to decrement, allow 4 seconds for someone else to add a pending request, and if it's still 0 after the wait start the Activity... but, again, I cant tell from the snippet.
Try this:
private static Object requestLock = new Object();
public static void runTask(final String p)
{
synchronized(requestLock)
{
if (--pendingRequest > 0) // Decrement first
{
// There are more requests
return;
}
}
// Wait 4 sec and if there are still no requests start the activity.
Handler handler = new Handler();
handler.postDelayed(new Runnable() {
#Override
public void run()
{
synchronized(requestLock)
{
if (pendingRequest == 0)
{
context.startActivity(p);
}
}
}
}, 4000);
}
}
Note: You will also need to add a synchronized block where you increment the pendingRequests.
Can anyone point me in the right direction here please ?
I have an activity which spawns two threads, a thread for handling messages, using a Looper
public static class MiddleThread extends Handler{
static public Handler handler;
public void run() {
Looper.prepare();
Log.d("MiddleThread", "Looper is prepared !");
handler = new Handler() {
public void handleMessage(Message msg)
{
Bundle bundle = msg.getData();
String exitString = bundle.getString("endmessage");
if(exitString.equals(("ExitOK")))
{
boolean searchFinished = true;
Looper looper = Looper.myLooper();
looper.quit();
} else
{
int fileCount = bundle.getInt("filecount");
String fileName = bundle.getString("filename");
Log.d("MiddleThread", "File Number " + fileCount + " is " + fileName);
}
}
};
Log.d("MiddleThread", "nandler should be initialised");
Looper.loop();
}
... then it spawns the main Worker Thread, which is passed a handler from the UI Thread, and the handler from the above thread.
public class BasicSearch {
public Handler handlerUi, handlerMiddleThread;
public Message messageUi, messageMiddleThread;
public int fileCount = 0;
public BasicSearch(Handler ui, Handler mt) {
handlerUi = ui;
handlerMiddleThread = mt;
}
public void listFiles()
{
File searchPath = Environment.getExternalStorageDirectory();
messageUi = handlerUi.obtainMessage();
messageMiddleThread = handlerMiddleThread.obtainMessage();
walk(searchPath);
Bundle b = new Bundle();
b.putString("endmessage", "ExitOK");
messageMiddleThread.setData(b);
handlerMiddleThread.dispatchMessage(messageMiddleThread);
}
private void walk(File path) {
File[] list = path.listFiles();
for(File f : list)
{
if(f.isDirectory())
{
walk(new File(f.getAbsolutePath()));
} else {
processFile(f);
}
}
}
private void processFile(File f) {
Bundle b = new Bundle();
fileCount++;
b.putString("filename", f.getName());
b.putInt("filecount", fileCount);
messageMiddleThread.setData(b);
Log.d("BasicSearch", "Data is set, to send to MiddleThread");
handlerMiddleThread.dispatchMessage(messageMiddleThread);
Log.d("BasicSearch", "Message sent");
}
}
Whatever happens, when it tries to dispatchMessage, handlerMiddleThread reverts to being null. I even have the following code in my activity, to try and ensure that it isn't null, but it still ends up being null when I get to send the message.
startMiddleThread();
while(true)
{
if(MiddleThread.handler != null)
break;
}
startSearchThread();
This is a test project, as I wanted to be able to get the Handler/Looper concept properly understood before continuing on with my project.
I have successfully managed to use a Handler in my UI Threads before, but my current project has too much processing going on in the UI, and I want to have a secondary thread handling the output from the searchThread, and just receive a message in UI thread when the thread is complete.
So I think I see what you're trying to do and let me suggest a slightly easier way:
To start your background thread and get a handler to it:
HandlerThread bgThread = new HandlerThread();
bgThread.start();
Handler bgHandler = new Handler(bgThread.getLooper());
Then you can send whatever messages you want to your bgHandler. Note that you need to call start on a HandlerThread before creating the bgThread (otherwise getLooper() will return null).
That being said I think I know whats wrong with your code as you posted it. First, MiddleThread extends Handler (which doesn't have a run() method!) not Thread. Second, the run() method on MiddleThread is never called, so Handler is never instantiated. Even if your just mistyped Handler in your code above and you're actually extending Thread, you still need to call start on MiddleThread in order for anything in run() to be executed. Really though, what you're doing is waaay more complicated that it needs to be, and you almost certainly want to just do what I mentioned above.