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 an if statement which checks if three slots are finished. If it is, the timer should stop, but the code is not running for some reason. I have seen a post similar to this If-condition never executes despite correct condition, however their solution solved nothing.
Here is my code:
Stop function
public void stop(ImageSwitcher slot){
slotOneFinished = (slot.equals(slotOne));
slotTwoFinished = (slot.equals(slotTwo));
slotThreeFinished = (slot.equals(slotThree));
if (slotOneFinished&&slotTwoFinished&&slotThreeFinished){
//not running
Toast.makeText(MainActivity.this, "Running",Toast.LENGTH_SHORT).show();
checkWin(getFruits());
timer.cancel();
timer = null;
}
}
Timer
private Timer timer;
TimerTask timerTask = new TimerTask() {
#Override
public void run() {
runOnUiThread(new TimerTask() {
#Override
public void run() {
if (!slotOneFinished){
animate(randomSwitchCount(), slotOne);
}
if (!slotTwoFinished) {
animate(randomSwitchCount(), slotTwo);
}
if (!slotThreeFinished) {
animate(randomSwitchCount(), slotThree);
}
}
});
}
};
Animate function
public void animate(final int maxCount, final ImageSwitcher slot) {
i++;
if (i<maxCount){
Animation in = AnimationUtils.loadAnimation(this, R.anim.new_slot_item_in);
Animation out = AnimationUtils.loadAnimation(this, R.anim.old_item_out);
slot.setInAnimation(in);
slot.setOutAnimation(out);
int fruit = randomFruit();
slot.setTag(fruit);
slot.setImageResource(fruit);
}else {
stop(slot);
}
}
Using == did nothing as well.
Thanks for your help,
PiNet
This condition can never be true, assuming that equals() is implemented in the canonical way, and slotOne, slotTwo, and slotThree are 3 distinct objects:
if (slotOneFinished&&slotTwoFinished&&slotThreeFinished)
Looks like you had a mistaken assumption about the scope of the variables. You can probably fix this by using a condition like this, instead:
if( slot == slotOne )
slotOneFinished = true;
...and so forth.
The Android Studio debugger is your friend.
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 got a listView that gets populated from a server. In the onClick of the ListItem, I display a button for a x number of seconds and I make it invisible again. How can I reset the time every time the onClick is called?
Here is my listItem onClick:
private void displayInCallButton() {
mButton.setEnabled(true);
if (canDisplayInCallControlls) {
canDisplayInCallControlls = false;
fadeInAnimation(mButton);
mButton.setEnabled(true);
mFrontView.postDelayed(new Runnable() {
public void run() {
fadeOutAnimation(mButton);
mButton.setEnabled(false);
hasAnimationEnded = true;
canDisplayInCallControlls = true;
}
}, 5000);
}
}
Thank you in advance.
You have to remove the callbacks and set it once again with the new one with the reset time.
first, set the call back like
Runnable myRunnable = new Runnable() {
#Override
public void run() {
fadeOutAnimation(mButton);
mButton.setEnabled(false);
hasAnimationEnded = true;
canDisplayInCallControlls = true;
}
};
then set it to mFrontView like,
mFrontView.postDelayed(myRunnable,5000)
If you want to reset, do it like
mFrontView.removeCallbacks(myRunnable);
mFrontView.postDelayed(myRunnable, 2000);
How can I reset the time every time the onClick is called?
There is no built-in mechanism to accomplish that.
You can, however, keep a reference to the Runnable you post, remove it and then repost it again to restart at the original delay.
The result would look somewhat like this in its most simple form:
Runnable mDelayedRunnable = new Runnable() {
#Override public void run() {
fadeOutAnimation(mButton);
mButton.setEnabled(false);
hasAnimationEnded = true;
canDisplayInCallControlls = true;
}
};
private void displayInCallButton() {
mButton.setEnabled(true);
if (canDisplayInCallControlls) {
canDisplayInCallControlls = false;
fadeInAnimation(mButton);
mButton.setEnabled(true);
mFrontView.removeCallbacks(mDelayedRunnable);
mFrontView.postDelayed(mDelayedRunnable, 5000);
}
}
You can safely call removeCallbacks() with a Runnable that was never posted in the first place (or even null).
If you don't want to keep an explicit reference to the Runnable, you could also opt to tag the view with it. Just don't forget to clean up on i.e. orientation changes and the like.