update ui in thread

Question

I create a class and extend it from view. also implemented the Runnable interface. In the onTouchEvent i call: new Thread(this).start().
This is my class:

public class test extend View interface Runnable{

    ----some code------

    public void onTouchEvent(MotionEvent event){
        ----somecode------
        new thread(this).start();
        ----somecode------
    }

    public void run(){
        -----somecode-------
        invalidate();
        -----somecode-------
    }
}

but i receive this error:

only the original thread that created a view hierarchy can touch its views

How can i fix this?

Take a look at http://stackoverflow.com/questions/4369537/update-ui-from-thread - the chosen should solution should help you — Elemental, Dec 17 '12 at 14:25

Berťák · Answer 1 · 2012-12-17T14:39:30.300

1

you need to update UI on UIThread, use

Activity activity = (Activity)getContext();
activity.runOnUiThread(new Runnable() {
    @Override
    public void run() {
        // update UI here
        invalidate();
    }
});

edited Dec 17 '12 at 14:39

answered Dec 17 '12 at 14:24

Berťák

7,143
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but. runOnUiThread work on Activity. i'm in View(my class extended from View Class). – Rasoul Taheri Dec 17 '12 at 14:29
if you create your view by constructor, where you pass your activity as a context(`MyView myView = new MyView(MyActivity.this)`), you can get that activity by calling `Activity activity = (Activity)getContext();` in your view – Berťák Dec 17 '12 at 14:33

ibit · Accepted Answer · 2012-12-17T14:44:50.277

1

Try to use

postInvalidate()

instead of

invalidate()

edited Dec 17 '12 at 14:44

answered Dec 17 '12 at 14:31

ibit

316
1
6

score 0 · Answer 3 · edited May 23 '17 at 12:18

0

You can use handler class to make changes on your UI thread by sending messages.

http://developer.android.com/reference/android/os/Handler.html

Android, Handler messaging

edited May 23 '17 at 12:18

Community

1
1

answered Dec 17 '12 at 14:26

Damask

1,754
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score 0 · Answer 4 · answered Dec 17 '12 at 14:35

Since you are extending View class which binds to UI-thread, so anything you call in this class will run on the UI-thread. However, if you are using a new thread inside that class, then you may rely on its post(Runnable) method which will guarantee to run on the view's UI-thread. For example:

post(new Runnable() {

    @Override
    public void run() {
        // TODO Auto-generated method stub

    }
});

score 0 · Answer 5 · answered Dec 17 '12 at 14:36

0

this will run on UI thread from View class;

  post(new Runnable() {     
        @Override
        public void run() {
            // TODO Auto-generated method stub

        }
    });

answered Dec 17 '12 at 14:36

Mohammad Ersan

12,304
8
54
77

score 0 · Answer 6 · answered Dec 26 '12 at 12:53

Try AsyncTask in android. It start new thread asynchronously and after completion of task it can update current UI without destroying current Activity.

Example Code :

private class DownloadFilesTask extends AsyncTask<URL, Integer, Long> {
 protected Long doInBackground(URL... urls) {
     // Task which should be completed in background.
     return null;
 }

 protected void onProgressUpdate(Integer... progress) {
     // Task which can be done while background process is progressing , such as updatng any UI element of Activity.
     setProgressPercent(progress[0]);
 }

 protected void onPostExecute(Long result) {
     // Task to do after completion of asynctask.
     showDialog("Downloaded " + result + " bytes");
 }
}

You may also use runOnUiThread to do your task.

Both ways are very effective in updating UI in current activity.

Useful Link : http://developer.android.com/reference/android/os/AsyncTask.html http://sharecoding.wordpress.com/2012/05/22/simple-runonuithread-for-update-view-on-android/

update ui in thread

6 Answers6