Android disable button on successful doinbackground call

Question

The following code gives Fatal Exception Async Task #2 on the line v1.setEnabled(false).

It means to disable button on successful call. The v.setEnabled(false); before background task works fine. Please help :(

public void onClick(View v) {
    Intent intent = new Intent(DISPLAY_MESSAGE_ACTION);
    //this one would work
    //v.setEnabled(false);

    final View v1=v;
    mRegisterTask1 = new AsyncTask<Void, Void, Void>() {

    @Override
    protected Void doInBackground(Void... params) {
        boolean success = 
            ServerUtilities.receipt (((String)v1.getTag()).substring(3),"acknowledged");

        if (success) {
            //this one causes Async Task exception
            v1.setEnabled(false);
        } 
        else {
        }
        return null;
    }

    @Override
    protected void onPostExecute(Void result) {
        mRegisterTask1 = null;
    }

You can't change widgets from `doInBackground` as that method runs on a background thread. Either use `runOnUiThread` or post a `Runnable` on `v1` with the `post` method to change the state. — user, Feb 04 '13 at 10:14

score 5 · Answer 1 · answered Feb 04 '13 at 10:16

You can't change the UI state from background thread.
AsyncTask onPreExecute() & onPostExecute() methods called in main thread.
Take a look :

public void onClick(View v) {
    Intent intent = new Intent(DISPLAY_MESSAGE_ACTION);
    //this one would work
    //v.setEnabled(false);


    final View v1=v;
    mRegisterTask1 = new AsyncTask<Void, Void, Boolean>() {

        @Override
        protected Boolean doInBackground(Void... params) {
            boolean success =
                    ServerUtilities.receipt (((String)v1.getTag()).substring(3),"acknowledged");


            return success;
        }

        @Override
        protected void onPostExecute(Bolean result) {

        if (result) {
                //this one causes Async Task exception
                v1.setEnabled(false);
            } else {

            }

            mRegisterTask1 = null;
        }
    }
}

You can set the return parameter of AsyncTask as any Object (Boolean) and not primitives (boolean). — EvZ, Feb 04 '13 at 10:37

score 0 · Accepted Answer · answered Feb 04 '13 at 10:16

Move the ui modification to onPostExecute

boolean success = false;

protected Void doInBackground(Void... params) {
      success = ServerUtilities.receipt (((String)v1.getTag()).substring(3),"acknowledged");

        if (success) {
               //this one causes Async Task exception
                 v1.setEnabled(false);
          } else {

           }
                    return null;
             }
@Override
 protected void onPostExecute(Void result) {
      if (success) {
         //this one causes Async Task exception
            v1.setEnabled(false);
        } else {

        }
       mRegisterTask1 = null;
  }

That works! Now could you explain difference between Void and void? (since void did not work...) — selytch, Feb 04 '13 at 10:36

score 0 · Answer 3 · answered Feb 04 '13 at 10:18

0

You need to change widgets from the UI thread. The methods onProgressUpdate and OnPostExecute are executed in the UI therad. So you may consider to move your code to the latter.

answered Feb 04 '13 at 10:18

Stefan

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Android disable button on successful doinbackground call

3 Answers3

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