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I am writing a small game for Android. The game is drawn on a SurfaceView using a Thread. Within the run() method of the Thread, I test to see if the game is over and if it is, I try to display the game over dialog however that gives me the forementioned error message. I know that this error occurs when a non-UI thread tries to mess with the UI. What I'd like to know is the best approach to displaying such a dialog. I've pasted the code below. Thanks for your help:

public class BouncingBallActivity extends Activity{

    private static final int DIALOG_GAMEOVER_ID = 0;
    private BouncingBallView bouncingBallView;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        bouncingBallView = new BouncingBallView(this);
        bouncingBallView.resume();
        setContentView(bouncingBallView);
    }

    protected Dialog onCreateDialog(int id)
    {
        switch (id) {
        case DIALOG_GAMEOVER_ID:
            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.setMessage("Game Over.")
                    .setCancelable(false)
                    .setPositiveButton("Try Again",
                            new DialogInterface.OnClickListener()
                                {

                                public void onClick(DialogInterface arg0,
                                        int arg1)
                                {
                                    bouncingBallView.resume();

                                }
                            })
                    .setNegativeButton("Exit",
                            new DialogInterface.OnClickListener() {

                                public void onClick(DialogInterface dialog,
                                        int which)
                                {
                                    BouncingBallActivity.this.finish();

                                }
                            });

            AlertDialog gameOverDialog = builder.create();
            return gameOverDialog;
        default:
            return null;
        }


    }


    class BouncingBallView extends SurfaceView implements Runnable
    {
        SurfaceHolder   surfaceViewHolder;
        Canvas          canvas;
        Context         context;
        Thread          drawingThread;

        boolean         drawingThreadIsRunning;
        boolean         isInitialised;

        Ball            ball;
        ArtificialIntelligence ai;

        BouncingBallView(Context context)
        {
            //
        }

        public void pause()
        {
            isInitialised = false;
            drawingThreadIsRunning = false;
            boolean joiningWasSuccessful = false;

            while(!joiningWasSuccessful)
            try {
                drawingThread.join();
                joiningWasSuccessful = true;
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

        }

        public void resume()
        {
            isInitialised = false;
            drawingThread = new Thread(this);

            drawingThread.setName("Drawing Thread");
            drawingThreadIsRunning = true;
            drawingThread.start();

        }

        public void run()
        {
            while(drawingThreadIsRunning)
            {
                if(!surfaceViewHolder.getSurface().isValid())
                    continue;

                if(gameOver())
                    BouncingBallActivity.this.showDialog(DIALOG_GAMEOVER_ID);

                try{
                    canvas = surfaceViewHolder.lockCanvas();
                    if(!isInitialised)init(canvas);
                    update();
                    surfaceViewHolder.unlockCanvasAndPost(canvas);
                }catch(Exception e)
                {
                    Log.e(BouncingBallActivity.this.toString(),String.format("%s: Just as the emperor had foreseen!\n(This error is expected. Canvas destroyed while animations continue.)", e.toString()));
                }
            }
        }

        private void init(Canvas canvas)
        {
            ball = new Ball(canvas, Color.GREEN);
            ai   = new ArtificialIntelligence(canvas, (int) (ball.getX()+100),canvas.getWidth());

            isInitialised = true;
        }

    }
}
W.K.S
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4 Answers4

2

Try like this... you cannot make any changes to ui from other than main thread..put this part inside your thread after if(gameOver())

//if(gameOver())
 runOnUiThread(new Runnable() {
           @Override
           public void run() {

               BouncingBallActivity.this.showDialog(DIALOG_GAMEOVER_ID);
           }
       });
5hssba
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  • Thanks a mill! Worked like a charm :) – W.K.S Mar 27 '12 at 12:16
  • I'm having a problem using this. Because it's within the thread, multiple dialogs keep appearing. Is there a way around that? – W.K.S Mar 27 '12 at 14:23
  • declare an int variable at beginning..and after you display dialog once.. increment it.. and check its value before displaying like this..if(variable=0){BouncingBallActivity.this.showDialog(DIALOG_GAMEOVER_ID);variable++;} – 5hssba Mar 28 '12 at 04:10
  • I tried several versions of that including the way you just mentioned. It doesn't work for some reason :/ – W.K.S Mar 29 '12 at 11:53
  • you mean the thread is running continuously or getting some error? – 5hssba Mar 29 '12 at 11:58
  • No, I mean that even with a flag to see if the dialog has already been displayed, two dialogs appear. When you close one, a second one is there behind it. – W.K.S Mar 29 '12 at 12:43
1

You are calling the Dialog from the worker(background) thread. You need to call this from the main thread. Try calling it using Activity.runOnUIThread() and create a handler inside that, which will call your showDialog method.

Mimminito
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0

I used [https://stackoverflow.com/a/16886486/3077964] to solve the issue.

You need to pause the BouncingBallView's thread after showing the dialog inside the runOnUiThread(). That is:

//if(gameOver()){       
BouncingBallActivity.this.runOnUiThread(new Runnable() {
 @Override
public void run() {    BouncingBallActivity.this.showDialog(DIALOG_GAMEOVER_ID);    }    });    pause();    }
Community
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Padhu
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For me i have used this handler in my surfaceView to create the dialogBox. 

Handler someHandler = new Handler(){
//this method will handle the calls from other threads. 
public void handleMessage(Message msg) {

                 final Dialog dialog = new Dialog(Game.this);

                   dialog.setContentView(R.layout.question_dialog);
                   dialog.setTitle("GAME OVER");




                   Button restart=(Button)dialog.findViewById(R.id.btn Restart);

                   // Set On ClickListener
                   restart.setOnClickListener(new View.OnClickListener() {

                       public void onClick(View v) {


                               Toast.makeText(Game.this, "Restart Game", Toast.LENGTH_LONG).show();
                               dialog.dismiss();

                           }


                       }
                   });

                   dialog.show();

             }

So, i write the looper.prepared() in the game thread to call this Handler. If the player power = 0, this dialogBox will appear.

Looper.prepare();

 //create the message for the handler 
 Message status = someHandler.obtainMessage();
 Bundle data = new Bundle();
 String msgContent = null;
 data.putString("SOMETHING", msgContent);
 status.setData(data);
 someHandler.sendMessage(status);

 Looper.loop();

  }
Vetzehelza
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