Question

My app has a screen that refreshes every second in AsyncTask:

class BarRefresh extends AsyncTask<Void, Void, Void>{
    @Override
    protected Void doInBackground(Void... params) {
       // doSomething();
        while(redraw){
            for(int i = 0; i < c.sets.size(); i++)
            {
                vals[i] = c.sets.get(i).getLast();
            }
            graph.updateVals(vals);
            graph.postInvalidate();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            if(isCancelled()){
                break;
            }
        }
        return null;
    }
}

A click on one of the objects opens a new activity with a parameter:

@Override
        public boolean onTouch(View v, MotionEvent ev) {
            // TODO Auto-generated method stub
            float[] coords = new float[2];
            coords[0] = ev.getX();
            coords[1] = ev.getY();
            int set = 0;
            for(int i = 0; i < graph.values.length; i++){
                if(graph.rects[i].contains(coords[0], coords[1]))
                {
                    redraw = false;
                    Bundle chosen = new Bundle();
                    chosen.putInt("set", i);
                    Intent bb = new Intent(GraphTestActivity.this, LineGraphActivity.class);
                    bb.putExtras(chosen);
                    startActivity(bb);
                //  set = i;
                }
            }
            //Toast t = Toast.makeText(GraphTestActivity.this, "KLIKNIETO " + set, Toast.LENGTH_SHORT);
            //t.show();
            return false;
        }

In the new activity constructor looks like that:

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    Bundle pick = getIntent().getExtras();
    setNr = pick.getInt("set");
    c = Common.getInstance();
    set = c.sets.get(setNr);
    graph = new LineGraph(LineGraphActivity.this, set);
    setContentView(graph);
}

Here is where things get weird. On the emulator everything works fine (app is on 2.1 API, so is the emulator), but when I load it up on my phone, five or more instances of the second activity open at the same time and I have to press back button multiple times to go back to the original screen.

My phone is Samsung i5700 Spica with And 2.3.7 (Cyanogen 7.2 NIGHTLY alpha)

Answer 1

You are probably getting multiple onTouch() events. Verify this through the debugger. on the emulator it’s quite boolean, but on a real touch screen in the micro seconds as your finger is coming in contact with the screen you can receive multiple touch events.

If you can use a higher-level function like onClick instead of onTouch, do that. If you can’t you need to keep track of the touch down and touch up events and only react to down if it wasn’t already down.

A hack would be to define your activity as single instance, then you won’t get multiple instances. This is almost certainly not the right thing to do though.

As a side note, putting Thread.sleep() in your code almost always indicates a lurking bug, and that the code is written incorrectly. If you need something to happen at a later point in your code, use Handler.postDelayed() or a Timer.