Question

Hi im developing an android application and im wondering how i make the app use less CPU while backgrounded. For example, my application pauses once it loses focus but the cpu usage is still 50%

Edit

 while (!pause) {
             Canvas c = null;
             try {
                 c = sHolder.lockCanvas(null);
                 synchronized (sHolder) {
                     doDraw(c);
                     powerUps();
                 }
             } finally {
                 if (c != null) {
                     sHolder.unlockCanvasAndPost(c);
                 }
             }
         }

Then when you pause and resume it just changes the pause variable

Answer 1

IMO, you should not be looping at all while your app is paused.

See this page for more details about the “proper” lifecycle of an android app.

Also note that with any busy loop design your app will be using 100% of the CPU – I’m not sure if starting a loop from the onResume() method is correct; my instinct is to have each iteration of your loop performed by a separate call initiated by a call to Handler.post(), with the last statement re-posting the next call. Otherwise, the application’s main thread will be starved, right?

Maybe something like this:

void iterate() {
     Canvas c = null;
     try {
         c = sHolder.lockCanvas(null);
         synchronized (sHolder) {
             doDraw(c);
             powerUps();
         }
     } finally {
         if (c != null) {
             sHolder.unlockCanvasAndPost(c);
         }
     }
     this.handler.post(this.iterateRunnable);
}

void onResume() {
    this.handler = new Handler();
    this.iterateRunnable = new Runnable() {
        @Override public void run() { iterate(); }
    };
    this.handler.post(this.iterateRunnable);
}