How can I brighten the screen when opening an Acti

问题:

I have a GDK immersion application, where the launcher Activity acquires aSCREEN_DIM_WAKE_LOCK WakeLock. The app also has a Service which will receive chat messages and starts an Intent for an Activity to display each one. Whenever the message Activity is opened, I want to brighten the screen. However, all of the methods I have found do not seem to work.

For example, adding the following into onResume has no effect:

    Settings.System.putInt(getContentResolver(), SCREEN_BRIGHTNESS_MODE, SCREEN_BRIGHTNESS_MODE_MANUAL);

    WindowManager.LayoutParams lp = getWindow().getAttributes();
    lp.screenBrightness = 1.0f;
    getWindow().setAttributes(lp);

To better illustrate the problem, here is the sequence of events in my app:

1. Activity A starts and acquires a SCREEN_DIM_WAKE_LOCK. Activity A dims after a short time.
2. Service B receives a chat message over the network and creates an Intent for Activity C
3. Activity C opens, sets the screen brightness as shown above, but remains dimmed

How can I get the screen to brighten?

回答1:

I was able to find a solution by acquiring a SCREEN_BRIGHT_WAKE_LOCK with the ACQUIRE_CAUSES_WAKEUP flag in onResume. For example:

PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK | PowerManager.ACQUIRE_CAUSES_WAKEUP, "My Tag");
wl.acquire();
//..screen will stay on during this section..
wl.release();

回答2:

Try to put the code before the call to setContentView in onCreate (the brightness level won't update otherwise), something like:

protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  Settings.System.putInt(getContentResolver(), SCREEN_BRIGHTNESS_MODE, SCREEN_BRIGHTNESS_MODE_MANUAL);

  WindowManager.LayoutParams lp = getWindow().getAttributes();
  lp.screenBrightness = 1.0f;
  getWindow().setAttributes(lp);
  // example
  setContentView(R.layout.main);