javafx android FLAG_KEEP_SCREEN_ON

Question

In my app, I need to make sure the android device's screen stays on when the user clicks a button. When the use clicks another button, I want to allow the screen to turn off when it normally would. To do this, I need to call: getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

The android documentation states that this call must be made from an activity, which is what I've done. Here is my code snippet:

public class AndroidDataProvider implements DataProvider {
    @Override
    public void keepScreenOn(boolean flag) {
        if(flag) {
            Window window = FXActivity.getInstance().getWindow();
            window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        }
        else {
            Window window = FXActivity.getInstance().getWindow();
            window.clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        }
    }
}

When I run this code on my Samsung Galaxy S5 and S6, I get an exception. The code to keep the screen on works when I run it natively in android studio, so that's not the issue. Any idea how to get this functionality to work? wake lock will not work because I need to enable and disable this functionality based on UI events.

score 0 · Accepted Answer · edited May 23 '17 at 11:53

If you check the exception (./adb logcat -v threadtime):

AndroidRuntime: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
AndroidRuntime:     at android.view.ViewRootImpl.checkThread(ViewRootImpl.java:6855)
AndroidRuntime:     at android.view.ViewRootImpl.requestLayout(ViewRootImpl.java:1040)
AndroidRuntime:     at android.view.View.requestLayout(View.java:19657)
AndroidRuntime:     at android.view.View.setLayoutParams(View.java:13247)
AndroidRuntime:     at android.view.WindowManagerGlobal.updateViewLayout(WindowManagerGlobal.java:365)
AndroidRuntime:     at android.view.WindowManagerImpl.updateViewLayout(WindowManagerImpl.java:99)
AndroidRuntime:     at android.app.Activity.onWindowAttributesChanged(Activity.java:2867)
AndroidRuntime:     at android.view.Window.dispatchWindowAttributesChanged(Window.java:1098)
AndroidRuntime:     at com.android.internal.policy.PhoneWindow.dispatchWindowAttributesChanged(PhoneWindow.java:2998)
AndroidRuntime:     at android.view.Window.setFlags(Window.java:1075)
AndroidRuntime:     at android.view.Window.addFlags(Window.java:1033)

the message Only the original thread that created a view hierarchy can touch its views will give you enough information. If you check this question, you just need to move your code to the main thread:

    FXActivity.getInstance().runOnUiThread(() -> {
        Window window = FXActivity.getInstance().getWindow();
        if (flag) {
            window.addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        } else {
            window.clearFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        }
    });

Thanks Jose. The code worked except that I had to replace the lambda with the old style method. — Harry Mitchell, Nov 27 '16 at 21:28
That shouldn't be required... as Retrolambda is applied to the Android package as well — José Pereda, Nov 27 '16 at 21:33

javafx android FLAG_KEEP_SCREEN_ON

1 Answers1