onTouchEvent() will not be triggered if setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) is invoked

Question

I call

getWindow().getDecorView().setSystemUiVisibility(View.SYSTEM_UI_FLAG_HIDE_NAVIGATION) 

when my app starts to make my app able to displa

Answer 1

What I've done is first imported android.view.GestureDetector so I can use it to detect gestures. Android has a number of default gestures that are automatically detected in the GestureDector class. Most of this info is found here, but below is code in a form that I've used in an actual project that works.

First I've made an anonymous class in my Activity (this can be nested wherever, but I tend to make my anonymous classes at the bottom, right before the closing bracket). NOTE: You can also implement OnGestureListener as part of your class, also.

The code below is for using gesture detection to give a simple hide/show.

I've declared and defined my action bar (my UI, which is initially hidden) as an instance variable, so I can access it here, and wherever else, but you can substitute it for a getActionBar().show() and getActionBar().hide() in the case you don't want to declare it as an instance variable. Substitute your UI in the place of the actionBar here:

public class Example extends ActionBarActivity {

    // declared in onCreate() method
    private android.support.v7.app.ActionBar actionBar; 
    private GestureDetectorCompat mDetector;
    private YourView view1;
    private YourView view2;
    private YourView view3;
    private YourView view4;

    // some other code

    class GestureListener extends GestureDetector.SimpleOnGestureListener {

    private static final String DEBUG_TAG = "Gestures in Example Class";

        @Override
        public boolean onDoubleTap(MotionEvent event) {

            Log.d(DEBUG_TAG, "onDoubleTap: " + event.toString());
            // if there is a double tap, show the action bar
            actionBar.show();

            return true;
       }

       @Override
       public boolean onSingleTapConfirmed(MotionEvent event) {

            Log.d(DEBUG_TAG, "onSingleTapConfirmed: " + event.toString());

            // if the tap is below the action bar, hide the action bar
            if (event.getRawY() > getResources().getDimension(R.dimen.abc_action_bar_default_height)) {
                actionBar.hide();
                return true;
            }

            return false;
        }

        @Override
        public boolean onDown(MotionEvent event) {

             return true;

        }

} // end-of-Example Class

Then in my onCreate() I've declared my GestureDetector and also (optionally) set my GestureListeners:

private GestureDetectorCompat mDetector;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    // some code here
    mDetector = new GestureDetectorCompat(this, new GestureListener());

    // this code is for more advanced view logic not needed for a basic set-up
    //setGestureListeners();

} // end-of-method onCreate()

Then in order to actually send gestures to be processed we provide the instructions for doing that, there are two ways I know about, first the simplest:

/**
* This method recognizes a touchEvent and passes it to your custom GestureListener 
* class.
*/
@Override 
public boolean onTouchEvent(MotionEvent event){

     this.mDetector.onTouchEvent(event);

     return super.onTouchEvent(event);
}

The second way is more complex, but if you want to only recognize touch events on certain Views in your layout as in the case where you have overlapping views and can only access the top View, you can create a custom class to pass the event around or up:

class MyOnTouchListener implements View.OnTouchListener {

    public boolean onTouch(View v, MotionEvent event) {

        if (v.equals(view4)) {
            return mDetector.onTouchEvent(event);   
        } else return false;
    }
} // end-of-class MyOnTouchListener

and then use it here:

public void setGestureListeners() {

    /* when we return false for any of these onTouch methods
    * it means that the the touchEvent is passed onto the next View.
    * The order in which touchEvents are sent to are in the order they
    * are declared.
    */
    view1.setOnTouchListener(new MyOnTouchListener());

    view2.setOnTouchListener(new MyOnTouchListener());

    view3.setOnTouchListener(new MyOnTouchListener());

    view4.setOnTouchListener(new MyOnTouchListener());


} // end-of-method setGestureListeners()

In my setGestureListeners method, I gave them all the same set of commands, that essentially only recognizes touchEvents on view4. Otherwise, it just passes the touchEvent to the next view.

This is code using AppCompat, but if you are not building for older versions, you can use the regular GestureDetector and ActionBar.