Question

My Question: Is there a work-around for using an onTouchEvent in a FragmentActivity?

My Situation: I’m writing a simple flashlight app and I have a FragmentActivity where a user can swipe between colors (the whole screen is just one color. This app is for personal improvement). I want to be able to do a onLongPress event for options, a onDoubleTap event for hiding the navigation bar, and most importantly a touch event to control brightness of the app (I want to let the user scroll up and down for brightness changes, any ideas here are welcome! is the onFling event good for this?)

What I’ve tried: I have a GestureDetector with my implementation of an SimpleOnGestureListener. I override the onTouchEvent in the FragmentActivity, but I have just found out that this method is never called in a FragmentActivity (I also tested this with a Log.print in the method and it’s never called). Is there a work-around? Thanks!

Salient Code:

MainActivity:

public class MainActivity extends FragmentActivity {

  private GestureDetector gestureDetector;
  private FragmentPagerAdapter mAdapter;

  /**
   * Called when the activity is first created.
   */
  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);
    gestureDetector = new GestureDetector(getApplicationContext(), new MyGestureListener(getWindow()));

    mAdapter = new ColorFragmentAdapter(getSupportFragmentManager(), getDefaultColorList());
    ViewPager pager = (ViewPager) super.findViewById(R.id.viewpager);
    pager.setAdapter(mAdapter);
    pager.setCurrentItem(Math.round(mAdapter.getCount() / 2)); //Set current fragment to middle fragment
  }

  @Override
  public boolean onTouchEvent(MotionEvent event) {
    print("Sending touch event to gestureDetector.");
    //This line is never run.
    return gestureDetector.onTouchEvent(event);
  }

  /**
   * Prints the given object to the log with the debug priority with the tag FLASHLIGHT
   *
   * @param object
   */
  public static void print(Object object) {
    Log.println(Log.DEBUG, "FLASHLIGHT", object.toString());
  }
}

MyGestureListener :

public class MyGestureListener extends SimpleOnGestureListener {

  private final Window window;

  public MyGestureListener(Window window) {
    super();
    this.window = window;
  }

  @Override
  public void onLongPress(MotionEvent e) {
    //onLongPress code
  }

  @Override
  public boolean onDoubleTap(MotionEvent e) {
    //onDoubleTap code
  }

  @Override
  public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY) {
    //onFling cod
  }
}

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical"
  >
  <android.support.v4.view.ViewPager
        android:id="@+android:id/viewpager"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        />
</LinearLayout>

I don’t think you’d need anything else to answer the question, but let me know if you do.

Answer 1

So the solution to this is relatively easy. The problem is that the ViewPager is eating the touch event. So what I did was write my own implementation of a ViewPager and overrided the onTouchEvent(MotionEvent event) method by calling super.onTouchEvent(event) and then passing the event to the gestureDetector within the class.

Relevant Code:

MainActivity

public class MainActivity extends FragmentActivity {

  private FragmentPagerAdapter mAdapter;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.layout_main);
    mAdapter = new FragmentAdapter(getSupportFragmentManager());
    MyViewPager pager = (MyViewPager) findViewById(R.id.viewpager);
    pager.setGestureDetector(new GestureDetector(this, new MyGestureListener(this)));
    pager.setAdapter(mAdapter);
    pager.setCurrentItem(Math.round(mAdapter.getCount() / 2));
  }
}

MyViewPager

public class MyViewPager extends ViewPager {

  private GestureDetector gestureDetector;

  public MyViewPager(Context context) {
    super(context);
  }

  public MyViewPager(Context context, AttributeSet attrs) {
    super(context, attrs);
  }

  @Override
  public boolean onTouchEvent(MotionEvent e) {
    return super.onTouchEvent(e) && gestureDetector.onTouchEvent(e);
  }
}

MyGestureListener

public class MyGestureListener extends SimpleOnGestureListener {

  private final Activity activity;

  public MyGestureListener(Activity activity) {
    super();
    this.activity = activity;
  }

  @Override
  public boolean onDoubleTap(MotionEvent e) {
    //...
  }

  @Override
  public boolean onSingleTapConfirmed(MotionEvent e) {
    //...
  }

//... etc...

}

layout_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
  xmlns:android="http://schemas.android.com/apk/res/android"
  android:layout_width="fill_parent"
  android:layout_height="fill_parent"
  android:orientation="vertical"
>
  <com.kentcdodds.flashlight.MyViewPager
    android:id="@+android:id/viewpager"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
        />
</LinearLayout>