Extended GestureDetector functionality. Adds onScrollEnd method.

ExtendedGestureDetector.java

import android.content.Context;
import android.os.Build;
import android.support.annotation.RequiresApi;
import android.view.GestureDetector;
import android.view.MotionEvent;

/**
 * Improved android's {@link android.view.GestureDetector}
 *
 * Features:
 * - adds {@link ExtendedSimpleGestureListener#onScrollEnd(MotionEvent)}, so that end of 
 * the scroll can be detected.
 */
public class ExtendedGestureDetector {
	private ExtendedSimpleGestureListener mExternalListener;
	/** Listener used for re-routing Android's 
	 * {@link android.view.GestureDetector.SimpleOnGestureListener} callbacks to external 
	 * {@link ExtendedSimpleGestureListener}*/
	private ListenerRouter mListenerRouter;
	private ModifiedDetector mModifiedDetector;

	public ExtendedGestureDetector(Context context, ExtendedSimpleGestureListener
			extendedSimpleGestureListener){
		mExternalListener = extendedSimpleGestureListener;

		mListenerRouter = new ListenerRouter();

		mModifiedDetector = new ModifiedDetector(context, mListenerRouter);
	}

	public boolean onTouchEvent(MotionEvent motionEvent){
		return mModifiedDetector.onTouchEvent(motionEvent);
	}

	/**
	 * Class that adds additional functionality to {@link GestureDetector}.
	 * 
	 * Needed so we can detect and trigger custom callbacks from 
	 * {@link ExtendedSimpleGestureListener}.
	 */
	private class ModifiedDetector extends GestureDetector {
		ModifiedDetector(Context context, OnGestureListener listener) {
			super(context, listener);
		}

		@Override
		public boolean onTouchEvent(MotionEvent ev) {
			boolean handled = super.onTouchEvent(ev);

			switch(ev.getAction()){
				case MotionEvent.ACTION_UP:
					if(mListenerRouter.isScrolling)
						mListenerRouter.onScrollEnd(ev);
					break;
			}

			return handled;
		}
	}

	/** 
	 * Class for adding additional functionality to 
	 * {@link android.view.GestureDetector.SimpleOnGestureListener}
	 */
	public static class ExtendedSimpleGestureListener extends GestureDetector
			.SimpleOnGestureListener {
		/**
		 * Called when scrolling ended.
		 * @param me {@link MotionEvent#ACTION_UP} motion event
		 */
		public void onScrollEnd(MotionEvent me){ }
	}


	/**
	 * Listener re-routing class. Passes detected gesture events from Android's 
	 * {@link android.view.GestureDetector.OnGestureListener} and 
	 * {@link ExtendedSimpleGestureListener} to {@link #mExternalListener}.
	 */
	private class ListenerRouter extends ExtendedSimpleGestureListener {
		private boolean isScrolling = false;

		@Override public boolean onSingleTapUp(MotionEvent e) {
			return mExternalListener.onSingleTapUp(e);
		}

		@Override public void onLongPress(MotionEvent e) {
			mExternalListener.onLongPress(e);
		}

		@Override public boolean onScroll(MotionEvent e1, MotionEvent e2,
				float distanceX, float distanceY) {
			isScrolling = true;
			return mExternalListener.onScroll(e1, e2, distanceX, distanceY);
		}

		@Override public void onScrollEnd(MotionEvent me) {
			isScrolling = false;
			mExternalListener.onScrollEnd(me);
		}

		@Override public boolean onFling(MotionEvent e1, MotionEvent e2, float velocityX,
				float velocityY) {
			return mExternalListener.onFling(e1, e2, velocityX, velocityY);
		}

		@Override public void onShowPress(MotionEvent e) {
			mExternalListener.onShowPress(e);
		}

		@Override public boolean onDown(MotionEvent e) {
			isScrolling = false; // Just in case
			return mExternalListener.onDown(e);
		}

		@Override public boolean onDoubleTap(MotionEvent e) {
			return mExternalListener.onDoubleTap(e);
		}

		@Override public boolean onDoubleTapEvent(MotionEvent e) {
			return mExternalListener.onDoubleTapEvent(e);
		}

		@Override public boolean onSingleTapConfirmed(MotionEvent e) {
			return mExternalListener.onSingleTapConfirmed(e);
		}

		@RequiresApi(api = Build.VERSION_CODES.M)
		@Override public boolean onContextClick(MotionEvent e) {
			return mExternalListener.onContextClick(e);
		}
	}
}