Helper to handle swipe gestures on Android

OnSwipeTouchListener.java

/* -*- Mode:jde; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
/**
 * Copyright (c) 2015 Regents of the University of California
 *
 * This file is part of NFD (Named Data Networking Forwarding Daemon) Android.
 * See AUTHORS.md for complete list of NFD Android authors and contributors.
 *
 * NFD Android is free software: you can redistribute it and/or modify it under the terms
 * of the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * NFD Android is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * NFD Android, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.named_data.nfd.util;

import android.content.Context;
import android.view.GestureDetector;
import android.view.GestureDetector.SimpleOnGestureListener;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;

/**
 * @brief Helper to handle right to left swipe gestures
 * Based on code by Mirek Rusin (http://stackoverflow.com/a/12938787/2150331)
 */
public class OnSwipeTouchListener implements OnTouchListener {

  public
  OnSwipeTouchListener(Context ctx)
  {
    m_gestureDetector = new GestureDetector(ctx, new GestureListener());
  }

  public boolean
  onTouch(final View view, final MotionEvent motionEvent)
  {
    m_view = view;
    return m_gestureDetector.onTouchEvent(motionEvent);
  }

  private final class GestureListener extends SimpleOnGestureListener {

    private static final int SWIPE_THRESHOLD = 100;
    private static final int SWIPE_VELOCITY_THRESHOLD = 100;

    @Override
    public boolean
    onDown(MotionEvent e)
    {
      return true;
    }

    @Override
    public boolean
    onFling(MotionEvent e1, MotionEvent e2, float velocityX, float velocityY)
    {
      boolean result = false;
      try {
        float diffY = e2.getY() - e1.getY();
        float diffX = e2.getX() - e1.getX();
        if (Math.abs(diffX) > Math.abs(diffY)) {
          if (Math.abs(diffX) > SWIPE_THRESHOLD && Math.abs(velocityX) > SWIPE_VELOCITY_THRESHOLD) {
            if (diffX > 0) {
              onSwipeRight(m_view);
            } else {
              onSwipeLeft(m_view);
            }
          }
          result = true;
        }
        else if (Math.abs(diffY) > SWIPE_THRESHOLD && Math.abs(velocityY) > SWIPE_VELOCITY_THRESHOLD) {
          if (diffY > 0) {
            onSwipeBottom(m_view);
          } else {
            onSwipeTop(m_view);
          }
        }
        result = true;

      } catch (Exception exception) {
        exception.printStackTrace();
      }
      return result;
    }
  }

  /**
   * @brief Override to process swipe-right event
   */
  public void onSwipeRight(View view)
  {
  }

  /**
   * @brief Override to process swipe-left event
   */
  public void onSwipeLeft(View view)
  {
  }

  /**
   * @brief Override to process swipe-top event
   */
  public void onSwipeTop(View view)
  {
  }

  /**
   * @brief Override to process swipe-bottom event
   */
  public void onSwipeBottom(View view)
  {
  }

  /////////////////////////////////////////////////////////////////////////////
  private final GestureDetector m_gestureDetector;
  private View m_view;
}