RotateGestureDetector.java

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/*
 * Copyright (C) 2012 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package org.ros.android.view.visualization;

import android.view.MotionEvent;
import org.ros.math.RosMath;

public class RotateGestureDetector {

  public interface OnRotateGestureListener {
    boolean onRotate(MotionEvent event1, MotionEvent event2, double deltaAngle);
  }

  private static final double MAX_DELTA_ANGLE = 1e-1;

  private final OnRotateGestureListener listener;

  private MotionEvent previousMotionEvent;

  public RotateGestureDetector(OnRotateGestureListener listener) {
    this.listener = listener;
  }

  private double angle(MotionEvent event) {
    double deltaX = (event.getX(0) - event.getX(1));
    double deltaY = (event.getY(0) - event.getY(1));
    return Math.atan2(deltaY, deltaX);
  }

  public boolean onTouchEvent(MotionEvent event) {
    if (event.getPointerCount() != 2) {
      return false;
    }
    if (previousMotionEvent == null) {
      previousMotionEvent = MotionEvent.obtain(event);
      return false;
    }
    double deltaAngle =
        RosMath.clamp(angle(previousMotionEvent) - angle(event), -MAX_DELTA_ANGLE, MAX_DELTA_ANGLE);
    boolean result = listener.onRotate(previousMotionEvent, event, deltaAngle);
    previousMotionEvent.recycle();
    previousMotionEvent = MotionEvent.obtain(event);
    return result;
  }
}