Android Open Source - android-open-street-map Scale Gesture Pre Froyo Helper

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License

The source code is released under:

Apache License

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Java Source Code

package com.android.lib.map.osm.helpers;
// www  .  j  a v  a 2  s . c o m
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.FloatMath;
import android.view.MotionEvent;


public class ScaleGesturePreFroyoHelper {

  public final static int DRAG = 2;
  public final static int ZOOM = 1;
  public final static int NONE = 0;
  public int mMode = NONE;
  private float mOldDist = 1f;
  private final PointF start = new PointF();
  private final Matrix matrix = new Matrix();
  private final Matrix savedMatrix = new Matrix();
  private IScaleGesturePreFroyo mScaleGesture;
  private float mLastZoomDist;
  
  public final PointF mMid = new PointF();
  
  public ScaleGesturePreFroyoHelper(IScaleGesturePreFroyo scaleGesture) {
    mScaleGesture = scaleGesture;
  }
  
  private float spacing(MotionEvent event) {
    float x = event.getX(0) - event.getX(1);
    float y = event.getY(0) - event.getY(1);
    return FloatMath.sqrt(x * x + y * y);
  }

  private void midPoint(PointF point, MotionEvent event) {
    if (event.getPointerCount() >= 2) {
      float x = event.getX(0) + event.getX(1);
      float y = event.getY(0) + event.getY(1);
      point.set(x / 2, y / 2);
    }
  }

  public boolean onTouchEvent(final MotionEvent event) {

    try {
    
      switch (event.getAction() & MotionEvent.ACTION_MASK) {
      case MotionEvent.ACTION_DOWN:
        savedMatrix.set(matrix);
        start.set(event.getX(), event.getY());
        mMode = DRAG;
        break;
      case MotionEvent.ACTION_POINTER_DOWN:
        mOldDist = spacing(event);
        if (mOldDist > 10f) {
          savedMatrix.set(matrix);
          midPoint(mMid, event);
          mMode = ZOOM;
          mScaleGesture.onScaleBegin(event);
        }
        break;
      case MotionEvent.ACTION_UP:
        if (mMode == ZOOM) {
          mMode = NONE;
          return true;
        }
        mMode = NONE;
        break;
      case MotionEvent.ACTION_POINTER_UP:
        if (mMode == ZOOM) {
          mScaleGesture.onScaleEnd(mOldDist, mLastZoomDist);
          return true;
        }
        break;
      case MotionEvent.ACTION_MOVE:
        if (mMode == DRAG) {
          // ...
          matrix.set(savedMatrix);
          matrix.postTranslate(event.getX() - start.x, event.getY()
              - start.y);
        } else if (mMode == ZOOM) {
          
          float newDist = spacing(event);
          mScaleGesture.onScale(event, mOldDist, newDist);
          mLastZoomDist = newDist;
          
          if (newDist > 10f) {
            matrix.set(savedMatrix);
            float scale = newDist / mOldDist;
            matrix.postScale(scale, scale, mMid.x, mMid.y);
          }
          return true;
        }
        break;
      }
      
    } catch (IllegalArgumentException iae) {
      
    } catch (Exception e) {
      e.printStackTrace();
    }
      
    return false;
  }

  public interface IScaleGesturePreFroyo {
    public void onScaleBegin(MotionEvent event);
    public void onScale(MotionEvent event, float startDistance, float lastDistance);
    public void onScaleEnd(float startDistance, float lastDistance);
  }
}

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