Android View的缩放(sample code)

View缩放。根据两指连线的中点为缩放中心进行缩放。

SacleGesture.java

 1 
 2 
 3 import android.view.ScaleGestureDetector;
 4 import android.view.View;
 5 import android.view.ScaleGestureDetector.OnScaleGestureListener;
 6 import android.view.animation.Animation;
 7 import android.view.animation.ScaleAnimation;
 8 
 9 /**
10  * scale gesture helper.</br>
11  * please invoke {@link ScaleGesture#setSourceView(View)} before dispatch touch event.</br>
12  * if {@link ScaleGesture#setFillAfter(boolean)} parameter is true that keeping same scale when next scaling.</br> 
13  * sample code:
14  * <pre>
15  * ScaleGesture sg = new ScaleGesture();
16  * ScaleGestureDetector detector = new ScaleGestureDetector(getContext(), sg);
17  * ...
18  * sg.setSourceView(...);
19  * ... 
20  * onTouchEvent(MotionEvent) {
21  *     ...
22  *     detector.onTouchEvent(event);
23  *     ...
24  * }
25  * </pre>
26  * 
27  * @author bin
28  *
29  */
30 public class ScaleGesture implements OnScaleGestureListener {
31     
32     private float beforeFactor;
33     private float mPivotX;
34     private float mPivotY;
35     private View mVSouce;
36     private boolean isFillAfter;
37     
38     public void setSourceView(View destinyView) {
39         mVSouce = destinyView;
40     }
41     
42     @Override
43     public boolean onScale(ScaleGestureDetector detector) {
44         if (checkIsNull()) {
45             return false;
46         }
47         final float factor = detector.getScaleFactor();
48         Animation animation = new ScaleAnimation(beforeFactor, factor, 
49                 beforeFactor, factor, mPivotX , mPivotY);
50         animation.setFillAfter(true);
51         mVSouce.startAnimation(animation);
52         beforeFactor = factor;
53         return false;
54     }
55     
56     @Override
57     public boolean onScaleBegin(ScaleGestureDetector detector) {
58         if (checkIsNull()) {
59             return false;
60         }
61         beforeFactor = 1f;
62         mPivotX = detector.getFocusX() - mVSouce.getLeft();
63         mPivotY = mVSouce.getTop() + (mVSouce.getHeight() >> 1);
64         return true;
65     }
66     
67     @Override
68     public void onScaleEnd(ScaleGestureDetector detector) {
69         if (checkIsNull()) {
70             return;
71         }
72         final float factor = detector.getScaleFactor();
73         final int nWidth = (int) (mVSouce.getWidth() * factor);
74         final int nHeight = (int) mVSouce.getHeight();
75         final int nLeft = (int) (mVSouce.getLeft() - ((nWidth - mVSouce.getWidth()) * 
76                 (mPivotX / mVSouce.getWidth())));
77         final int nTop = (int) mVSouce.getTop();
78         if (isFillAfter) {
79             mVSouce.layout(nLeft, nTop, nLeft + nWidth, nTop + nHeight);                
80         }
81         // MUST BE CLEAR ANIMATION. OTHERWISE WILL BE FLICKER
82         mVSouce.clearAnimation();
83     }
84     
85     public boolean checkIsNull() {
86         return mVSouce == null ? true : false;
87     }
88     
89     /**
90      * if parameter is true that keeping same scale when next scaling.
91      * @param isFill
92      */
93     public void setFillAfter(boolean isFill) {
94         isFillAfter = isFill;
95     }
96 }

 

posted @ 2013-03-13 11:01  wFeng  阅读(3269)  评论(0)  编辑  收藏  举报