注：一定要通過view的onTouchEvent調用mScaleGestureDetector.onTouchEvent(ev);，只有這樣

才能調用回調函數：onScaleBegin

具體可以參加：android源碼：KenBurnsActivity.java

下面是轉載的文章：

Detects transformation gestures involving more than one pointer ("multitouch") using the supplied?MotionEvents.

?TheScaleGestureDetector.OnScaleGestureListener?callback will notify users when a particular gesture event has occurred. This class should only be used with?MotionEvents reported via touch. To use this class:

• Create an instance of the?ScaleGestureDetector?for your?View
• In the?(View's )onTouchEvent(MotionEvent)?method ensure you call?(ScaleGestureDetector's )onTouchEvent(MotionEvent). The methods defined in your callback will be executed when the events occur.

下面是測試的代碼：

public?class?TouchView?extends?View?{

?private?Context?mContext;

?private?Paint?mPaint;

?private?Rect mRect;

?private?ScaleGestureDetector mScaleGestureDetector;

?

?public?TouchView(Context?context)?{

??super(context);

??mContext?=?context;

??mPaint?=?new?Paint();

??mPaint.setColor(Color.BLUE);

??mPaint.setFlags(Paint.ANTI_ALIAS_FLAG);

??mRect?=?new?Rect();

??mRect.left?=?10;

??mRect.top?=?10;

??mRect.right?=?300;

??mRect.bottom?=?400;

??

??mScaleGestureDetector?=?new?ScaleGestureDetector(context,?listener);

?}

?

?OnScaleGestureListener listener?=?new?OnScaleGestureListener()?{

??

??public?void?onScaleEnd(ScaleGestureDetector?detector)?{

???// TODO Auto-generated method stub

???Log.i("OnScaleGestureListener",?"onScaleEnd");

??}

??

??public?boolean?onScaleBegin(ScaleGestureDetector?detector)?{

???// TODO Auto-generated method stub

???Log.i("OnScaleGestureListener",?"onScaleBegin?detector.getCurrentSpan() = "?+?detector.getCurrentSpan());

???detector.getCurrentSpan();

???return?true;

??}

??

??public?boolean?onScale(ScaleGestureDetector?detector)?{

???// TODO Auto-generated method stub

???float?cur?=?detector.getCurrentSpan();

???float?pre?=?detector.getPreviousSpan();

???float?cp?=?cur?-?pre;

???Log.i("OnScaleGestureListener",?"onScale?detector.getCurrentSpan() = "?+?cur

?????+?"?detector.getPreviousSpan() = "?+?pre?

?????+?" cur - pre = "?+?(cur?-?pre));

???if?(cp?<?-100?&&?!mScaled)?{

????mScaled?=?true;

????mRect.left?=?10+?50;

????mRect.top?=?10?+?50;

????mRect.right?=?300?-?50;

????mRect.bottom?=?400?-?50;

????invalidate();

???}?else?if?(cp?>?100?&&?mScaled)?{

????mScaled?=?false;

????mRect.left?=?10;

????mRect.top?=?10?;

????mRect.right?=?300?;

????mRect.bottom?=?400;

????invalidate();

???}

???return?false;

??}

?};

?boolean?mScaled?=?false;

?/*@Override

?protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {

??int widthMode = MeasureSpec.getMode(widthMeasureSpec);

??int width = MeasureSpec.getSize(widthMeasureSpec);

??int heightMode = MeasureSpec.getMode(heightMeasureSpec);

??int height = MeasureSpec.getSize(heightMeasureSpec);

??super.onMeasure(widthMeasureSpec, heightMeasureSpec);

?}*/

?@Override

?protected?void?onDraw(Canvas?canvas)?{

??canvas.drawRect(mRect,?mPaint);

?}

?@Override

?public?boolean?onTouchEvent(MotionEvent?event)?{

??System.out.println("event.getPointerCount() : "?+?event.getPointerCount());

??mScaleGestureDetector.onTouchEvent(event);

??return?true;

?}

}

轉載于:https://www.cnblogs.com/tanqiantot/archive/2012/10/12/3126845.html

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