如何在Android中实现多点触控监听与交互优化

在android中多指触控通过OnTouchListener监听器监听，触控事件在onTouch方法中分析处理。

在单指触控中，我们常用的三个方法ACTION_DOWN、ACTION_UP、ACTION_MOVE，在多指触控中也会用到，不过用法稍有不同。

多指触控中多了ACTION_POINTER_DOWN、ACTION_POINTER_UP两种情况，这几个情况的触发用法在下面源码中标注：

switch (event.getAction() &MotionEvent.ACTION_MASK) {case MotionEvent.ACTION_DOWN: //第一根手指按下时触发

mode = 1;break;case MotionEvent.ACTION_POINTER_DOWN: //第二根或以上的手指按下时触发

mode += 1;break;case MotionEvent.ACTION_UP: //所有手指都离开时触发

mode = 0;break;case MotionEvent.ACTION_POINTER_UP: //当有两根及以上手指触碰屏幕，其一离开时触发

mode -= 1;break;case MotionEvent.ACTION_MOVE: //此事件非常灵敏，只要有手指触碰屏幕，便会一直触发

if (mode >= 2) {

}break;

}

触碰的手指数可用event.getPointerCount()方法获取。

放大缩小：

此功能可通过手指之间的前后距离倍数来确定放大缩小的倍数，不这样稍微麻烦了点，我们可以用ScaleGestureDetector来实现：

scaleGestureDetector = new ScaleGestureDetector(this, newScaleGestureDetector.OnScaleGestureListener() {

@Overridepublic booleanonScale(ScaleGestureDetector detector) {float factor =detector.getScaleFactor();float x =detector.getFocusX();float y =detector.getFocusY();

Show.log("onScale:" + factor + ";" + x + ";" +y);

matrix.postScale(factor, factor, x, y);

iv.setImageMatrix(matrix);return true;

}

@Overridepublic booleanonScaleBegin(ScaleGestureDetector detector) {

Show.log("onScaleBegin");return true;

}

@Overridepublic voidonScaleEnd(ScaleGestureDetector detector) {

Show.log("onScaleEnd");

}

});

iv=(ImageView) findViewById(R.id.img_test);

iv.setOnTouchListener(newOnTouchListener() {

@Overridepublic booleanonTouch(View v, MotionEvent event) {\

scaleGestureDetector.onTouchEvent(event);return true;

}

});

多指滑动：

先获取各点的中点，而后根据中点的位移来进行判断，下面是一个简单样例：

public class MainActivity extendsActivity {privateImageView iv;

Matrix matrix= newMatrix();privatePointF startPoint;privatePointF nowPoint;

@Overrideprotected voidonCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

startPoint= newPointF();

nowPoint= newPointF();

iv=(ImageView) findViewById(R.id.img_test);

iv.setOnTouchListener(newOnTouchListener() {

@Overridepublic booleanonTouch(View v, MotionEvent event) {switch (event.getAction() &MotionEvent.ACTION_MASK) {caseMotionEvent.ACTION_DOWN:caseMotionEvent.ACTION_POINTER_DOWN:

setEventPoint(event,startPoint);break;caseMotionEvent.ACTION_MOVE:

setEventPoint(event,nowPoint);

Show.log("move:"+getDistance(startPoint,nowPoint));

matrix.postTranslate(nowPoint.x-startPoint.x,nowPoint.y-startPoint.y);

startPoint.set(nowPoint.x,nowPoint.y);break;caseMotionEvent.ACTION_UP:

setEventPoint(event,nowPoint);

Show.log("end:"+getDistance(startPoint,nowPoint));break;

}

iv.setImageMatrix(matrix);return true;

}

});

}private voidsetEventPoint(MotionEvent event, PointF startPoint) {float x = 0, y = 0;final int pointerCount =event.getPointerCount();for (int i = 0; i

x+=event.getX(i);

y+=event.getY(i);

}

x= x /pointerCount;

y= y /pointerCount;

startPoint.set(x,y);

}private floatgetDistance(PointF point1,PointF point2){float x = point1.x-point2.x;float y = point1.y-point2.y;return (float) Math.sqrt(x * x + y *y);

}

}