多点触控

package com.example.tupian_moxing;

import android.os.Bundle;

import android.app.Activity;

import android.util.FloatMath;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnTouchListener;

import android.widget.ImageView;

import android.graphics.Matrix;

import android.graphics.PointF;

public class MainActivity extends Activity {

private ImageView img;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

img=(ImageView)this.findViewById(R.id.img);

img.setOnTouchListener(new OnTouchListener() {

/** 记录是拖拉照片模式还是放大缩小照片模式 */

private int mode = 0;// 初始状态

/** 拖拉照片模式 */

private static final int MODE_DRAG = 1;

/** 放大缩小照片模式 */

private static final int MODE_ZOOM = 2;

/** 用于记录开始时候的坐标位置 */

private PointF startPoint = new PointF();

/** 用于记录拖拉图片移动的坐标位置 */

private Matrix oldmatrix = new Matrix();

/** 用于记录图片要进行拖拉时候的坐标位置 */

private Matrix newMatrix = new Matrix();

/** 两个手指的开始距离 */

private float startDis;

/** 两个手指的中间点 */

private PointF midPoint;

@Override

public boolean onTouch(View arg0, MotionEvent arg1) {

// TODO Auto-generated method stub

switch (arg1.getAction()&MotionEvent.ACTION_MASK) {

case MotionEvent.ACTION_DOWN:

mode = MODE_DRAG;

oldmatrix.set(img.getImageMatrix());

startPoint.set(arg1.getX(),arg1.getY());

break;

case MotionEvent.ACTION_MOVE:

if(mode==MODE_DRAG){

float dx=arg1.getX()-startPoint.x;

float dy=arg1.getY()-startPoint.y;

newMatrix.set(oldmatrix);

newMatrix.postTranslate(dx, dy);

}else if(mode==MODE_ZOOM){

float end=distance(arg1);

if(end>10f){

float scale=end/startDis;

newMatrix.set(oldmatrix);

newMatrix.postScale(scale,scale,midPoint.x,midPoint.y);

}

}

break;

case MotionEvent.ACTION_UP:

case MotionEvent.ACTION_POINTER_UP:

mode=0;

break;

case MotionEvent.ACTION_POINTER_DOWN:

mode=MODE_ZOOM;

startDis=distance(arg1);

if (startDis > 10f) { // 两个手指并拢在一起的时候像素大于10

midPoint = mid(arg1);

//记录当前ImageView的缩放倍数

oldmatrix.set(img.getImageMatrix());

}

break;

}

img.setImageMatrix(newMatrix);

return true;

}

/** 计算两个手指间的距离 */

private float distance(MotionEvent event) {

float dx = event.getX(1) - event.getX(0);

float dy = event.getY(1) - event.getY(0);

/** 使用勾股定理返回两点之间的距离 */

return FloatMath.sqrt(dx * dx + dy * dy);

}

/** 计算两个手指间的中间点 */

private PointF mid(MotionEvent event) {

float midX = (event.getX(1)+event.getX(0))/2;

float midY = (event.getY(1)+event.getY(0))/2;

return new PointF(midX, midY);

}

});

}

}

//布局文件

<ImageView

android:scaleType="matrix"

android:id="@+id/img"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:src="@drawable/haha"

/>