示例
原图：
拖动查看其他部分：
放大仔细查看
代码示例，注释比较详细，其他不多讲了
package com.study.drascale;
import android.os.Bundle;
import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;
public class MainActivity extends Activity {
ImageView imageView;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
imageView = (ImageView) findViewById(R.id.img);
imageView.setOnTouchListener(new TounchListener());
}
private class TounchListener implements OnTouchListener{
private PointF startPoint = new PointF();
private Matrix matrix = new Matrix();
private Matrix currentMaritx = new Matrix();
private int mode = 0;//用于标记模式
private static final int DRAG = 1;//拖动
private static final int ZOOM = 2;//放大
private float startDis = 0;
private PointF midPoint;//中心点
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
mode = DRAG;
currentMaritx.set(imageView.getImageMatrix());//记录ImageView当期的移动位置
startPoint.set(event.getX(),event.getY());//开始点
break;
case MotionEvent.ACTION_MOVE://移动事件
if (mode == DRAG) {//图片拖动事件
float dx = event.getX() - startPoint.x;//x轴移动距离
float dy = event.getY() - startPoint.y;
matrix.set(currentMaritx);//在当前的位置基础上移动
matrix.postTranslate(dx, dy);
} else if(mode == ZOOM){//图片放大事件
float endDis = distance(event);//结束距离
if(endDis > 10f){
float scale = endDis / startDis;//放大倍数
matrix.set(currentMaritx);
matrix.postScale(scale, scale, midPoint.x, midPoint.y);
}
}
break;
case MotionEvent.ACTION_UP:
mode = 0;
break;
//有手指离开屏幕，但屏幕还有触点(手指)
case MotionEvent.ACTION_POINTER_UP:
mode = 0;
break;
//当屏幕上已经有触点（手指）,再有一个手指压下屏幕
case MotionEvent.ACTION_POINTER_DOWN:
mode = ZOOM;
startDis = distance(event);
if(startDis > 10f){//避免手指上有两个茧
midPoint = mid(event);
currentMaritx.set(imageView.getImageMatrix());//记录当前的缩放倍数
}
break;
}
imageView.setImageMatrix(matrix);
return true;
}
}
/**
* 两点之间的距离
* @param event
* @return
*/
private static float distance(MotionEvent event){
//两根线的距离
float dx = event.getX(1) - event.getX(0);
float dy = event.getY(1) - event.getY(0);
return FloatMath.sqrt(dx*dx + dy*dy);
}
/**
* 计算两点之间中心点的距离
* @param event
* @return
*/
private static PointF mid(MotionEvent event){
float midx = event.getX(1) + event.getX(0);
float midy = event.getY(1) - event.getY(0);
return new PointF(midx/2, midy/2);
}
}
示例下载：
http://download.csdn.net/detail/sdefzhpk/4542576