android图片缩放、放大demo - Android实例教程

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

来自为知笔记(Wiz)