多点触控（缩放图片）

 

 

准备一张名为picture的图片。

 

 

 

布局文件main.xml不用编写

 

 

 

 

 

 

在MyMultitouchDemo.java中：

 

package com.li.multitouch;

 

import android.app.Activity;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Canvas;

import android.graphics.Matrix;

import android.graphics.Paint;

import android.os.Bundle;

import android.view.MotionEvent;

import android.view.SurfaceHolder;

import android.view.SurfaceView;

import android.view.Window;

import android.widget.ImageView;

 

public class MyMultitouchDemo extends Activity {

  private static final int SCALEBASIC = 3 ;// 调整的比率

  private int imageX = 0 ;  // 计算图片的X轴

  private int imageY = 0 ;  // 计算图片的Y轴

  private SurfaceHolder holder = null ;

  private int screenWidth = 0 ; //屏幕宽度

  private int screenHeight = 0 ; //屏幕高度

  private int imageWidth = 0 ;  //图片宽度

  private int imageHeight = 0 ; //图片高度

  private Bitmap bitmap = null ;

  @Override

  public void onCreate(Bundle savedInstanceState) {

     super.onCreate(savedInstanceState);

     super.requestWindowFeature(Window.FEATURE_NO_TITLE) ;

     this.screenWidth = super.getWindowManager()

         .getDefaultDisplay().getWidth() ;  //获得屏幕的宽度

     this.screenHeight = super.getWindowManager()

         .getDefaultDisplay().getHeight() ; //获得屏幕的高度

     this.bitmap = BitmapFactory.decodeResource(super.getResources(),

         R.drawable.picture);

     this.imageWidth = this.bitmap.getWidth() ;  //获得图片的宽度

     this.imageHeight = this.bitmap.getHeight() ; //获得图片的高度

     this.imageX = (this.screenWidth - this.imageWidth) / 2 ;

     this.imageY = (this.screenHeight - this.imageHeight) / 2 ;

     super.setContentView(new MySurfaceView(this));

  }

 

  private class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback {

    

     public MySurfaceView(Context context) {

       super(context);

       MyMultitouchDemo.this.holder = super.getHolder() ;

       MyMultitouchDemo.this.holder.addCallback(this) ;

       super.setFocusable(true) ;  // 获得焦点，进行触摸事件

     }

 

     public void surfaceChanged(SurfaceHolder holder, int format, int width,

         int height) {

      

     }

 

     public void surfaceCreated(SurfaceHolder holder) {

       MyMultitouchDemo.this.setImage(1.0f, 300, 450);

     }

 

     public void surfaceDestroyed(SurfaceHolder holder) {

      

     }

  }

 

  private void setImage(float scale, int width, int height) {  // 改变之后修改图片

     Canvas canvas = MyMultitouchDemo.this.holder.lockCanvas() ;  // 获取画布

     Paint paint = new Paint() ;

     canvas.drawRect(0, 0, MyMultitouchDemo.this.screenWidth,

         MyMultitouchDemo.this.screenHeight, paint); //画底色消除从影

     Matrix matrix = new Matrix() ;

     matrix.postScale(scale, scale) ; // 等量缩放

     Bitmap target = Bitmap.createBitmap(MyMultitouchDemo.this.bitmap, 0, 0,

         width, height, matrix, true);

     this.imageWidth = target.getWidth() ;

     this.imageHeight = target.getHeight() ;

     this.imageX = (this.screenWidth - this.imageWidth) / 2 ;

     this.imageY = (this.screenHeight - this.imageHeight) / 2 ;

     canvas.translate(this.imageX, this.imageY) ; // 平移到指定的位置

     canvas.drawBitmap(this.bitmap, matrix, paint) ;

    MyMultitouchDemo.this.holder.unlockCanvasAndPost(canvas) ;// 解锁，并提交图象

  }

 

  @Override

  public boolean onTouchEvent(MotionEvent event) {

     int pointCount = event.getPointerCount() ;

     if (pointCount == 2) {

       float pointA = event.getY(0) ;

       float pointB = event.getY(1) ;

       if(pointA < pointB) {

         float temp = pointA ;

         pointA = pointB ;

         pointB = temp ;

       }

       if(!(event.getAction() == MotionEvent.ACTION_UP)) {

         float scale = this.getScale(pointA, pointB) / SCALEBASIC;

         MyMultitouchDemo.this.setImage(scale, 300,450) ;

       }

     }

     return super.onTouchEvent(event);

  }

  private float getScale(float pointA,float pointB) {

     float scale = pointA / pointB ;

     return scale ;

  }

}