学步园

Android多点触控在本质上需要LCD驱动和程序本身设计上支持，目前市面上只要使用电容屏触控原理的手机均可以支持多点触控Multitouch技术，对于网页缩放、手势操作上有更好的用户体验。 在Android平台上事件均使用了MotionEvent对象方式处理，比如开始触控时会触发ACTION_DOWN而移动操作时为 ACTION_MOVE最终放开手指时触发ACTION_UP事件。当然还有用户无规则的操作可能触发ACTION_CANCEL这个动作.

对于常规的控件触控操作在内部为View的setOnTouchListener()接口实现的 onTouchEvent()方法来处理。

下面用ImageView做演示：

main.xml:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >
<ImageView android:id="@+id/imageView"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:src="@drawable/pic"
android:scaleType="matrix" >
</ImageView>
</FrameLayout>

要注意的是 android:scaleType 的属性必须设置为matrix，否则图片无法改变大小。

java文件：

package com.shao.muti;

import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
import android.util.Log;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.widget.ImageView;

public class MutiTouchActivity extends Activity implements OnTouchListener{
    /** Called when the activity is first created. */
    private static final String TAG="Touch";
    private static final int NONE= 0 ;
    private static final int DRAG = 1;
    private static final int ZOOM =2;
    int mode  = NONE;
    Matrix matrix = new Matrix();
    Matrix savedMatrix =  new Matrix();
    
    PointF start = new PointF();
    PointF mid = new PointF();
    float oldDist = 1f;
    
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ImageView view = (ImageView) findViewById(R.id.imageView);
        view.setOnTouchListener(this);
	}

	@Override
	public boolean onTouch(View v, MotionEvent event) {
		// TODO Auto-generated method stub
		ImageView view = (ImageView) v;
		printEventinfo(event);//测试输出信息
		switch(event.getAction()&MotionEvent.ACTION_MASK)
		{
		case MotionEvent.ACTION_DOWN:
			savedMatrix.set(matrix);
			   //設置初始點位置
			start.set(event.getX(),event.getY());
			Log.d(TAG,"mode=DRAG");
			mode  =DRAG;
			break;
		case MotionEvent.ACTION_POINTER_1_DOWN:
			oldDist= spacing(event);
			Log.d(TAG,"lodDist="+oldDist);
			if(oldDist>10f){
				savedMatrix.set(matrix);
				midPoint(mid,event);
				mode = ZOOM;
				Log.d(TAG,"mode=ZOOM");
				
			}
			break;
		case MotionEvent.ACTION_UP:
		case MotionEvent.ACTION_POINTER_1_UP:
			mode  =NONE;
			Log.d(TAG,"mode=NONE");
			break;
		case MotionEvent.ACTION_MOVE:
			if(mode==DRAG){
				matrix.set(savedMatrix);
				matrix.postTranslate(event.getX()-start.x, event.getY()-start.y);
			}
			else if(mode == ZOOM){
				 float newDist = spacing(event);
		            Log.d(TAG, "newDist=" + newDist);
		            if (newDist > 10f) {
		               matrix.set(savedMatrix);
		               float scale = newDist / oldDist;
		               matrix.postScale(scale, scale, mid.x, mid.y);
		            }
		         }
			break;
		}
		view.setImageMatrix(matrix);
		return true;
		
	}
	private void printEventinfo(MotionEvent event){
		int num =0;
		System.out.println("触控动作---->"+event.getAction()); //获取触控动作比如ACTION_DOWN
		System.out.println("取触控点的数量--->"+event.getPointerCount()); //获取触控点的数量，比如2则可能是两个手指同时按压屏幕
		num = event.getPointerCount();
		for(int i=0;i<num;i++){
			System.out.println("索引-->"+event.getPointerId(i)); //对于每个触控的点的细节，我们可以通过一个循环执行getPointerId方法获取索引
			System.out.println("第i个触控点的x位置-->"+event.getX(i)); //获取第i个触控点的x位置
			System.out.println("第i个触控点的y位置-->"+event.getY(i)); //获取第i个点触控的y位置
			System.out.println("手指压力-->"+event.getPressure(i)); //LCD可以感应出用户的手指压力，当然具体的级别由驱动和物理硬件决定的
		}
		System.out.println("开始时间"+event.getDownTime()); //按下开始时间
		System.out.println(" 事件结束时间"+event.getEventTime()); // 事件结束时间
		System.out.println("总共按下时花费时间"+(event.getEventTime()-event.getDownTime())); //总共按下时花费时间

	}
	  /** Determine the space between the first two fingers */
	private float spacing(MotionEvent event){
		float x = event.getX(0)-event.getY(1);
		float y = event.getY(0)-event.getY(1);
		return (float)Math.sqrt(x*x+y*y);
	}
	/** Calculate the mid point of the first two fingers */
	   private void midPoint(PointF point, MotionEvent event) {
	      float x = event.getX(0) + event.getX(1);
	      float y = event.getY(0) + event.getY(1);
	      point.set(x / 2, y / 2);
	   }
}