26-拖拉功能和多点触摸

 

main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
<ImageView  
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:src="@drawable/liming"
    android:scaleType="matrix"  <span style="color:#FF0000;">采用矩阵来完成拖拉</span>
    android:id="@+id/imageView"
    />
</LinearLayout>

MainActivity

package cn.itcast.drag;

import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
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 {
    private ImageView imageView;
    
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        
        imageView = (ImageView) this.findViewById(R.id.imageView);
        //图片设置监听器
        imageView.setOnTouchListener(new TouchListener());
    }
    
    private final class TouchListener implements OnTouchListener{
    	private PointF startPoint = new PointF();
    	private Matrix matrix = new Matrix();
    	private Matrix currentMatrix = new Matrix();
    	private int mode = 0;
    	private static final int DRAG = 1;
    	private static final int ZOOM = 2;
    	private float startDis;//开始距离
    	private PointF midPoint;//中间点
    	
		public boolean onTouch(View v, MotionEvent event) {
			//MotionEvent.ACTION_MASK 255 与运算只要最后8位  低8为存储触摸事件
			switch (event.getAction() & MotionEvent.ACTION_MASK) {
			case MotionEvent.ACTION_DOWN://手指压下屏幕
				mode = DRAG;
				currentMatrix.set(imageView.getImageMatrix());//记录ImageView当前的移动位置
				startPoint.set(event.getX(), event.getY());//记录坐标
				break;

			case MotionEvent.ACTION_MOVE://手指在屏幕移动，该 事件会不断地触发
				if(mode == DRAG){
					float dx = event.getX() - startPoint.x;//得到在x轴的移动距离
					float dy = event.getY() - startPoint.y;//得到在y轴的移动距离
					matrix.set(currentMatrix);//在没有进行移动之前的位置基础上进行移动
					matrix.postTranslate(dx, dy);
				}else if(mode == ZOOM){//缩放
					float endDis = distance(event);//结束距离
					if(endDis > 10f){
						float scale = endDis / startDis;//得到缩放倍数
						matrix.set(currentMatrix);
						matrix.postScale(scale, scale, midPoint.x, midPoint.y);
					}
				}				
				break;
				
			case MotionEvent.ACTION_UP://手指离开屏
			case MotionEvent.ACTION_POINTER_UP://有手指离开屏幕,但屏幕还有触点（手指）
				mode = 0;
				break;
				
			case MotionEvent.ACTION_POINTER_DOWN://当屏幕上还有触点（手指），再有一个手指压下屏幕
				mode = ZOOM;
				startDis = distance(event);
				if(startDis > 10f){
					midPoint = mid(event);
					currentMatrix.set(imageView.getImageMatrix());//记录ImageView当前的缩放倍数
				}
				break;
			}
			imageView.setImageMatrix(matrix);//移动图片
			return true;
		}
    	
    }
    /**
     * 计算两点之间的距离
     * @param event
     * @return
     */
	public static float distance(MotionEvent event) {
		float dx = event.getX(1) - event.getX(0);
		float dy = event.getY(1) - event.getY(0);
		return FloatMath.sqrt(dx*dx + dy*dy);
	}
	/**
	 * 计算两点之间的中间点
	 * @param event
	 * @return
	 */
	public static 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);
	}
}