手指多点触控事件

package com.itheima.touch;

import android.app.Activity;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.os.Bundle;
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
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        imageView = (ImageView) findViewById(R.id.imageView);
        imageView.setOnTouchListener(new MyOnTouchListener());        // 添加触摸监听器
    }
    
    private class MyOnTouchListener implements OnTouchListener {
        private float x;        // 图片移动前的x轴坐标
        private float y;        // 图片移动前的y轴坐标
        private Matrix newMatrix = new Matrix();         // 用来移动图片的矩阵
        private Matrix oldMatrix = new Matrix();        // 图片移动前的矩阵
        private int type;        // 操作类型, 一根手指触摸还是两根手指触摸
        private float start;    // 第二根手指按下时的距离
        private float end;        // 两根手指移动后的距离
        private PointF point;    // 放大时的中心点

        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction() & MotionEvent.ACTION_MASK) {  
                case MotionEvent.ACTION_DOWN:
                    type = 1;
                    x = event.getX();
                    y = event.getY();
                    oldMatrix.set(imageView.getImageMatrix());
                    break;
                case MotionEvent.ACTION_POINTER_DOWN:
                    type = 2;
                    start = countDistance(event);         // 计算第二根手指按下时两点之间的距离
                    point = countPoint(event);             // 计算中心点
                    oldMatrix.set(imageView.getImageMatrix());
                    break;
                case MotionEvent.ACTION_MOVE:
                    newMatrix.set(oldMatrix);
                    if (type == 1) {     // 1根手指触摸
                        newMatrix.postTranslate(event.getX() - x, event.getY() - y);
                    } else {             // 2跟手指触摸
                        end = countDistance(event);     // 计算结束时距离
                        float scale = end / start;         // 计算缩放比例
                        newMatrix.postScale(scale, scale, point.x, point.y);     // 对模型进行缩放
                    }
                    break;
            }
            imageView.setImageMatrix(newMatrix);     // 改变图片
            return true;
        }
    }

    public float countDistance(MotionEvent event) {
        float a = event.getX(1) - event.getX(0);     // x轴距离
        float b = event.getY(1) - event.getY(0);     // y轴距离
        return (float) Math.sqrt(a * a + b * b);     // 勾股定理
    }

    public PointF countPoint(MotionEvent event) {
        float x = (event.getX(0) + event.getX(1)) / 2;     // x轴中间点
        float y = (event.getY(0) + event.getY(1)) / 2;     // y轴中间点
        return new PointF(x, y);
    }

    
    /*
    private class MyOnTouchListener implements OnTouchListener {
        private float x;
        private float y;
        private Matrix oldMatrix = new Matrix();
        private Matrix newMatrix = new Matrix();        // 用来操作图片的模型

        public boolean onTouch(View v, MotionEvent event) {
            switch (event.getAction()) {                // 判断触摸动作的类型
                case MotionEvent.ACTION_DOWN:             // 按下时
                    x = event.getX();                     // 获取x轴坐标
                    y = event.getY();                    // 获取y轴坐标
                    oldMatrix.set(imageView.getImageMatrix());        // 用模型记住图片所在位置
                    break;
                case MotionEvent.ACTION_MOVE:             // 移动时
                    newMatrix.set(oldMatrix);             // 用另一个模型记住按下时的位置
                    newMatrix.postTranslate(event.getX() - x, event.getY() - y);    // 移动模型
                    break;
            }
            imageView.setImageMatrix(newMatrix);        // 把图片放到了移动后的模型中
            return true;
        }
    }
    */
    
}