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;
}
}
*/

}