android view 实现双指平移、缩放、旋转

ZoomView 是一个可以实现单指平移，双指缩放和旋转的view，内部包含的view也会跟着一起变化，示例继承自RelativeLayout，也可以根据自己需要继承自所有View类的子类。
核心逻辑代码如下所示，需要的同学直接copy下面的代码到工程中就可以直接使用：

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.RelativeLayout;

public class ZoomView extends RelativeLayout {
    // 属性变量
    private float translationX; // 移动X
    private float translationY; // 移动Y
    private float scale = 1; // 伸缩比例
    private float rotation; // 旋转角度

    // 移动过程中临时变量
    private float actionX;
    private float actionY;
    private float spacing;
    private float degree;
    private int moveType; // 0=未选择，1=拖动，2=缩放

    public ZoomView(Context context) {
        this(context, null);
    }

    public ZoomView(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public ZoomView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setClickable(true);
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        getParent().requestDisallowInterceptTouchEvent(true);
        return super.onInterceptTouchEvent(ev);
    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                moveType = 1;
                actionX = event.getRawX();
                actionY = event.getRawY();
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                moveType = 2;
                spacing = getSpacing(event);
                degree = getDegree(event);
                break;
            case MotionEvent.ACTION_MOVE:
                if (moveType == 1) {
                    translationX = translationX + event.getRawX() - actionX;
                    translationY = translationY + event.getRawY() - actionY;
                    setTranslationX(translationX);
                    setTranslationY(translationY);
                    actionX = event.getRawX();
                    actionY = event.getRawY();
                } else if (moveType == 2) {
                    scale = scale * getSpacing(event) / spacing;
                    setScaleX(scale);
                    setScaleY(scale);
                    rotation = rotation + getDegree(event) - degree;
                    if (rotation > 360) {
                        rotation = rotation - 360;
                    }
                    if (rotation < -360) {
                        rotation = rotation + 360;
                    }
                    setRotation(rotation);
                }
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_POINTER_UP:
                moveType = 0;
        }
        return super.onTouchEvent(event);
    }

    // 触碰两点间距离
    private float getSpacing(MotionEvent event) {
        //通过三角函数得到两点间的距离
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(x * x + y * y);
    }

    // 取旋转角度
    private float getDegree(MotionEvent event) {
        //得到两个手指间的旋转角度
        double delta_x = event.getX(0) - event.getX(1);
        double delta_y = event.getY(0) - event.getY(1);
        double radians = Math.atan2(delta_y, delta_x);
        return (float) Math.toDegrees(radians);
    }
}

使用方式如下，是不是非常简单：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.zhangxq.zoomview.ZoomView
        android:id="@+id/zoomView"
        android:layout_width="300dp"
        android:layout_height="300dp"
        android:layout_centerInParent="true">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:src="@drawable/test" />

    </com.zhangxq.zoomview.ZoomView>
</RelativeLayout>