安卓缩放View

public class ScaleLayout extends RelativeLayout implements View.OnTouchListener {
    private boolean isCanTouch = false;
    /**
     * 当前触摸的点数
     */
    private int pointNum = 0;
    //最大的缩放比例
    public static final float SCALE_MAX = 8.0f;
    private static final float SCALE_MIN = 1.0f;

    private double oldDist = 0;
    private double moveDist = 0;
    private double downX = 0;
    private double downY = 0;


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

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

    public ScaleLayout(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        setOnTouchListener(this);
        init();
    }

    private void init() {
        setIsCanTouch(true);
    }

    public void setIsCanTouch(boolean canTouch) {
        isCanTouch = canTouch;
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
        if (!isCanTouch) {
            return false;
        }
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
            case MotionEvent.ACTION_DOWN:
                pointNum = 1;
                downX = event.getX();
                downY = event.getY();
                break;
            case MotionEvent.ACTION_UP:
                pointNum = 0;
                downX = 0;
                downY = 0;
                break;
            case MotionEvent.ACTION_MOVE:
                if (pointNum == 1) {
                    //只有一个手指的时候才有移动的操作
                    float lessX = (float) (downX - event.getX());
                    float lessY = (float) (downY - event.getY());
                    setSelfPivot(lessX, lessY);
                } else if (pointNum == 2) {
                    //只有2个手指的时候才有放大缩小的操作
                    moveDist = spacing(event);
                    double space = moveDist - oldDist;
                    float scale = (float) (getScaleX() + space / getWidth());
                    if (scale > SCALE_MIN && scale < SCALE_MAX) {
                        setScale(scale);
                    } else if (scale < SCALE_MIN) {
                        setScale(SCALE_MIN);
                    }
                }
                break;
            case MotionEvent.ACTION_POINTER_DOWN:
                //两点按下时的距离
                oldDist = spacing(event);
                pointNum += 1;
                break;
            case MotionEvent.ACTION_POINTER_UP:
                pointNum -= 1;
                break;
            default:
                break;
        }
        return true;
    }

    /**
     * 触摸使用的移动事件
     * @param lessX x坐标
     * @param lessY y坐标
     */
    private void setSelfPivot(float lessX, float lessY) {
        float setPivotX ;
        float setPivotY ;
        setPivotX = getPivotX() + lessX;
        setPivotY = getPivotY() + lessY;
        if (setPivotX < 0 && setPivotY < 0) {
            setPivotX = 0;
            setPivotY = 0;
        } else if (setPivotX > 0 && setPivotY < 0) {
            setPivotY = 0;
            if (setPivotX > getWidth()) {
                setPivotX = getWidth();
            }
        } else if (setPivotX < 0 && setPivotY > 0) {
            setPivotX = 0;
            if (setPivotY > getHeight()) {
                setPivotY = getHeight();
            }
        } else {
            if (setPivotX > getWidth()) {
                setPivotX = getWidth();
            }
            if (setPivotY > getHeight()) {
                setPivotY = getHeight();
            }
        }
        setPivot(setPivotX, setPivotY);
    }

    /**
     * 计算两个点的距离
     *
     * @param event 事件
     * @return 返回数值
     */
    private double spacing(MotionEvent event) {
        if (event.getPointerCount() == 2) {
            float x = event.getX(0) - event.getX(1);
            float y = event.getY(0) - event.getY(1);
            return Math.sqrt(x * x + y * y);
        } else {
            return 0;
        }
    }

    /**
     * 平移画面，当画面的宽或高大于屏幕宽高时，调用此方法进行平移
     * @param x 坐标x
     * @param y 坐标y
     */
    public void setPivot(float x, float y) {
        setPivotX(x);
        setPivotY(y);
    }

    /**
     * 设置放大缩小
     * @param scale 缩放值
     */
    public void setScale(float scale) {
        setScaleX(scale);
        setScaleY(scale);
        if (mScaleClick!=null) {
            mScaleClick.onXy(scale,scale);
        }
    }

    /**
     * 初始化比例，也就是原始比例
     */
    public void setInitScale() {
        setScaleX(1.0f);
        setScaleY(1.0f);
        setPivot(getWidth() / 2f, getHeight() / 2f);
    }

    /**
     * 缩放比例监听接口
     */
   public interface  ScaleClick{
        void onXy(float scaMax,float scaMin);
    }
    private ScaleClick mScaleClick;
    public void setOnScaClick(ScaleClick scaleClick){
        mScaleClick = scaleClick;
    }
}