请教一个自定义View的问题

Question

自定义拖拽缩放的ImageView,现在这样左上右正常不会拖出屏幕外,但是底部可以拖出屏幕外面.该怎样定义这个高度让它不会被拖出底部?试着拿了屏幕的高度设置上去,或者减去导航栏高度也不行.下面是拖出底部的截图和自定义View的代码

自定义view:

public class DragScaleView extends AppCompatImageView implements View.OnTouchListener {

    protected int screenWidth;
    protected int screenHeight;
    protected static int lastX;
    protected static int lastY;
    private int oriLeft;
    private int oriRight;
    private int oriTop;
    private int oriBottom;
    private int dragDirection;
    private static final int TOP = 0x15;
    private static final int LEFT = 0x16;
    private static final int BOTTOM = 0x17;
    private static final int RIGHT = 0x18;
    private static final int LEFT_TOP = 0x11;
    private static final int RIGHT_TOP = 0x12;
    private static final int LEFT_BOTTOM = 0x13;
    private static final int RIGHT_BOTTOM = 0x14;
    private static final int TOUCH_TWO = 0x21;
    private static final int CENTER = 0x19;
    private int offset = 0; //可超出其父控件的偏移量
    protected Paint paint = new Paint();
    private static final int touchDistance = 80; //触摸边界的有效距离
    private static final String TAG = "DragScaleView";

    // 初始的两个手指按下的触摸点的距离
    private float oriDis = 1f;

    private int mZoomWidth; //缩放后的宽
    private int mZoomHeight; //缩放后的高

    /**
     * 初始化获取屏幕宽高
     */
    protected void initScreenW_H() {
//        screenHeight = getResources().getDisplayMetrics().heightPixels - 40;
        int daoHangHeight = getDaoHangHeight(getContext());//80

        Log.d(TAG, "initScreenW_H: gao="+daoHangHeight);
//        screenHeight = getResources().getDisplayMetrics().heightPixels -daoHangHeight;
        screenHeight = getResources().getDisplayMetrics().heightPixels; //todo:这样设置会拖出底部
        screenWidth = getResources().getDisplayMetrics().widthPixels;
    }

    public static int getDaoHangHeight(Context context) {
        int result = 0;
        int resourceId=0;
        int rid = context.getResources().getIdentifier("config_showNavigationBar", "bool", "android");
        if (rid!=0){
            resourceId = context.getResources().getIdentifier("navigation_bar_height", "dimen", "android");
//            CMLog.show("高度："+resourceId);
//            CMLog.show("高度："+context.getResources().getDimensionPixelSize(resourceId) +"");
            return context.getResources().getDimensionPixelSize(resourceId);
        }else
            return 0;
    }


    public DragScaleView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        setOnTouchListener(this);
        initScreenW_H();
    }

    public DragScaleView(Context context, AttributeSet attrs) {
        super(context, attrs);
        setOnTouchListener(this);
        initScreenW_H();
    }

    public DragScaleView(Context context) {
        super(context);
        setOnTouchListener(this);
        initScreenW_H();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        paint.setColor(Color.GRAY);
        paint.setStrokeWidth(4.0f);
        paint.setStyle(Paint.Style.STROKE);
    }

    @Override
    public boolean onTouch(View v, MotionEvent event) {
//        setBackgroundResource(R.mipmap.splash);
        int action = event.getAction() & MotionEvent.ACTION_MASK;
        if (action == MotionEvent.ACTION_DOWN) {
            oriLeft = v.getLeft();
            oriRight = v.getRight();
            oriTop = v.getTop();
            oriBottom = v.getBottom();
            lastY = (int) event.getRawY();
            lastX = (int) event.getRawX();
            dragDirection = getDirection(v, (int) event.getX(),
                    (int) event.getY());
        }
        if (action == MotionEvent.ACTION_POINTER_DOWN) {
            oriLeft = v.getLeft();
            oriRight = v.getRight();
            oriTop = v.getTop();
            oriBottom = v.getBottom();
            lastY = (int) event.getRawY();
            lastX = (int) event.getRawX();
            dragDirection = TOUCH_TWO;
            oriDis = distance(event);
        }
        // 处理拖动事件
        delDrag(v, event, action);
        invalidate();
        return false;
    }

    /**
     * 处理拖动事件
     */
    protected void delDrag(View v, MotionEvent event, int action) {
        switch (action) {
            case MotionEvent.ACTION_MOVE:
                int dx = (int) event.getRawX() - lastX;
                int dy = (int) event.getRawY() - lastY;
                switch (dragDirection) {
                    case LEFT: // 左边缘
                        left(v, dx);
                        break;
                    case RIGHT: // 右边缘
                        right(v, dx);
                        break;
                    case BOTTOM: // 下边缘
                        bottom(v, dy);
                        break;
                    case TOP: // 上边缘
                        top(v, dy);
                        break;
                    case CENTER: // 点击中心-->>移动
                        center(v, dx, dy);
                        break;
                    case LEFT_BOTTOM: // 左下
                        left(v, dx);
                        bottom(v, dy);
                        break;
                    case LEFT_TOP: // 左上
                        left(v, dx);
                        top(v, dy);
                        break;
                    case RIGHT_BOTTOM: // 右下
                        right(v, dx);
                        bottom(v, dy);
                        break;
                    case RIGHT_TOP: // 右上
                        right(v, dx);
                        top(v, dy);
                        break;
                    case TOUCH_TWO: //双指操控
                        float newDist = distance(event);
                        float scale = newDist / oriDis;
                        //控制双指缩放的敏感度
                        int distX = (int) (scale * (oriRight - oriLeft) - (oriRight - oriLeft)) / 50;
                        int distY = (int) (scale * (oriBottom - oriTop) - (oriBottom - oriTop)) / 50;
                        if (newDist > 10f) {//当双指的距离大于10时，开始相应处理
                            left(v, -distX);
                            top(v, -distY);
                            right(v, distX);
                            bottom(v, distY);
                        }
                        break;

                }
                if (dragDirection != CENTER) {
                    v.layout(oriLeft, oriTop, oriRight, oriBottom);
                }
                lastX = (int) event.getRawX();
                lastY = (int) event.getRawY();
                break;
            case MotionEvent.ACTION_UP:
            case MotionEvent.ACTION_POINTER_UP:
                dragDirection = 0;
                break;

        }

        Log.d(TAG, "delDrag: x==" + lastX + "    ,y=" + lastY);

    }

    /**
     * TODO:最后X坐标值
     */
    public static int getLastX() {
        return lastX;
    }

    /**
     * TODO:最后Y坐标值
     */
    public static int getLastY() {
        return lastY;
    }

    /**
     * TODO: 获取缩放后的宽
     */
    public int getZoomWidth() {
//        ViewGroup.LayoutParams layoutParams = getLayoutParams();
//        int width = layoutParams.width;
        int width = mZoomWidth;
        return width;
    }

    /**
     * TODO: 获取缩放后的高
     */
    public int getZoomHeight() {
//        ViewGroup.LayoutParams layoutParams = getLayoutParams();
//        int width = layoutParams.width;
        int height = mZoomHeight;
        return height;
    }

    @Override
    protected void onSizeChanged(int w, int h, int oldw, int oldh) {
        super.onSizeChanged(w, h, oldw, oldh);

        //TODO:
        mZoomWidth = w;//获取到修改后的宽
        mZoomHeight = h;//获取到修改后的高

    }

    /**
     * 触摸点为中心->>移动
     *
     * @param v
     * @param dx
     * @param dy
     */
    private void center(View v, int dx, int dy) {
        int left = v.getLeft() + dx;
        int top = v.getTop() + dy;
        int right = v.getRight() + dx;
        int bottom = v.getBottom() + dy;
        if (left < -offset) {
            left = -offset;
            right = left + v.getWidth();
        }
        if (right > screenWidth + offset) {
            right = screenWidth + offset;
            left = right - v.getWidth();
        }
        if (top < -offset) {
            top = -offset;
            bottom = top + v.getHeight();
        }
        if (bottom > screenHeight + offset) {
            bottom = screenHeight + offset;
            top = bottom - v.getHeight();
        }
        Log.d("raydrag", left + "  " + top + "  " + right + "  " + bottom + "  " + dx);
        v.layout(left, top, right, bottom);
    }

    /**
     * 触摸点为上边缘
     *
     * @param v
     * @param dy
     */
    private void top(View v, int dy) {
        oriTop += dy;
        if (oriTop < -offset) {
            //对view边界的处理，如果子view达到父控件的边界，offset代表允许超出父控件多少
            oriTop = -offset;
        }
        if (oriBottom - oriTop - 2 * offset < 200) {
            oriTop = oriBottom - 2 * offset - 200;
        }
    }

    /**
     * 触摸点为下边缘
     *
     * @param v
     * @param dy
     */
    private void bottom(View v, int dy) {
        oriBottom += dy;
        if (oriBottom > screenHeight + offset) {
            oriBottom = screenHeight + offset;
        }
        if (oriBottom - oriTop - 2 * offset < 200) {
            oriBottom = 200 + oriTop + 2 * offset;
        }
    }

    /**
     * 触摸点为右边缘
     *
     * @param v
     * @param dx
     */
    private void right(View v, int dx) {
        oriRight += dx;
        if (oriRight > screenWidth + offset) {
            oriRight = screenWidth + offset;
        }
        if (oriRight - oriLeft - 2 * offset < 200) {
            oriRight = oriLeft + 2 * offset + 200;
        }
    }

    /**
     * 触摸点为左边缘
     *
     * @param v
     * @param dx
     */
    private void left(View v, int dx) {
        oriLeft += dx;
        if (oriLeft < -offset) {
            oriLeft = -offset;
        }
        if (oriRight - oriLeft - 2 * offset < 200) {
            oriLeft = oriRight - 2 * offset - 200;
        }
    }

    /**
     * 获取触摸点flag
     *
     * @param v
     * @param x
     * @param y
     * @return
     */
    protected int getDirection(View v, int x, int y) {
        int left = v.getLeft();
        int right = v.getRight();
        int bottom = v.getBottom();
        int top = v.getTop();
        if (x < touchDistance && y < touchDistance) {
            return LEFT_TOP;
        }
        if (y < touchDistance && right - left - x < touchDistance) {
            return RIGHT_TOP;
        }
        if (x < touchDistance && bottom - top - y < touchDistance) {
            return LEFT_BOTTOM;
        }
        if (right - left - x < touchDistance && bottom - top - y < touchDistance) {
            return RIGHT_BOTTOM;
        }
        if (x < touchDistance) {
            return LEFT;
        }
        if (y < touchDistance) {
            return TOP;
        }
        if (right - left - x < touchDistance) {
            return RIGHT;
        }
        if (bottom - top - y < touchDistance) {
            return BOTTOM;
        }
        return CENTER;
    }

    /**
     * 计算两个手指间的距离
     *
     * @param event 触摸事件
     * @return 放回两个手指之间的距离
     */
    private float distance(MotionEvent event) {
        float x = event.getX(0) - event.getX(1);
        float y = event.getY(0) - event.getY(1);
        return (float) Math.sqrt(x * x + y * y);//两点间距离公式
    }
}