Android 限制父边界内的子视图

我正在创建一个矩形框，并在其中放置一个可以移动的imageView。在进行onMove时，我注意到imageView超出了它的父视图的范围，这是我不想要的。我想将imageView限制在其父视图的边界内。如何做到这一点

以下是xml：

---

在被覆盖的

onTouch

中，您需要检查以下移动是否会将

ImageView

保留在其容器中

换句话说，您需要检查在被dx，dy移动后，

ImageView

的矩形是否会留在父对象内

下面是一个例子：

case MotionEvent.ACTION_MOVE:
    ...
    // Calculate the distance moved
    final float dx = x1 - mLastTouchX;
    final float dy = y1 - mLastTouchY;

    // Make sure we will still be the in parent's container
    Rect parent = new Rect(0, 0, root.getWidth(), root.getHeight());

    int newLeft = (int) (iv.getX() + dx),
            newTop = (int) (iv.getY() + dy),
            newRight = newLeft + iv.getWidth(),
            newBottom = newTop + iv.getHeight();

    if (!parent.contains(newLeft, newTop, newRight, newBottom)) {
        Log.e(TAG, String.format("OOB @ %d, %d - %d, %d",
                newLeft, newTop, newRight, newBottom));
        break;
    }
    ...

---

还要注意的是，您不需要使容器无效，因为setX/setY会使

ImageView

本身无效。

工作起来很有魅力。谢谢。你能告诉我我们想要在边界内拖动一个视图吗，这样一旦父视图和子视图边界匹配，它就不会移动。这段代码中的mPosX是什么？

@Override
public boolean onTouch(View view, MotionEvent event) {
    switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            final float x = event.getRawX();
            final float y = event.getRawY();

            // Remember where we started
            mLastTouchX = x;
            mLastTouchY = y;

            break;
        case MotionEvent.ACTION_UP:
            break;
        case MotionEvent.ACTION_POINTER_DOWN:
            break;
        case MotionEvent.ACTION_POINTER_UP:
            break;
        case MotionEvent.ACTION_MOVE:


            final float x1 = event.getRawX();
            final float y1 = event.getRawY();

            // Calculate the distance moved
            final float dx = x1 - mLastTouchX;
            final float dy = y1 - mLastTouchY;

            // Move the object
            mPosX += dx;
            mPosY += dy;
            view.setX(mPosX);
            view.setY(mPosY);

            // Remember this touch position for the next move event
            mLastTouchX = x1;
            mLastTouchY = y1;

            // Invalidate to request a redraw
            root.invalidate();
            break;
    }
    return true;
}}

case MotionEvent.ACTION_MOVE:
    ...
    // Calculate the distance moved
    final float dx = x1 - mLastTouchX;
    final float dy = y1 - mLastTouchY;

    // Make sure we will still be the in parent's container
    Rect parent = new Rect(0, 0, root.getWidth(), root.getHeight());

    int newLeft = (int) (iv.getX() + dx),
            newTop = (int) (iv.getY() + dy),
            newRight = newLeft + iv.getWidth(),
            newBottom = newTop + iv.getHeight();

    if (!parent.contains(newLeft, newTop, newRight, newBottom)) {
        Log.e(TAG, String.format("OOB @ %d, %d - %d, %d",
                newLeft, newTop, newRight, newBottom));
        break;
    }
    ...