从 Android 的 ViewPager 中获得启示。
/**
* Tests scrollability within child views of v given a delta of dx.
*
* @param v View to test for horizontal scrollability
* @param checkV Whether the view v passed should itself be checked for scrollability (true),
* or just its children (false).
* @param dx Delta scrolled in pixels
* @param x X coordinate of the active touch point
* @param y Y coordinate of the active touch point
* @return true if child views of v can be scrolled by delta of dx.
*/
protected boolean canScroll(View v, boolean checkV, int dx, int x, int y) {
if (v instanceof ViewGroup) {
final ViewGroup group = (ViewGroup) v;
final int scrollX = v.getScrollX();
final int scrollY = v.getScrollY();
final int count = group.getChildCount();
// Count backwards - let topmost views consume scroll distance first.
for (int i = count - 1; i >= 0; i--) {
// TODO: Add versioned support here for transformed views.
// This will not work for transformed views in Honeycomb+
final View child = group.getChildAt(i);
if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight() &&
y + scrollY >= child.getTop() && y + scrollY < child.getBottom() &&
canScroll(child, true, dx, x + scrollX - child.getLeft(),
y + scrollY - child.getTop())) {
return true;
}
}
}
return checkV && ViewCompat.canScrollHorizontally(v, -dx);
}
它实际上遍历整个视图层次结构并进行命中测试以查看触摸是否位于视图边界内,如果是,则检查该视图是否可以滚动。