VisibilityAwareImageButton用法

我最近使用ImageButtons,我遇到了这种新型的ImageButton'VisibilityAwareImageButton'.如果有人能告诉我这个ImageButton的用法以及它与常规的ImageButton有什么不同,那将会非常有用？提前致谢 :)

这是完整的来源VisibilityAwareImageButton.

class VisibilityAwareImageButton extends ImageButton {

    private int mUserSetVisibility;

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

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

    public VisibilityAwareImageButton(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        mUserSetVisibility = getVisibility();
    }

    @Override
    public void setVisibility(int visibility) {
        internalSetVisibility(visibility, true);
    }

    final void internalSetVisibility(int visibility, boolean fromUser) {
        super.setVisibility(visibility);
        if (fromUser) {
            mUserSetVisibility = visibility;
        }
    }

    final int getUserSetVisibility() {
        return mUserSetVisibility;
    }
}

它似乎与常规几乎完全相同ImageButton,只是它跟踪用户实际设置的最后一次可见性.我能找到的唯一用法是在FloatingActionButton源代码中.它用于跟踪用户想要查看视图的内容,同时执行自己的内部更改和动画.即

if (child.getUserSetVisibility() != VISIBLE) {
    // The view isn't set to be visible so skip changing it's visibility
    return false;
}

它位于设计支持库中并具有包可见性,因此Google似乎打算在内部使用它(此时似乎仅用于FAB实现).