iOS APP 中查找显示在最上面的、全屏的、可见的 window（大部分情况都适用）

ZYWindowManager.m

- (UIWindow *)topFullScreenVisibleWindow
{
    NSArray *windows = [UIApplication sharedApplication].windows;
    for (UIWindow *window in windows.reverseObjectEnumerator) {
        if (window.hidden == YES || window.opaque == NO) {
            continue;
        }
        if (CGRectEqualToRect(window.bounds, [UIScreen mainScreen].bounds) == NO) {
            continue;
        }
        return window;
    }
    if ([UIApplication sharedApplication].keyWindow) {
        return [UIApplication sharedApplication].keyWindow;
    }
    if ([[UIApplication sharedApplication].delegate respondsToSelector:@selector(window)]) {
        return [UIApplication sharedApplication].delegate.window;
    }
    return nil;
}