获取最后一个Window层

+ (UIWindow *)lastWindow
{
    NSEnumerator *frontToBackWindows = [UIApplication.sharedApplication.windows reverseObjectEnumerator];
    for (UIWindow *window in frontToBackWindows) {
        BOOL windowOnMainScreen = window.screen == UIScreen.mainScreen;
        BOOL windowIsVisible = !window.hidden && window.alpha > 0;
        BOOL windowLevelSupported = (window.windowLevel >= UIWindowLevelNormal && window.windowLevel <= UIWindowLevelNormal);
        BOOL windowKeyWindow = window.isKeyWindow;
        
        if(windowOnMainScreen && windowIsVisible && windowLevelSupported && windowKeyWindow) {
            return window;
        }
    }

    return nil;
}