ios开发之--找window，获取屏幕最上层的窗口

UIWindow *window = [[[UIApplication sharedApplication] delegate] window];

UIWindow *window = [[[UIApplication sharedApplication] windows] lastObject];

UIView *aView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 150, 300)];
aView.backgroundColor = [UIColor redColor];
// 当前顶层窗口
UIWindow *window = [[UIApplication sharedApplication].windows lastObject];
// 添加到窗口
[window addSubview:aView];