UIApplication``` // 3.让应用程序可以接受远程事件 [[UIApplication sharedAp

// 3.让应用程序可以接受远程事件
 [[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

- (UIWindow *)appWindow {
    id<UIApplicationDelegate> delegate = UIApplication.sharedApplication.delegate;
    if ([delegate respondsToSelector:@selector(window)]) {
        return delegate.window;
    }
    return [UIApplication.sharedApplication keyWindow];
}