iOS 退出应用

用动画的形式退出应用 

- (void)viewDidLoad {
    [super viewDidLoad];
    UIButton *btn = [UIButton buttonWithType:(UIButtonTypeCustom)];
    [btn setTitle:@"退出" forState:(UIControlStateNormal)];
    [btn setTitleColor:[UIColor whiteColor] forState:(UIControlStateNormal)];
    btn.frame = CGRectMake(100, 100, 100, 30);
    btn.backgroundColor = [UIColor redColor];
    [btn addTarget:self action:@selector(exitApplication) forControlEvents:(UIControlEventTouchUpInside)];
    [self.view addSubview:btn];
}
- (void)exitApplication {
    UIWindow *window = [UIApplication sharedApplication].keyWindow;
    [UIView beginAnimations:@"exitApplication" context:nil];
    [UIView setAnimationDuration:1];
    [UIView setAnimationDelegate:self];
    [UIView setAnimationTransition:UIViewAnimationTransitionFlipFromRight forView:window cache:NO];
    [UIView setAnimationDidStopSelector:@selector(animationFinished:finished:context:)];
    window.bounds = CGRectMake(0, 0, 0, 0);
    [UIView commitAnimations];
}
- (void)animationFinished:(NSString *)animationID finished:(NSNumber *)finished context:(void *)context {
    if ([animationID compare:@"exitApplication"] == 0) {
        exit(0);
    }
}