NStimer

    _myTimer = [NSTimer timerWithTimeInterval:3.0 target:self selector:@selector(timerFired) userInfo:nil repeats:NO];

    [[NSRunLoop  currentRunLoop] addTimer:_myTimer forMode:NSDefaultRunLoopMode];

[_myTimer invalidate];移除timer

    3秒后执行

-(void)timerFired

{

    DebugLog(@"ok");

    UIWindow *window = [UIApplication sharedApplication].keyWindow;

    window.rootViewController = [[WrapperMainViewController alloc] init];

}