启动动画渐变扩大并消失

 //启动动画渐变扩大并消失，此段代码写在AppDelegate启动方法最底下，覆盖在Window上。消失后就移除掉

    UIImageView*splashScreen = [[UIImageView alloc]initWithFrame:self.window.bounds];

    splashScreen.image =[UIImage imageNamed:@"begin.png"];

    [self.windowaddSubview:splashScreen];

    [UIViewanimateWithDuration:3.0f animations:^{

       splashScreen.layer.transform =CATransform3DMakeScale(1.5, 1.5, 1.0);

       splashScreen.alpha = 0;

    } completion:^(BOOLfinished) {

       [splashScreen removeFromSuperview];

    }];