iOS 简单动画 block动画

 - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event{
     UIView * view = [[UIView alloc]initWithFrame:CGRectMake(, , , )];
     view.backgroundColor = [UIColor orangeColor];
     view.alpha = ;
     [self.view addSubview:view];
     //动画持续时间为五秒
     [UIView animateWithDuration: animations:^{
         view.alpha = ;
     }completion:^(BOOL finished) {//当动画结束后进行的操作
         //动画时间为一秒
         [UIView animateWithDuration: animations:^{
             view.alpha = ;
         } completion:^(BOOL finished) {
             view.backgroundColor = [UIColor blueColor];
         }];
     }];
 }