performSelector：withObject：afterDelay方法無法正常工作？

Question

我有一個應用程序與一個小的uiimageview圈，淡入和淡出到兩個不同的位置。當用戶觸摸屏幕時，我希望圓圈立即淡出，並且我希望它不再進入移動位置。所以基本上觸摸屏幕殺死了圓圈。

雖然我想讓另一個圈子產卵並做同樣的事情（淡入和退出到2個不同的位置），直到用戶觸摸屏幕，然後我要這個圈子被殺死，而另一個圈子產卵等..

這裏是我的簡化代碼：

- (void)spawnCircle { 
    self.circle = [[UIImageView alloc]initWithFrame:self.rectCircle];//alocate it and give it its first frame 
    self.circle.image=[UIImage imageNamed:@"circle.png"];//make its image the circle image 
    [self.view addSubView:self.circle]; 
    [self performSelector:@selector(fadeCircleOut)withObject:self afterDelay:2];//the circle will fade out after 2 seconds 
    self.isFadeCircleOutNecessary=YES; 
} 

- (void)fadeCircleOut { 

    if (self.isFadeCircleOutNecessary){//because after the circle fades in this method is scheduled to occur after 2 seconds, well, if the user has touched the screen within that time frame we obviously don't want this method to be called because we already are fading it out 
     [UIView animateWithDuration:.5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{//the circle will fade out for a duration of .5 seconds 
      self.circle.alpha=0; 
     } completion:^(BOOL finished) { 
      if (finished) { 
       if (self.circle.frame.origin.x==self.rectCircle.origin.x) {//if its in the first location go to the second 
        self.circle.frame=self.rectCircle2; 

       }else{//if its in the second location go to the first 
        self.circle.frame=self.rectCircle; 
       } 
       [self fadeCircleIn];//now were going to immediately fade it in its new location 
      } 
     }]; 
    } 
} 

- (void)fadeCircleIn { 
    [UIView animateWithDuration:.5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{//fade it in with a duration of .5 seconds 
     self.circle.alpha=1; 
    } completion:^(BOOL finished) { 
     if (finished) { 
      [self performSelector:@selector(fadeCircleOut) withObject:self afterDelay:2];//after 2 seconds the object will fade out again 
     } 
    }]; 
} 

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 

    [UIView animateWithDuration:.5 delay:0 options:UIViewAnimationCurveLinear|UIViewAnimationOptionBeginFromCurrentState animations:^(){ self.circle.alpha=0;} completion:^(BOOL completion){//begin from current state makes it stop any animations it is currently in the middle of 

     [self spawnCircle];//now another circle will pop up 
     self.isFadeCircleOutNecessary=NO; 
    }]; 
} 

- (void)viewDidLoad { 
    [super viewDidLoad]; 
    [self spawnCircle]; 
} 

所以第一次圓派生這個偉大的工程，但下一次產卵圈（用戶觸摸屏幕，並殺死了第一圈後）淡出方法不會在2秒後發生，它在發生時會發生變化，但通常幾乎立即淡出。所以performSelector:withObject:afterDelay的延遲部分似乎不能正常工作

Answer 1

我嘗試了你的代碼，並得到了相同的結果。我不確定幕後的performSelector：withObject：afterDelay：會怎麼樣，但是看起來好像一旦你得到了一個，它仍然可以執行它的功能，即使你已經創建了另一個圓。

我通過擺脫afterDelay調用稍微改變了代碼，而是將2秒的延遲放在淡出方法中。看看這是否是你想要的：

-(void)spawnCircle{ 
    self.circle=[[UIImageView alloc]initWithFrame:self.rectCircle];//alocate it and give it its first frame 
    self.circle.image=[UIImage imageNamed:@"circle.png"];//make its image the circle image 
    [self.view addSubview:self.circle]; 
    [self fadeCircleOut]; 
} 

- (void)fadeCircleOut { 

    [UIView animateWithDuration:.5 delay:2 options:UIViewAnimationOptionCurveLinear animations:^{//the circle will fade out for a duration of .5 seconds 
     self.circle.alpha=0; 
    } completion:^(BOOL finished) { 
     if (finished) { 
      if (self.circle.frame.origin.x==self.rectCircle.origin.x) {//if its in the first location go to the second 
       self.circle.frame=self.rectCircle2; 

      }else{//if its in the second location go to the first 
       self.circle.frame=self.rectCircle; 
      } 
      [self fadeCircleIn];//now were going to immediately fade it in its new location 
     } 
    }]; 
} 

- (void)fadeCircleIn { 
    [UIView animateWithDuration:.5 delay:0 options:UIViewAnimationOptionCurveLinear animations:^{//fade it in with a duration of .5 seconds 
     self.circle.alpha=1; 
    } completion:^(BOOL finished) { 
     if (finished) { 
      [self fadeCircleOut]; 
     } 
    }]; 
} 

- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event { 
    [UIView animateWithDuration:.5 delay:0 options:UIViewAnimationCurveLinear|UIViewAnimationOptionBeginFromCurrentState animations:^{ 
     self.circle.alpha=0; 
    } 
        completion:^(BOOL completion){//begin from current state makes it stop any animations it is currently in the middle of 
         [self.circle removeFromSuperview]; 
         self.circle = nil; 
         [self spawnCircle]; 
    }]; 
}