objective-c - iOS 滑动动画意外发生两次

Question

我正在使用 Xcode 4.4 和 ARC 开发基于页面的 iPhone 应用程序，并且已经在这方面停留了一段时间。在某个页面上，UIImageView手指需要向上滑动并指向某物，然后向左滑动离开屏幕。当我运行一次时，它按预期工作，但是当我翻页并返回时 - 现在有 2 个手指彼此滑动约 0.5 秒，不同步。

代码如下:

-(void)fingerSwipeUp:(UIImageView *)imageView
{
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:1];
    [imageView setCenter:CGPointMake(213.75,355.5)];
    [UIView commitAnimations];
}

-(void)fingerSwipeLeft:(UIImageView *)imageView
{
    [UIView beginAnimations:nil context:nil];
    [UIView setAnimationDuration:1];
    [imageView setCenter:CGPointMake(-80,355.5)];
    [UIView commitAnimations];
}

UIImageView *finger = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"finger.png"]];

// position finger off the screen
[finger setFrame:CGRectMake(142.5,480,152.5,243)];
[self.view addSubview:finger];

[self performSelector:@selector(fingerSwipeUp:) withObject:finger afterDelay:6];
[self performSelector:@selector(fingerSwipeLeft:) withObject:finger afterDelay:8];

非常感谢任何帮助

Answer 1

我猜您正在 ViewDidAppear() 中创建“手指” View ？如果是这种情况，每次翻页(隐藏)然后返回时，您都会添加另一个箭头( subview )。那么这个呢:

if (finger == nil) {
    finger = [[UIImageView alloc] initWithImage:[UIImage imageNamed:@"finger.png"]];
    [finger setFrame:CGRectMake(142.5,480,152.5,243)];
    [self.view addSubview:finger];
}

[self performSelector:@selector(fingerSwipeUp:) withObject:finger afterDelay:6];
[self performSelector:@selector(fingerSwipeLeft:) withObject:finger afterDelay:8];