xCode ios5：如何在间隔后淡出标签文本？ [英] xCode ios5: How to fade out a label text after an interval?

问题描述

我有一个显示图像的iOS5小应用程序。我点击图片显示其信息。我希望这些信息在几秒钟后消失。有没有一个很好的方法来做到这一点？

I have a little iOS5 app that shows images. I click on the image to show its information. I'd like the information to fade away after a few seconds. Is there a good method to do this?

我总是可以实现另一个按钮动作，但这样会更整洁..

I can always implement another button action but this would be neater..

谢谢！

推荐答案

使用 NSTimer 或 performSelector：withObject：afterDelay 。这两种方法都要求你调用一个实际上会逐渐淡出的单独方法，这个方法应该相当简单。

Use either NSTimer or performSelector:withObject:afterDelay. Both methods require you to call a separate method that will actually do the fading out which should be fairly straightforward.

NSTimer

[NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(fadeOutLabels:) userInfo:nil repeats:NO];

performSelector：withObject：afterDelay：

/* starts the animation after 3 seconds */
[self performSelector:@selector(fadeOutLabels) withObject:nil afterDelay:3.0f];

您将调用方法 fadeOutLabels （或任何你想称之为的）

-(void)fadeOutLabels
{
    [UIView animateWithDuration:1.0 
                          delay:0.0  /* do not add a delay because we will use performSelector. */
                        options:UIViewAnimationCurveEaseInOut 
                     animations:^ {
                         myLabel1.alpha = 0.0;
                         myLabel2.alpha = 0.0;
                     } 
                     completion:^(BOOL finished) {
                         [myLabel1 removeFromSuperview];
                         [myLabel2 removeFromSuperview];
                     }];
}

或者您可以使用动画块来完成所有工作：

Or you can use the animation block to do all of the work:

-(void)fadeOutLabels
{
    [UIView animateWithDuration:1.0 
                          delay:3.0  /* starts the animation after 3 seconds */
                        options:UIViewAnimationCurveEaseInOut 
                     animations:^ {
                         myLabel1.alpha = 0.0;
                         myLabel2.alpha = 0.0;
                     } 
                     completion:^(BOOL finished) {
                         [myLabel1 removeFromSuperview];
                         [myLabel2 removeFromSuperview];
                     }];
}

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