xCode ios5：如何在间隔后淡出标签文本？
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xCode ios5: How to fade out a label text after an interval?
提问by David DelMonte
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?
我有一个显示图像的小 iOS5 应用程序。我单击图像以显示其信息。我希望信息在几秒钟后消失。有没有好的方法可以做到这一点？
I can always implement another button action but this would be neater..
我总是可以实现另一个按钮操作，但这会更整洁..
Thanks!
谢谢！
回答by WrightsCS
Use either NSTimeror performSelector:withObject:afterDelay. Both methods require you to call a separate method that will actually do the fading out which should be fairly straightforward.
使用NSTimer或performSelector:withObject:afterDelay。这两种方法都要求您调用一个单独的方法，该方法实际上会进行淡出，这应该相当简单。
Example:
例子：
NSTimer
定时器
[NSTimer scheduledTimerWithTimeInterval:3.0 target:self selector:@selector(fadeOutLabels:) userInfo:nil repeats:NO];
performSelector:withObject:afterDelay:
performSelector:withObject:afterDelay:
/* starts the animation after 3 seconds */
[self performSelector:@selector(fadeOutLabels) withObject:nil afterDelay:3.0f];
And you will call the method fadeOutLabels(or whatever you want to call it)
您将调用该方法（或任何您想调用的方法fadeOutLabels）
-(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];
}];
}
Or you can use the animation block to do all of the work:
或者您可以使用动画块来完成所有工作：
-(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];
}];
}
