blocks|key|1892090|text|下面的代码会给你的标签带来淡入淡出的效果。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1892091|+-+(IBAction)buttonClicked:(UIButton+*)sender
++{
++++labelMain.alpha+=+0;

++++[UIView+animateWithDuration:0.5+delay:0+options:UIViewAnimationOptionCurveEaseIn
++++animations:%5E{+labelMain.alpha+=+1;}
++++completion:nil];
+}|code-block|syntax|javascript|1892092|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

The following code will give you fading effect on your label.

<pre><code> - (IBAction)buttonClicked:(UIButton *)sender
 {
 labelMain.alpha = 0;

 [UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseIn
 animations:^{ labelMain.alpha = 1;}
 completion:nil];
 }
</code></pre>

blocks|key|4258249|text|我知道这有点过时(11个月前)，但我认为值得一提的是其他方法的替代方案，我觉得这是一个更好的解决方案。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4258250|使用UIView+transitionWithView:duration:options:animations:completion类级方法，如下所示：|offset|length|style|CODE|4258251|NSTimeInterval+duration+=+0.5f;
[UIView+transitionWithView:labelMain
++++++++++++++++++duration:duration
+++++++++++++++++++options:UIViewAnimationOptionTransitionCrossDissolve
++++++++++++++++animations:%5E{
++++++++++++++++++labelMain.text+=+@"new+value";
++++++++++++++++}+completion:nil];|code-block|syntax|javascript|4258252|这将从先前的labelMain.text值交叉淡入淡出为“新值”。|4258253|这种方法也适用于其他视图值，例如，更改UIImageView的图像。|4258254|有关此主题，请参阅Apple's+docs。|4258255|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.apple.com/library/ios/documentation/uikit/reference/uiview_class/UIView/UIView.html#//apple_ref/doc/uid/TP40006816-CH3-SW112^0|0|2|1S|0|0|6|E|0|0|9|C|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@$D|12|E|13|F|G]]|9|@]|A|$]]|$1|H|3|I|5|J|7|14|8|@]|9|@]|A|$K|L]]|$1|M|3|N|5|6|7|15|8|@$D|16|E|17|F|G]]|9|@]|A|$]]|$1|O|3|P|5|6|7|18|8|@]|9|@]|A|$]]|$1|Q|3|R|5|6|7|19|8|@]|9|@$D|1A|E|1B|1|1C]]|A|$]]|$1|S|3|-4|5|6|7|1D|8|@]|9|@]|A|$]]]|T|$U|$5|V|W|X|A|$Y|Z]]]]

I know this is a bit stale (11 months old), but I think it's worth mentioning an alternative to the other approaches posted, which I feel is a better solution.

Make use of the <code>UIView transitionWithView:duration:options:animations:completion</code> class-level method, like this:

<pre><code>NSTimeInterval duration = 0.5f;
[UIView transitionWithView:labelMain
 duration:duration
 options:UIViewAnimationOptionTransitionCrossDissolve
 animations:^{
 labelMain.text = @"new value";
 } completion:nil];
</code></pre>

This will cross-fade from the previous value of <code>labelMain.text</code> to "new value".

This approach works on other view values as well, such as changing the image of a UIImageView, for instance.

See <a href="https://developer.apple.com/library/ios/documentation/uikit/reference/uiview_class/UIView/UIView.html#//apple_ref/doc/uid/TP40006816-CH3-SW112">Apple's docs</a> on the topic.

blocks|key|2132059|text|label.text+=+@"old+text";
++++[UIView+animateWithDuration:0.4+animations:%5E{
++++++++label.alpha+=+0.0f;
++++}+completion:%5E(BOOL+finished)+{
++++++++label.text+=+@"next+text";
++++++++[UIView+animateWithDuration:0.4+animations:%5E{
++++++++++++label.alpha+=+1.0f;
++++++++}+completion:%5E(BOOL+finished)+{
++++++++++++NSLog(@"finished+transition");
++++++++}];
++++}];|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|2132060|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>label.text = @"old text";
 [UIView animateWithDuration:0.4 animations:^{
 label.alpha = 0.0f;
 } completion:^(BOOL finished) {
 label.text = @"next text";
 [UIView animateWithDuration:0.4 animations:^{
 label.alpha = 1.0f;
 } completion:^(BOOL finished) {
 NSLog(@"finished transition");
 }];
 }];
</code></pre>

blocks|key|4258192|text|试试这个：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4258193|[labelMain+setAlpha:0];
[UIView+beginAnimations:nil+context:NULL];
[UIView+setAnimationDuration:0.8];
[labelMain+setAlpha:1];
[UIView+commitAnimations];|code-block|syntax|javascript|4258194|更改持续时间非常简单-只需在代码中调整值0.8即可。|offset|length|style|CODE|4258195|entityMap^0|0|0|K|3|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Try this:

<pre><code>[labelMain setAlpha:0];
[UIView beginAnimations:nil context:NULL];
[UIView setAnimationDuration:0.8];
[labelMain setAlpha:1];
[UIView commitAnimations];
</code></pre>

Changing the duration is pretty simple - just adjust the value <code>0.8</code> in the code.

blocks|key|4258212|text|//+fade+out+the+current+value
[UIView+animateWithDuration:0.2
++++++++++++++++++++++delay:0
++++++++++++++++++++options:0
+++++++++++++++++animations:%5E{
+++++++++++++++++++labelMain.alpha+=+0.0f;
+++++++++++++++++}
+++++++++++++++++completion:%5E(BOOL+finished)+{
+++++++++++++++++++//+set+the+new+value+and+fade+in
+++++++++++++++++++labelMain.text+=+newValue;
+++++++++++++++++++[UIView+animateWithDuration:0.2
+++++++++++++++++++++++++++++++++++++++++delay:0
+++++++++++++++++++++++++++++++++++++++options:0
++++++++++++++++++++++++++++++++++++animations:%5E{
++++++++++++++++++++++++++++++++++++++labelMain.alpha+=+1.0f;
++++++++++++++++++++++++++++++++++++}
++++++++++++++++++++++++++++++++++++completion:nil];

+++++++++++++++++}];|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4258213|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>// fade out the current value
[UIView animateWithDuration:0.2
 delay:0
 options:0
 animations:^{
 labelMain.alpha = 0.0f;
 }
 completion:^(BOOL finished) {
 // set the new value and fade in
 labelMain.text = newValue;
 [UIView animateWithDuration:0.2
 delay:0
 options:0
 animations:^{
 labelMain.alpha = 1.0f;
 }
 completion:nil];

 }];
</code></pre>

blocks|key|1892127|text|这看起来像是交叉淡入淡出动画|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1892128|+[UIView+animateWithDuration:0.5+delay:0+options:UIViewAnimationOptionCurveEaseOut
++++++++animations:%5E{
++++labelMain.alpha+=+0;

++++++++[UIView+animateWithDuration:0.5+delay:0+options:UIViewAnimationOptionCurveEaseIn
++++++++animations:%5E{+labelMain.alpha+=+1;}
++++++++completion:nil];

++++}+completion:nil];|code-block|syntax|javascript|1892129|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This will look like cross fade animation 

<pre><code> [UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseOut
 animations:^{
 labelMain.alpha = 0;

 [UIView animateWithDuration:0.5 delay:0 options:UIViewAnimationOptionCurveEaseIn
 animations:^{ labelMain.alpha = 1;}
 completion:nil];

 } completion:nil];
</code></pre>

Right now I have an IBAction for a button which generates a random number with each number assigned to display text in a UILabel. Rather than just appear, I would like the text to fade in or any other interesting animation would be cool too. Does anyone know a simple way to make this happen? 

Right now I just use

<pre><code>labelMain.text = @"my text";
</code></pre>

How do I have text fade in to a UILabel?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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现在，我有一个按钮的IBAction，它生成一个随机数，每个数字都分配给在UILabel中显示文本。而不是仅仅出现，我希望文本淡入或任何其他有趣的动画将是很酷的。有谁知道一种简单的方法来实现这一点吗？现在我只是使用labelMain.text = @"my text";

问如何让文本淡入UILabel？
EN

回答 6

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问如何让文本淡入UILabel？EN

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问如何让文本淡入UILabel？
EN