ios - UIView按预期用animateWithDuration对setBackgroundColor进行动画处理。但是，UILabel立即发生。为什么？

Question

我要实现的目标是:拥有多个UILabel并能够依次突出显示它们，这意味着我想更改它们的textColor，fontSize和位置。因此，我已经成功编写了一个演示，该演示接受一组UIView并依次突出显示它们(更改了backgroundColor)。

阅读了Andrew Fuchs对引用Best Way to Perform Several Sequential UIView Animations?的Multiple UIView Animations Without Nested Blocks问题的答复

但是，当我在代码中用UILabel代替UIView时，所有内容都掉了下来，而且它们都不是动画，因此更改立即发生。谁能告诉我我在做什么错？ UILabel是UIView的子类，因此我希望UIView中可以使用的属性可以在UILabel中使用。在Apple的“iOS的View编程指南-动画”中，指出backgroundColor可以被动画化。因此，我回到基础知识，编写了一些测试代码，发现对于UIView，我可以愉快地为其backgroundColor，alpha和中心位置设置动画。 UILabel alpha属性和中心位置可以成功设置动画，而backgroundColor和textColor无法设置动画。另请:GitHub AnimateSequentially

- (void)viewDidLoad {
    [super viewDidLoad];

    duration = 2.0;
    yOffset = 100.0;
    normalColor = [UIColor lightGrayColor];
    highlightedColor = [UIColor greenColor];
    view1StartPoint = view1.center;
    view2StartPoint = view2.center;
    lable1StartPoint = label1.center;
    lable2StartPoint = label2.center;
    [self resetEverything:nil];
}

- (IBAction)animateViews:(id)sender
{
    [UIView animateWithDuration:duration
                     animations:^{
                         [view1 setBackgroundColor:highlightedColor];       // animates correctly
//                         [view1 setAlpha:0.2];                              // animates correctly
                         CGPoint p = view1.center;
                         p.y -= yOffset;
                         view1.center = p;                                 // animates correctly
                     }
                     completion:^(BOOL finished){
                         [UIView animateWithDuration:duration
                                          animations:^{
                                              [view2 setBackgroundColor:highlightedColor];
//                                              [view2 setAlpha:0.2];
                                              CGPoint p = view2.center;
                                              p.y -= yOffset;
                                              view2.center = p;                                 // animates correctly
                                          }
                                          completion:nil];
                     }
     ];
}

- (IBAction)animateLabelsSimple:(id)sender      // does NOT works sequentially
{
    [UIView animateWithDuration:duration
                     animations:^{
                         [label1 setBackgroundColor:highlightedColor];      // changes instantly
//                         [label1 setTextColor:[UIColor orangeColor]];       // changes instantly
//                         [label1 setAlpha:0.2];                             // animates correctly
                         CGPoint p = label1.center;
                         p.y -= yOffset;
                         label1.center = p;                                 // animates correctly
                     }
                     completion:^(BOOL finished){
                         [UIView animateWithDuration:duration
                                          animations:^{
                                              [label2 setBackgroundColor:highlightedColor];
//                                              [label2 setTextColor:[UIColor orangeColor]];
//                                              [label2 setAlpha:0.2];
                                              CGPoint p = label2.center;
                                              p.y -= yOffset;
                                              label2.center = p;
                                          }
                                          completion:nil];
                     }
     ];
}

- (IBAction)resetEverything:(id)sender
{
    [view1 setBackgroundColor:normalColor];
    [view2 setBackgroundColor:normalColor];
    [label1 setBackgroundColor:normalColor];
    [label2 setBackgroundColor:normalColor];

    [view1 setAlpha:1.0];
    [view2 setAlpha:1.0];
    [label1 setAlpha:1.0];
    [label2 setAlpha:1.0];

    [label1 setTextColor:[UIColor blackColor]];
    [label2 setTextColor:[UIColor blackColor]];

    view1.center = view1StartPoint;
    view2.center = view2StartPoint;
    label1.center = lable1StartPoint;
    label2.center = lable2StartPoint;
}

我查看了GitHub Chameleon项目，并了解了如何实现UIView类方法“animateWithDuration”:

+ (void)animateWithDuration:(NSTimeInterval)duration delay:(NSTimeInterval)delay options:(UIViewAnimationOptions)options animations:(void (^)(void))animations completion:(void (^)(BOOL finished))completion
{
    [self _beginAnimationsWithOptions:options | UIViewAnimationOptionTransitionNone];
    [self setAnimationDuration:duration];
    [self setAnimationDelay:delay];
    [self _setAnimationCompletionBlock:completion];

    animations();

    [self commitAnimations];
}

那么，我是否必须继承UILabel并重写animateWithDuration方法？或最好的方法是什么？

Answer 1

您可以尝试使用https://stackoverflow.com/a/20892927/4030971通过动画更改uilabel的颜色。上面您已经实现了此功能，但需要进行一些更改。也可以尝试一下

[UIView animateWithDuration:duration animations:^{
     [view1 setBackgroundColor:highlightedColor];       
     [view1 setAlpha:0.2];
     [label setAlpha:0.0];                             
     CGPoint p = view1.center;
     p.y -= yOffset;
     view1.center = p;
}completion:^(BOOL finished){
     if(finished){
         [label setBackgroundColor:[UIColor redColor]];
         [UIView animateWithDuration:duration animations:^{
             [view2 setBackgroundColor:highlightedColor];
             [view2 setAlpha:0.2];
             [label setAlpha:1.0];
             CGPoint p = view2.center;
             p.y -= yOffset;
             view2.center = p;
         }completion:nil];
}];

您可以在Alpha为0时编写标签颜色更改代码，然后可以通过使Alpha 1来为标签设置动画。颜色更改代码将在“是否完成”检查之后和“下一个动画”开始块之前进行。