Question

在我的iOS应用程序中，我想创建一个UILabel的等效物，可以突出显示，以便简单地引起对自身的注意。所以我希望它在脉动的同时将其颜色从蓝色变为红色。所以我增加然后将fontSize减少20％，因此我还需要更改AnchorPoint，使其看起来从中心向所有方向均匀向外扩展。我已经设法编写实现所有这些目标的代码，只有在我创建对象时执行它。但是，当我通过按下按钮通过IBAction调用它时，colorChange和fontSizeChange无效，而anchorPointChange继续工作。我不知道我做错了什么，虽然我的问题的原因可能很明显，我没有发现它。我尝试了各种代码的实现，子类化UIView和使用CALayer类，但是为了提供一个简洁的例子，我在这里将它全部打包到viewDidLoad中。

任何帮助都将非常感激。

OSX Yosemite版本10.10（14A389），Xcode版本6.1（6A1052d），iOS模拟器版本8.1（550.3）

#import "ViewController.h"

@interface ViewController ()
@property (strong, nonatomic) CATextLayer *textLayer;
@end

@implementation ViewController
@synthesize textLayer;
float animationDuration;

- (void)viewDidLoad {
    [super viewDidLoad];

    textLayer = [CATextLayer layer];
    [textLayer setString: @"AB"];
    [textLayer setForegroundColor: [UIColor blueColor].CGColor];
    [textLayer setFontSize: 50.0];
    [textLayer setAlignmentMode: kCAAlignmentCenter];
    [textLayer setFrame: CGRectMake(100, 150, 100, 60)];
    [textLayer setPosition: CGPointMake(CGRectGetMidX(textLayer.frame), CGRectGetMidY(textLayer.frame))];
    [textLayer setAnchorPoint: CGPointMake(0.5, 0.5)];
    [[self.view layer] addSublayer:textLayer];

    UIButton *activationButton = [UIButton buttonWithType:UIButtonTypeRoundedRect];
    activationButton.backgroundColor = [UIColor lightGrayColor];
    activationButton.frame = CGRectMake(130.0, 250.0, 150.0, 30.0);
    [activationButton setTitle:@"Highlight Label" forState:UIControlStateNormal];
    [activationButton addTarget:self action:@selector(highlightLabel:) forControlEvents:UIControlEventTouchUpInside];
    [self.view addSubview:activationButton];

    animationDuration = 2.0;
//    [self changeColor];                           // all three methods work perfectly, if called here
//    [self changeFontSize: 50.0 scale: 1.2];
//    [self changeAnchorPointFrom: CGPointMake(0.5, 0.5) to: CGPointMake(0.5, 0.6)];
/*    [self highlightLabel: nil]; */
}

- (IBAction) highlightLabel: (UIButton *) sender {
    NSLog(@" textLayer.string: %@", textLayer.string);
    [self changeColor];                                                                 // Has no effect
    [self changeFontSize: 50.0 scale: 1.2];                                             // Has no effect
    [self changeAnchorPointFrom: CGPointMake(0.5, 0.5) to: CGPointMake(0.5, 0.6)];      // Only this method call works
}

- (void)changeFontSize: (float) fontSize scale: (float)factor
{
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"fontSize"];
    animation.duration = animationDuration;
    animation.removedOnCompletion = NO;
    animation.autoreverses = YES;
    animation.fromValue = @(fontSize);
    animation.toValue = @(fontSize * factor);
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    [textLayer addAnimation:animation forKey:@"fontSizeAnimation"];
}

- (void)changeAnchorPointFrom: (CGPoint) startPoint to: (CGPoint)endPoint
{
    CABasicAnimation *animation = [CABasicAnimation  animationWithKeyPath:@"anchorPoint"];
    animation.duration = animationDuration;
    animation.removedOnCompletion = NO;
    animation.autoreverses = YES;
    animation.fromValue = [NSValue valueWithCGPoint:startPoint];
    animation.toValue = [NSValue valueWithCGPoint:endPoint];
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    [textLayer addAnimation:animation forKey:@"anchorPointAnimation"];
}

- (void)changeColor
{
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"foregroundColor"];
    animation.duration = animationDuration * 2;
    animation.fillMode = kCAFillModeForwards;
    animation.removedOnCompletion = NO;
    animation.fromValue = (id)[UIColor blueColor].CGColor;
    animation.toValue = (id)[UIColor redColor].CGColor;
    animation.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
    [textLayer addAnimation:animation forKey:@"colorAnimation"];
}

@end

Answer 1

您需要设置文本图层的最终颜色，尝试在highlightLabel方法的末尾添加此颜色。

[CATransaction begin];
[CATransaction setDisableActions:YES];
[textLayer setForegroundColor: [UIColor redColor].CGColor];
[CATransaction commit];

CATextLayer属性的CABasicAnimation属性foregroundColor＆amp; fontSize有时无法正常工作

1 个答案: