动画NSMutableAttributedString颜色-字符串消失 [英] Animating NSMutableAttributedString color - the string disappears

问题描述

我有一个图层，并在其 drawInContext：中用 drawInRect：绘制了一个属性字符串。

I have a layer and in its drawInContext: I draw an attributed string with drawInRect:. Here's how I initialise the layer.

+ (id)layer
{
    Character *layer = [[self alloc] init];
    if (layer) {
        NSDictionary *attributes = @{NSFontAttributeName: [UIFont fontWithName:@"Fabada" size:72]};
        layer.symbol = [[NSMutableAttributedString alloc] initWithString:@"X" attributes:attributes];
    }
    return layer;
}

我想为字符串的颜色设置动画，所以我具有三个动态属性。 / p>

I want to animate the string's color, so I have three dynamics properties.

@interface Character : CALayer

@property (nonatomic, strong) NSMutableAttributedString *symbol;
@property (nonatomic) int red;
@property (nonatomic) int green;
@property (nonatomic) int blue;

@end

@implementation Character

@dynamic red;
@dynamic green;
@dynamic blue;

/* ... */

在draw方法中，I

In the draw method, I set the foreground color.

/* Set symbol color */
NSRange range = {0, [self.symbol length]};
UIColor *foreground = [UIColor colorWithRed:self.red    / 255.0
                                      green:self.green  / 255.0
                                       blue:self.blue   / 255.0
                                      alpha:1];
[self.symbol addAttribute:NSForegroundColorAttributeName value:foreground range:range];
CGRect symbolRect; /* The frame */
[self.symbol drawInRect:symbolRect];

该字符会根据需要显示在屏幕上。但是，一旦我在图层上添加了 CABasicAnimation ，该符号就会消失。

The character appears on screen as desired. But once I add a CABasicAnimation to the layer, the symbol just disappears.

CABasicAnimation *animation = [CABasicAnimation animation];
animation.duration = 10.0;
animation.fillMode = kCAFillModeForwards;
animation.removedOnCompletion = NO;
animation.delegate = self;
animation.fromValue = [NSNumber numberWithInt:0];
animation.toValue   = [NSNumber numberWithInt:255];
[self.character addAnimation:animation forKey:@"blue"];

此症状表示什么？如何为 NSAttributedString 属性设置动画？

What does this symptom imply? How do I animate NSAttributedString attributes?

推荐答案

这是一个简单的问题-（id）initWithLayer：（id）layer 方法的实现，因为一旦动画开始就调用它。

This was a simple question of implementing the - (id)initWithLayer:(id)layer method, because it gets called once the animation begins.

- (id)initWithLayer:(id)layer
{
    Character *temp = (Character *)layer;
    self = [super initWithLayer:layer];
    if (self) {
        self.symbol = temp.symbol;
        self.red    = temp.red;
        self.green  = temp.green;
        self.blue   = temp.blue;
    }
    return self;
}

现在这些属性结转，结果如预期。

Now the properties carry over and the results are as expected.

这篇关于动画NSMutableAttributedString颜色-字符串消失的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！