Question

我有一个图层，在其drawInContext:中我使用drawInRect:绘制了一个属性字符串。这是我初始化图层的方式。

+ (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，因此我有三个动态属性。

@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，我设置了前景色。

/* 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];

角色会根据需要出现在屏幕上。但是，一旦我向图层添加CABasicAnimation，符号就会消失。

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"];

这种症状意味着什么？如何设置NSAttributedString属性的动画？

Answer 1

这是一个实现- (id)initWithLayer:(id)layer方法的简单问题，因为它会在动画开始后被调用。

- (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;
}

现在属性结转，结果如预期。

动画NSMutableAttributedString颜色 - 字符串消失

1 个答案: