iOS实现一个高性能的跑马灯

效果图

该跑马灯完全通过CATextLayer 实现，轻量级，并且通过
系统的位移动画实现滚动效果，避免了使用displaylink造成的性能瓶颈，使用系统动画，系统自动做了很多性能优化，实现更好的性能，并使用遮罩实现展示范围的限定
，实现跑马灯效果

//
//  LBMarqueeLayer.m
//  TEXT
//
//  Created by mac on 2024/4/28.
//  Copyright © 2024 刘博. All rights reserved.
//

#import "LBMarqueeLayer.h"

@implementation LBMarqueeLayerConfig

- (instancetype)init
{
    self = [super init];
    if (self) {
        self.velocity = 20;
        self.fontSize = 14;
        self.textColor = [UIColor darkGrayColor];
        self.pauseDuration = 3;
        self.blankString = @"  ";
    }
    return self;
}

@end

@interface LBMarqueeLayer () <CAAnimationDelegate>

@property (nonatomic, strong) CATextLayer *textLayer;

@property (nonatomic, strong) CALayer *maskLayer;

@property (nonatomic, strong) LBMarqueeLayerConfig *config;

@property (nonatomic, strong) CABasicAnimation *animation;

@end

@implementation LBMarqueeLayer

- (instancetype)initwithFrame:(CGRect)frame
                       config:(LBMarqueeLayerConfig *)config
{
    if ([super init]) {
        self.frame = frame;
        self.config = config;
        [self handleText];
        [self addSublayer:self.textLayer];
    }
    return self;
}

- (void)handleText
{
    CGFloat width = [self.config.text sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:self.config
                                                                                .fontSize]}].width;
    if (width > CGRectGetWidth(self.bounds)) {
        NSString *content = [NSString stringWithFormat:@"%@%@%@", self.config.text, self.config.blankString, self.config.text];
        NSAttributedString *attributedString = [[NSAttributedString alloc] initWithString:content attributes:@{NSFontAttributeName:[UIFont systemFontOfSize:self.config.fontSize]}];
        self.textLayer.string = attributedString;
        CGFloat width = [content sizeWithAttributes:@{NSFontAttributeName: [UIFont systemFontOfSize:self.config
                                                                            .fontSize]}].width;
        self.textLayer.frame = CGRectMake(0, 0, width, CGRectGetHeight(self.bounds));
        CGFloat toValue = [[NSString stringWithFormat:@"%@%@", self.config.text, self.config.blankString] sizeWithAttributes:@{NSFontAttributeName:[UIFont systemFontOfSize:self.config
                                                                                                                            .fontSize]}].width;
        self.animation.fromValue = @(0);
        self.animation.toValue = @(-toValue);
        self.animation.duration = toValue/self.config.velocity;
        [self.textLayer addAnimation:self.animation forKey:@"animation"];
        self.masksToBounds = YES;
        } else {
            self.textLayer.string = self.config.text;
        }
    }
    
#pragma mark - animationDelegate
    
    - (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
    {
        
        if (flag) {
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(self.config.pauseDuration * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                [self.textLayer addAnimation:self.animation forKey:@"animation"];
            });
        }
    }
    
#pragma mark - lazy load
    
    - (CATextLayer *)textLayer
    {
        if (!_textLayer) {
            _textLayer = [[CATextLayer alloc] init];
            _textLayer.frame = CGRectMake(0, 0, CGRectGetWidth(self.frame), CGRectGetHeight(self.frame));
            _textLayer.alignmentMode = kCAAlignmentLeft;
            _textLayer.fontSize = 14;
            _textLayer.foregroundColor = self.config.textColor.CGColor;
        }
        return _textLayer;
    }
    
    - (CALayer *)maskLayer
    {
        if (!_maskLayer) {
            _maskLayer = [[CALayer alloc] init];
            _maskLayer.frame = self.bounds;
        }
        return _maskLayer;
    }
    
    - (CABasicAnimation *)animation
    {
        if (!_animation) {
            _animation = [CABasicAnimation animationWithKeyPath:@"transform.translation.x"];
            if (!self.config.hasPause) {
                _animation.repeatCount = NSIntegerMax;
            }
            _animation.delegate = self;
        }
        return _animation;
    }
    
    @end

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调用

- (LBMarqueeLayer *)textLayer
{
    if (!_textLayer) {
        LBMarqueeLayerConfig *config = [[LBMarqueeLayerConfig alloc] init];
        config.hasPause = YES;
        config.pauseDuration = 3;
        config.blankString = @"      ";
        config.text = @"这是一首非常好听的歌曲哈哈哈哈";
        _textLayer = [[LBMarqueeLayer alloc] initwithFrame:CGRectMake(100, 100, 200, 50) config:config];
        _textLayer.backgroundColor = [UIColor cyanColor].CGColor;
    }
    return _textLayer;
}

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