UILabel混合显示动画效果

效果

源码

////  MixedColorProgressViewController.m//  Animations////  Created by YouXianMing on 16/1/5.//  Copyright © 2016年 YouXianMing. All rights reserved.//#import "MixedColorProgressViewController.h"#import "UIView+SetRect.h"#import "GCD.h"@interface MixedColorProgressViewController ()@property (nonatomic, strong)  UIView   *upView;@property (nonatomic, strong)  UILabel  *upLabel;@property (nonatomic, strong)  UIView   *downView;@property (nonatomic, strong)  UILabel  *downLabel;@property (nonatomic, strong)  GCDTimer *timer;@end@implementation MixedColorProgressViewController- (void)setup {    [super setup];        /*     给upView的frame值做动画才是label能够混色显示的核心          upView(红色背景)   ===>  upLabel(白色底字)     |                       |     |                       |     |                       |     |                       |     downView(白色背景) ===> downLabel(红色底字)          */        // 上面一层    {        // 红色背景        _upView                     = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 220, 17)];        _upView.center              = self.view.center;        _upView.layer.cornerRadius  = 2.f;        _upView.backgroundColor     = [UIColor redColor];        _upView.layer.masksToBounds = YES; // 核心(不让subview显示超出范围)        [self.view addSubview:_upView];                // 白色底字        _upLabel                    = [[UILabel alloc] initWithFrame:_upView.bounds];        _upLabel.font               = [UIFont fontWithName:@"HelveticaNeue-Thin" size:13];        _upLabel.text               = @"YouXianMing - iOS Programmer";        _upLabel.textColor          = [UIColor whiteColor];        _upLabel.textAlignment      = NSTextAlignmentCenter;        [_upView addSubview:_upLabel];    }        // 下面一层    {        // 白色背景        _downView                     = [[UIView alloc] initWithFrame:CGRectMake(0, 0, 220, 17)];        _downView.center              = self.view.center;        _downView.layer.cornerRadius  = 2.f;        _downView.backgroundColor     = [UIColor whiteColor];        [self.view addSubview:_downView];                // 红色底字        _downLabel                    = [[UILabel alloc] initWithFrame:_downView.bounds];        _downLabel.textColor          = [UIColor redColor];        _downLabel.font               = [UIFont fontWithName:@"HelveticaNeue-Thin" size:13];        _downLabel.text               = @"YouXianMing - iOS Programmer";        _downLabel.textAlignment = NSTextAlignmentCenter;        [_downView addSubview:_downLabel];    }        // 显示上面一层    [self.view bringSubviewToFront:_upView];        // 给上面一层的frame值做动画    _timer = [[GCDTimer alloc] initInQueue:[GCDQueue mainQueue]];    [_timer event:^{                [UIView animateWithDuration:0.5f delay:0.f usingSpringWithDamping:3.f initialSpringVelocity:0 options:0 animations:^{                        _upView.width = arc4random() % 220;                    } completion:nil];            } timeInterval:NSEC_PER_SEC];    [_timer start];}@end

细节