利用CoreAnimation实现一个时间的进度条

(个人原创，转载请注明出处 http://www.cnblogs.com/pretty-guy/p/7460334.html)

在iOS中实现进度条通常都是通过不停的设置progress来完成的，这样的进度条适用于网络加载（上传下载文件、图片等）。但是对于录制视频这样的需求的话，如果是按照每秒来设置进度的话，显得有点麻烦，于是我就想直接用CoreAnimation来按时间做动画，只要设置最大时间，其他的就不用管了，然后在视频暂停与继续录制时，对动画进行暂停和恢复即可。录制视频的效果如下：

你可以在这里下载demo

那么接下来就是如何用CoreAnimation实现一个进度条控件了。

首先呢，让我们创建一个继承自CAShapeLayer的WKProgressBarLayer。

WKProgressBarLayer默认自身的bounds就是整个进度条的大小。

@interface WKProgressBarLayer : CAShapeLayer

@end

为了方便外部调用，首先在WKProgressBarLayer.h中定义枚举来表明动画的四个状态

typedef NS_ENUM(NSInteger, WKAnimationStatus) {
    WKAnimationStatusIdle,//空闲
    WKAnimationStatusAnimating,//动画中
    WKAnimationStatusPause,//暂停
    WKAnimationStatusComplete//完成
};

接下来，定义外部调用的动画接口

@interface WKProgressBarLayer : CAShapeLayer

@property (nonatomic, assign, readonly) WKAnimationStatus animatingStatus;//状态

/**
 开始动画

 @param duration 动画最大时长
 */
- (void)beginAnimationWithDuration:(CGFloat)duration;

/**
 暂停
 */
- (void)pauseAnimation;

/**
 恢复
 */
- (void)resumeAnimation;

/**
 重新开始动画

 @param progress 从哪个进度开始
 @param duration 动画最大时长
 */
- (void)restartAnimationWithProgress:(CGFloat)progress duration:(NSTimeInterval)duration;
@end

然后，我们在.m实现核心的动画开始方法startAnimtionWithBeginProgress:duration:，详细解释见代码

- (void)startAnimtionWithBeginProgress:(CGFloat)beginProgress duration:(NSTimeInterval)duration
{
    [self reset];//重置动画
    //设置path
    UIBezierPath *fromPath = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, beginProgress * self.bounds.size.width, self.bounds.size.height)];;
    UIBezierPath *toPath = [UIBezierPath bezierPathWithRect:self.bounds];

    self.path = fromPath.CGPath;
    //创建动画
    CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:@"path"];
    animation.fromValue = (id)fromPath.CGPath;
    animation.toValue = (id)toPath.CGPath;
    animation.duration = duration;

    [animation setValue:@1 forKey:@"progress"];//用于判断是否是进度动画

    animation.delegate = self;  //用于判断动画结束
    [self addAnimation:animation forKey:@"progressAnimation"];

    self.path = toPath.CGPath;
}

然后呢，需要在动画的delegate与暂停、恢复动画的方法中分别修改动画的状态

- (void)pauseAnimation
{
    CFTimeInterval pausedTime = [self convertTime:CACurrentMediaTime() fromLayer:nil];
    self.speed = 0.0;
    self.timeOffset = pausedTime;
    self.animatingStatus = WKAnimationStatusPause;
}

- (void)resumeAnimation
{
    CFTimeInterval pausedTime = [self timeOffset];
    self.speed = 1.0;
    self.timeOffset = 0.0;
    self.beginTime = 0.0;
    CFTimeInterval timeSincePause = [self convertTime:CACurrentMediaTime() fromLayer:nil] - pausedTime;
    self.beginTime = timeSincePause;

    self.animatingStatus = WKAnimationStatusAnimating;
}

#pragma mark - CAAnimationDelegate
/* Called when the animation begins its active duration. */

- (void)animationDidStart:(CAAnimation *)anim
{
    if (anim == [self animationForKey:@"progressAnimation"]) {//判断进度动画
        self.animatingStatus = WKAnimationStatusAnimating;
    }
}

- (void)animationDidStop:(CAAnimation *)anim finished:(BOOL)flag
{
    if ([anim valueForKey:@"progress"] && flag == YES) {//判断进度动画
        self.animatingStatus = WKAnimationStatusComplete;
    }
}

至此，进度条layer就完成了，现在创建一个控制器来做测试

首先在storyBoard摆上两个按钮，分别是开始与重置动画(界面搭建很简单，详情见demo)

然后在ViewDidLoad中添加progressLayer

- (void)viewDidLoad {
    [super viewDidLoad];

    WKProgressBarLayer *progressLayer = [[WKProgressBarLayer alloc] init];
    progressLayer.frame = CGRectMake(100, 100, 200, 10);

    [self.view.layer addSublayer:progressLayer];

    self.progressLayer = progressLayer;
}

接下来，就是动画开始与重置响应

- (IBAction)startOrPauseAction:(UIButton *)sender {
        switch (self.progressLayer.animatingStatus) {
            case WKAnimationStatusIdle:{
                [self.progressLayer beginAnimationWithDuration:10];
            }

                break;
            case WKAnimationStatusAnimating:{
                [self.progressLayer pauseAnimation];
            }

                break;
            case WKAnimationStatusPause:{
                [self.progressLayer resumeAnimation];
            }

                break;
            case WKAnimationStatusComplete:{
                [self.progressLayer restartAnimationWithProgress:0 duration:10];
            }
                break;

            default:
                break;
    }
    sender.selected = !sender.selected;
}

- (IBAction)resetAction:(UIButton *)sender {
    [self.progressLayer restartAnimationWithProgress:0 duration:10];
    self.startOrPauseButton.selected = YES;
}

以上就是代码主体了，接下来，让我们看看效果

你可以在这里下载demo