WKWebView 进度条

@property (nonatomic) WKWebView *webView;@property (nonatomic) CALayer *progresslayer;//创建webView之后监听estimatedProgress属性_webView = [[WKWebView alloc]initWithFrame:self.view.bounds];    //就是当前网页加载的进度，所以首先监听这个属性。-> estimatedProgress    [_webView addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew context:nil];    UIView *progress = [[UIView alloc]initWithFrame:CGRectMake(0, 64, CGRectGetWidth(self.view.frame), 3)];    progress.backgroundColor = [UIColor clearColor];    [self.view addSubview:progress];    //隐式动画    CALayer *layer = [CALayer layer];    layer.frame = CGRectMake(0, 0, 0, 3);    layer.backgroundColor = TEXTCOLOR.CGColor;    [progress.layer addSublayer:layer];    self.progresslayer = layer;//监听的方法- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context {    if ([keyPath isEqualToString:@"estimatedProgress"]) {        self.progresslayer.opacity = 1;        if ([change[@"new"] floatValue] < [change[@"old"] floatValue]) {            return;        }        self.progresslayer.frame = CGRectMake(0, 0, self.view.bounds.size.width * [change[@"new"] floatValue], 3);        if ([change[@"new"] floatValue] == 1) {            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(.4 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{                self.progresslayer.opacity = 0;            });            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{                self.progresslayer.frame = CGRectMake(0, 0, 0, 3);            });        }    } else {        [super observeValueForKeyPath:keyPath ofObject:object change:change context:context];    }}//移除监听- (void)dealloc {    [_webView removeObserver:self forKeyPath:@"estimatedProgress"];}