iOS WKWebView添加进度条02

之前写了一个是关于webview添加进度条的，现在补一个WKWebView进度条。
//添加一个全局属性
@property(nonatomic,strong)CALayer *progresslayer;

//viewDidLoad里添加监听
[_webViewaddObserver:selfforKeyPath:@"estimatedProgress"options:NSKeyValueObservingOptionNewcontext:nil];

//进度条
UIView *progress = [[UIView alloc]initWithFrame:CGRectMake(0, 0, CGRectGetWidth(self.view.frame), 3)];
progress.backgroundColor = [UIColor clearColor];
[self.view addSubview:progress];

CALayer *layer = [CALayer layer];
layer.frame = CGRectMake(0, 0, 0, 3);
layer.backgroundColor = [UIColor greenColor].CGColor;
[progress.layer addSublayer:layer];

self.progresslayer = layer;

- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSString *,id> *)change context:(void *)context{

if ([keyPath isEqualToString:@"estimatedProgress"]) {
self.progresslayer.opacity = 1;
//不要让进度条倒着走...有时候goback会出现这种情况
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)viewWillDisappear:(BOOL)animated{
[super viewWillDisappear:animated];
[_webView removeObserver:self forKeyPath:@"estimatedProgress"];

}