iOS WKWebView添加类似微信的进度条

1.m中声明两个属性
@property (nonatomic, strong) WKWebView *wkWebView;
@property (nonatomic, strong) UIProgressView *progressView;
@property (nonatomic, assign) NSUInteger loadCount;
2.初始化方法自己写
.......
3.添加KVO

通过监听estimatedProgress可以获取它的加载进度 还可以监听它的title ,URL, loading
[wkWebView addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew context:nil];

4.计算进度条
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { 

    if ([keyPath isEqualToString:@"loading"]) {

    } else if ([keyPath isEqualToString:@"title"]) {
        self.title = self.wKWebView.title;
    } else if ([keyPath isEqualToString:@"URL"]) {    
    
    } else if ([keyPath isEqualToString:@"estimatedProgress"]) {
        
        self.progressView.progress = self.wKWebView.estimatedProgress;
    }
    
    if (object == self.wKWebView && [keyPath isEqualToString:@"estimatedProgress"]) {
        CGFloat newprogress = [[change objectForKey:NSKeyValueChangeNewKey] doubleValue];
        if (newprogress == 1) {
            self.progressView.hidden = YES;
            [self.progressView setProgress:0 animated:NO];
        }else {
            self.progressView.hidden = NO;
            [self.progressView setProgress:newprogress animated:YES];
        }
    }

}
 - (void)setLoadCount:(NSUInteger)loadCount {

   _loadCount = loadCount;

    if (loadCount == 0) {
        self.progressView.hidden = YES;
        [self.progressView setProgress:0 animated:NO];
    }else {
        self.progressView.hidden = NO;
        CGFloat oldP = self.progressView.progress;
        CGFloat newP = (1.0 - oldP) / (loadCount + 1) + oldP;
        if (newP > 0.95) {
            newP = 0.95;
        }
        [self.progressView setProgress:newP animated:YES];

    }
}

// 页面开始加载时调用
    - (void)webView:(WKWebView *)webView didStartProvisionalNavigation:(WKNavigation *)navigation {
    self.loadCount ++;

}

// 内容返回时
    - (void)webView:(WKWebView *)webView didCommitNavigation:(WKNavigation *)navigation {
    self.loadCount --;
    
}
//失败
    - (void)webView:(WKWebView *)webView didFailNavigation: (null_unspecified WKNavigation *)navigation withError:(NSError *)error {
    self.loadCount --;
    NSLog(@"%@",error);
}
//最后别忘记在dealloc 中取消监听