WKWebview的基本使用

在开发过程中，iOS 中实现加载 web 页面主要有两种控件，UIWebView 和 WKWebview，两种控件对应具体的实现方法不同。WKWebView是苹果公司在iOS8系统推出的，这里主要概述WebKit中更新的WKWebView控件的新特性与使用方法，以及小编在开发过程中踩的坑。

一、相比于UIWebView的优势：

1. 在性能、稳定性、占用内存方面有很大提升；
2. 允许JavaScript的Nitro库加载并使用（UIWebView中限制）
3. 增加加载进度属性：estimatedProgress，不用在自己写假进度条了
4. 支持了更多的HTML的属性

二、WKWebview的常用属性

@property (nullable, nonatomic, readonly, copy) NSString *title;

@property (nullable, nonatomic, readonly, copy) NSURL *URL;

@property (nonatomic, readonly, getter=isLoading) BOOL loading;
//加载进度
@property (nonatomic, readonly) double estimatedProgress;

三、WKWebview的常用方法

- (nullable WKNavigation *)loadRequest:(NSURLRequest *)request;

- (nullable WKNavigation *)loadFileURL:(NSURL *)URL allowingReadAccessToURL:(NSURL *)readAccessURL API_AVAILABLE(macosx(10.11), ios(9.0));

- (nullable WKNavigation *)loadHTMLString:(NSString *)string baseURL:(nullable NSURL *)baseURL;

- (nullable WKNavigation *)loadData:(NSData *)data MIMEType:(NSString *)MIMEType characterEncodingName:(NSString *)characterEncodingName baseURL:(NSURL *)baseURL API_AVAILABLE(macosx(10.11), ios(9.0));

四、WKNavigationDelegate代理的方法

#pragma mark - WKNavigationDelegate
/* 页面开始加载 */
- (void)webView:(WKWebView *)webView didStartProvisionalNavigation:(WKNavigation *)navigation{
    NSLog(@"页面开始加载");
}
/* 开始返回内容 */
- (void)webView:(WKWebView *)webView didCommitNavigation:(WKNavigation *)navigation{
    NSLog(@"开始返回内容");
}
/* 页面加载完成 */
- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation{
    NSLog(@"页面加载完成");
}
/* 页面加载失败 */
- (void)webView:(WKWebView *)webView didFailProvisionalNavigation:(WKNavigation *)navigation{
    NSLog(@"页面加载失败");
}
/* 在发送请求之前，决定是否跳转 */
- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler{
    //允许跳转
    decisionHandler(WKNavigationActionPolicyAllow);
    //不允许跳转
    //decisionHandler(WKNavigationActionPolicyCancel);
}
/* 在收到响应后，决定是否跳转 */
- (void)webView:(WKWebView *)webView decidePolicyForNavigationResponse:(WKNavigationResponse *)navigationResponse decisionHandler:(void (^)(WKNavigationResponsePolicy))decisionHandler{
    
    NSLog(@"%@",navigationResponse.response.URL.absoluteString);
    //允许跳转
    decisionHandler(WKNavigationResponsePolicyAllow);
    //不允许跳转
    //decisionHandler(WKNavigationResponsePolicyCancel);
}

五、小编的实例Demo

首先遵守协议：

<WKUIDelegate, WKNavigationDelegate>

其次创建一个WKWebView

#pragma mark - 创建webView
- (void)createWebView{
    
    WKWebViewConfiguration *config = [[WKWebViewConfiguration alloc] init];
    config.selectionGranularity = WKSelectionGranularityDynamic;
    config.allowsInlineMediaPlayback = YES;
    WKPreferences *preferences = [WKPreferences new];
    //是否支持JavaScript
    preferences.javaScriptEnabled = YES;
    //不通过用户交互，是否可以打开窗口
    preferences.javaScriptCanOpenWindowsAutomatically = YES;
    config.preferences = preferences;
    self.webView = [[WKWebView alloc] initWithFrame:self.view.bounds];
    [self.view addSubview:self.webView];
    
    /* 加载服务器url的方法*/
    NSString *url = @"https://www.baidu.com";
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
    [self.webView loadRequest:request];
    
    self.webView.navigationDelegate = self;
    self.webView.UIDelegate = self;

}

这样就可以在webView中正常加载百度首页了。

不过，在开发中有时遇到网络不佳的时候，想给用户显示一个加载网页的进度，加载完成后，想再navigation中显示网页的标题，就需要对WKWebView的"estimatedProgress"和

"title"进行监听了。

首先创建一个进度条

- (void)createProgressView{
    self.progressView = [[UIProgressView alloc] initWithFrame:CGRectMake(0, 88, SCREEN_WIDTH, 2)];
    self.progressView.progressViewStyle = UIProgressViewStyleDefault;
    self.progressView.tintColor = [UIColor blueColor];
    self.progressView.trackTintColor = [UIColor greenColor];
    [self.view addSubview:self.progressView];
}

让webView对“进度”和“标题”进行监听

[self.webView addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew context:nil];
[self.webView addObserver:self forKeyPath:@"title" options:NSKeyValueObservingOptionNew context:NULL];

最后，完成对KVO的回调

#pragma mark - KVO回馈
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context{
    if ([keyPath isEqualToString:@"estimatedProgress"]) {
        double progress = _webView.estimatedProgress;
        self.progressView.alpha = 1.0f;
        [self.progressView setProgress:progress animated:YES];
        if(progress >= 1){
            [UIView animateWithDuration:0.25 delay:0.25 options:UIViewAnimationOptionCurveEaseOut animations:^{
                self.progressView.alpha = 0.0f;
            } completion:^(BOOL finished) {
                [self.progressView setProgress:0.0f animated:NO];
            }];
        }
        if ([change[@"new"] floatValue] <[change[@"old"] floatValue]) {
            return;
        }
        if ([change[@"new"]floatValue] == 1.0) {
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                
            });
        }
    }
    else if ([keyPath isEqualToString:@"title"]){
        self.title = change[@"new"];
    }
}

这样就实现了对加载进度的显示了。