js与OC互相调用 —— WKWebView拦截Url

首先介绍下WKWebview与UIWebview的区别，UIWebView自iOS2就有，WKWebView从iOS8才有，毫无疑问WKWebView将逐步取代笨重的UIWebView。通过简单的测试即可发现UIWebView占用过多内存，且内存峰值更是夸张。WKWebView网页加载速度也有提升，但是并不像内存那样提升那么多。下面列举一些其它的优势：

*   更多的支持HTML5的特性
*   官方宣称的高达60fps的滚动刷新率以及内置手势
*   Safari相同的JavaScript引擎
*   将UIWebViewDelegate与UIWebView拆分成了14类与3个协议([官方文档说明](https://developer.apple.com/library/mac/documentation/Cocoa/Reference/WebKit/ObjC_classic/index.html))
*   另外用的比较多的，增加加载进度属性：`estimatedProgress`

1.加载本地的Html文件，具体文件见上一篇文章附图
2.创建WKWebView

- (void)initWKWebView
{
    WKWebViewConfiguration *configuration = [[WKWebViewConfiguration alloc] init];
    configuration.userContentController = [WKUserContentController new];
    
    WKPreferences *preferences = [WKPreferences new];
    preferences.javaScriptCanOpenWindowsAutomatically = YES;
    preferences.minimumFontSize = 30.0;
    configuration.preferences = preferences;
    
    self.webView = [[WKWebView alloc] initWithFrame:self.view.frame configuration:configuration];
    NSString *urlStr = [[NSBundle mainBundle] pathForResource:@"index.html" ofType:nil];
    NSURL *fileURL = [NSURL fileURLWithPath:urlStr];
    [self.webView loadFileURL:fileURL allowingReadAccessToURL:fileURL];
    
    self.webView.navigationDelegate = self;
    self.webView.UIDelegate = self;
    [self.view addSubview:self.webView];
}

附属相关操作，创建进度条，监听estimatedProgress属性

    CGFloat kScreenWidth = [[UIScreen mainScreen] bounds].size.width;
    UIProgressView *progressView = [[UIProgressView alloc] initWithFrame:CGRectMake(0, 0, kScreenWidth, 2)];
    progressView.tintColor = [UIColor redColor];
    progressView.trackTintColor = [UIColor lightGrayColor];
    [self.view addSubview:progressView];
    self.progressView = progressView;

 [self.webView addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew context:nil]; // 监听网页加载进度

3.实现WKNavigationDelegate代理方法拦截Url
使用WKNavigationDelegate中的代理方法，拦截自定义的URL来实现JS调用OC方法

#pragma mark - WKNavigationDelegate
- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler
{
    NSURL *URL = navigationAction.request.URL;
    NSString *scheme = [URL scheme];
    if ([scheme isEqualToString:@"haleyaction"]) {
        
        [self handleCustomAction:URL];
        
        decisionHandler(WKNavigationActionPolicyCancel);
        return;
    }
    decisionHandler(WKNavigationActionPolicyAllow);
}

注意事项

1.如果实现了这个代理方法，就必须得调用decisionHandler这个block，否则会导致app 崩溃。block参数是个枚举类型，WKNavigationActionPolicyCancel代表取消加载，相当于UIWebView的代理方法return NO的情况；WKNavigationActionPolicyAllow代表允许加载，相当于UIWebView的代理方法中 return YES的情况。

方法区分，设置，和上一篇文章一样

#pragma mark - private method
- (void)handleCustomAction:(NSURL *)URL
{
    NSString *host = [URL host];
    if ([host isEqualToString:@"scanClick"]) {
        NSLog(@"扫一扫");
    } else if ([host isEqualToString:@"shareClick"]) {
        [self share:URL];
    } else if ([host isEqualToString:@"getLocation"]) {
        [self getLocation];
    } else if ([host isEqualToString:@"setColor"]) {
        [self changeBGColor:URL];
    } else if ([host isEqualToString:@"payAction"]) {
        [self payAction:URL];
    } else if ([host isEqualToString:@"shake"]) {
        [self shakeAction];
    } else if ([host isEqualToString:@"goBack"]) {
        [self goBack];
    }
  
}

调用JS方法，WKWebView 提供了一个新的方法evaluateJavaScript:completionHandler:，实现OC 调用JS 等场景。

// 将结果返回给js
    NSString *jsStr = [NSString stringWithFormat:@"setLocation('%@')",@"广东省深圳市南山区学府路XXXX号"];
    [self.webView evaluateJavaScript:jsStr completionHandler:^(id _Nullable result, NSError * _Nullable error) {
        NSLog(@"%@----%@",result, error);
    }];
   

附属监听estimatedProgress，在代理方法中实现

// 计算wkWebView进度条
- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context {
    if (object == self.webView && [keyPath isEqualToString:@"estimatedProgress"]) {
        CGFloat newprogress = [[change objectForKey:NSKeyValueChangeNewKey] doubleValue];
        if (newprogress == 1) {
            [self.progressView setProgress:1.0 animated:YES];
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.7 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                self.progressView.hidden = YES;
                [self.progressView setProgress:0 animated:NO];
            });
            
        }else {
            self.progressView.hidden = NO;
            [self.progressView setProgress:newprogress animated:YES];
        }
    }
}
// 释放时移除监听
- (void)dealloc
{
    NSLog(@"dealloc ---%s",__FUNCTION__);
    [self.webView removeObserver:self forKeyPath:@"estimatedProgress"];
}

4.WKWebView中使用弹窗
在WKWebView中使用alert、confirm 等弹窗，就得实现WKWebView的WKUIDelegate中相应的代理方法。
例如，我在JS中要显示alert 弹窗，就必须实现如下代理方法，否则alert 并不会弹出。

#pragma mark - WKUIDelegate
- (void)webView:(WKWebView *)webView runJavaScriptAlertPanelWithMessage:(NSString *)message initiatedByFrame:(WKFrameInfo *)frame completionHandler:(void (^)(void))completionHandler
{
    UIAlertController *alert = [UIAlertController alertControllerWithTitle:@"提醒" message:message preferredStyle:UIAlertControllerStyleAlert];
    [alert addAction:[UIAlertAction actionWithTitle:@"知道了" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        completionHandler();
    }]];

    [self presentViewController:alert animated:YES completion:nil];
}

html编写和相关方法调用区分，和上一篇文章大致相同，不多叙述。

以上文章实现了在WKWebview中实现JS和OC交互，并且使用了WKWebview中的estimatedProgress新属性，使用KVO监听，实现了基本的进度条功能。