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WKWebView在实际开发中的使用汇总

2018-03-12 17:09 出处:清屏网 人气: 评论(0

最近公司的项目中大量使用了webview加载H5,鉴于WKWebView的性能优于UIWebView,所以就选择了WKWebView。WKWebView在使用的过程中,还是有很过内容值得我们去记录和研究的,这里我就做了一下总结,跟大家分享一下。

一、基本使用

WKWebView的基本使用网上也有很多,这里我就简略的写一下:

引入头文件 #import <WebKit/WebKit.h>

- (void)setupWebview{
    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;

    WKWebView *webview = [[WKWebView alloc] initWithFrame:CGRectMake(0, 0, KScreenWidth, KScreenHeight - 64) configuration:config];
    [self.view addSubview:webview];
    
    /* 加载服务器url的方法*/
    NSString *url = @"https://www.baidu.com";
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:url]];
    [webview loadRequest:request];
    
    webview.navigationDelegate = self;
    webview.UIDelegate = self;
}

WKWebViewConfiguration和WKPreferences中有很多属性可以对webview初始化进行设置,这里就不一一介绍了。

遵循的协议和实现的协议方法:

#pragma mark - WKNavigationDelegate
/* 页面开始加载 */
- (void)webView:(WKWebView *)webView didStartProvisionalNavigation:(WKNavigation *)navigation{

}
/* 开始返回内容 */
- (void)webView:(WKWebView *)webView didCommitNavigation:(WKNavigation *)navigation{
    
}
/* 页面加载完成 */
- (void)webView:(WKWebView *)webView didFinishNavigation:(WKNavigation *)navigation{
    
}
/* 页面加载失败 */
- (void)webView:(WKWebView *)webView didFailProvisionalNavigation:(WKNavigation *)navigation{
    
}
/* 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);
}

下面介绍几个开发中需要实现的小细节:

1、url中文处理

有时候我们加载的URL中可能会出现中文,需要我们手动进行转码,但是同时又要保证URL中的特殊字符保持不变,那么我们就可以使用下面的方法(方法放到了NSString中的分类中):

- (NSURL *)url{
#pragma clang diagnostic push
#pragma clang diagnostic ignored"-Wdeprecated-declarations"
    return [NSURL URLWithString:(NSString *)CFBridgingRelease(CFURLCreateStringByAddingPercentEscapes(kCFAllocatorDefault, (CFStringRef)self, (CFStringRef)@"!$&'()*+,-./:;=?@_~%#[]", NULL,kCFStringEncodingUTF8))];
#pragma clang diagnostic pop
}

2、获取h5中的标题 3、添加进度条

获取h5中的标题和添加进度条放到一起展示看起来更明朗一点,在初始化wenview时,添加两个观察者分别用来监听webview 的 estimatedProgresstitle 属性:

webview.navigationDelegate = self;
webview.UIDelegate = self;
    
[webview addObserver:self forKeyPath:@"estimatedProgress" options:NSKeyValueObservingOptionNew context:nil];
[webview addObserver:self forKeyPath:@"title" options:NSKeyValueObservingOptionNew context:NULL];

添加创建进度条,并添加进度条图层属性:

@property (nonatomic,weak) CALayer *progressLayer;
-(void)setupProgress{
    UIView *progress = [[UIView alloc]init];
    progress.frame = CGRectMake(0, 0, KScreenWidth, 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;
}

实现观察者的回调方法:

#pragma mark - KVO回馈
-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,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, KScreenWidth*[change[@"new"] floatValue], 3);
        if ([change[@"new"]floatValue] == 1.0) {
            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(.5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
                self.progressLayer.opacity = 0;
                self.progressLayer.frame = CGRectMake(0, 0, 0, 3);
            });
        }
    }else if ([keyPath isEqualToString:@"title"]){
        self.title = change[@"new"];
    }
}

下面是实现的效果图:

效果图-1.gif

4、添加userAgent信息

有时候H5的伙伴需要我们为webview的请求添加userAgent,以用来识别操作系统等一下信息,但是如果每次用到webview都要添加一次的话会比较麻烦,下面介绍一个一劳永逸的方法。

在Appdelegate中添加一个WKWebview的属性,启动app时直接,为该属性添加userAgent:

- (void)setUserAgent {
    _webView = [[WKWebView alloc] initWithFrame:CGRectZero];
    [_webView evaluateJavaScript:@"navigator.userAgent" completionHandler:^(id result, NSError *error) {
        if (error) { return; }
        NSString *userAgent = result;
        if (![userAgent containsString:@"/mobile-iOS"]) {
            userAgent = [userAgent stringByAppendingString:@"/mobile-iOS"];
            NSDictionary *dict = @{@"UserAgent": userAgent};
            [TKUserDefaults registerDefaults:dict];
        }
    }];
}

这样一来,在app中创建的webview都会存在我们添加的userAgent的信息。

二、原生JS交互

(一)JS调用原生方法

在WKWebView中实现与JS的交互还需要实现另外一个代理方法: WKScriptMessageHandler

#pragma mark - WKScriptMessageHandler
- (void)userContentController:(WKUserContentController *)userContentController
      didReceiveScriptMessage:(WKScriptMessage *)message

messagenamebody 属性中我们可以获取到与JS调取原生的方法名和所传递的参数。

(二)原生调用JS方法

[webview evaluateJavaScript:“JS语句” completionHandler:^(id _Nullable data, NSError * _Nullable error) {
       
 }];

下面举例说明:

实现H5通过原生方法调用相册

首先,遵循代理:

<WKNavigationDelegate, WKUIDelegate,WKScriptMessageHandler>

注册方法名:

config.preferences = preferences;

WKUserContentController *user = [[WKUserContentController alloc]init];
[user addScriptMessageHandler:self name:@"takePicturesByNative"];
config.userContentController =user;

实现代理方法:

#pragma mark - WKScriptMessageHandler
- (void)userContentController:(WKUserContentController *)userContentController
      didReceiveScriptMessage:(WKScriptMessage *)message{
    if ([message.name isEqualToString:@"takePicturesByNative"]) {
       [self takePicturesByNative];
    }
}
- (void)takePicturesByNative{
    UIImagePickerController *vc = [[UIImagePickerController alloc] init];
    vc.delegate = self;
    vc.sourceType = UIImagePickerControllerSourceTypePhotoLibrary;
    
    [self presentViewController:vc animated:YES completion:nil];
}
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary<NSString *,id> *)info {
    NSTimeInterval timeInterval = [[NSDate date]timeIntervalSince1970];
    NSString *timeString = [NSString stringWithFormat:@"%.0f",timeInterval];
    
    UIImage *image = [info  objectForKey:UIImagePickerControllerOriginalImage];
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);
    NSString *filePath = [[paths objectAtIndex:0] stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.png",timeString]];  //保存到本地
    [UIImagePNGRepresentation(image) writeToFile:filePath atomically:YES];
    NSString *str = [NSString stringWithFormat:@"%@",filePath];
    [picker dismissViewControllerAnimated:YES completion:^{
        // oc 调用js 并且传递图片路径参数
        [self.webview evaluateJavaScript:[NSString stringWithFormat:@"getImg('%@')",str] completionHandler:^(id _Nullable data, NSError * _Nullable error) {
        }];

    }];
}

我们期望的效果是,点击webview中 打开相册 的按钮,调用原生方法,展示相册,选择图片,可以传递给JS,并展示在webview中。

但是运行程序发现:我们可以打开相册,说明JS调用原生方法成功了,但是并不能在webview中展示出来,说明原生调用JS方法时,出现了问题。这是因为,在WKWebView中,H5在加载本地的资源(包括图片、CSS文件、JS文件等等)时,默认被禁止了,所以根据我们传递给H5的图片路径,无法展示图片。解决办法:在传递给H5的图片路径中添加我们自己的请求头,拦截H5加载资源的请求头进行判断,拿到路径然后由我们来手动请求。

先为图片路径添加一个我们自己的请求头:

NSString *str = [NSString stringWithFormat:@"myapp://%@",filePath];

然后创建一个新类继承于 NSURLProtocol

.h

#import <UIKit/UIKit.h>
@interface MyCustomURLProtocol : NSURLProtocol
@end

.m

@implementation MyCustomURLProtocol
+ (BOOL)canInitWithRequest:(NSURLRequest*)theRequest{
    if ([theRequest.URL.scheme caseInsensitiveCompare:@"myapp"] == NSOrderedSame) {
        return YES;
    }
    return NO;
}

+ (NSURLRequest*)canonicalRequestForRequest:(NSURLRequest*)theRequest{
    return theRequest;
}

- (void)startLoading{
    NSURLResponse *response = [[NSURLResponse alloc] initWithURL:[self.request URL]
                                                        MIMEType:@"image/png"
                                           expectedContentLength:-1
                                                textEncodingName:nil];
    NSString *imagePath = [self.request.URL.absoluteString componentsSeparatedByString:@"myapp://"].lastObject;
    NSData *data = [NSData dataWithContentsOfFile:imagePath];
    [[self client] URLProtocol:self didReceiveResponse:response cacheStoragePolicy:NSURLCacheStorageNotAllowed];
    [[self client] URLProtocol:self didLoadData:data];
    [[self client] URLProtocolDidFinishLoading:self];
}
- (void)stopLoading{
}
@end

在控制器中注册MyCustomURLProtocol协议并添加对myapp协议的监听:

//注册
    [NSURLProtocol registerClass:[MyCustomURLProtocol class]];
    //实现拦截功能
    Class cls = NSClassFromString(@"WKBrowsingContextController");
    SEL sel = NSSelectorFromString(@"registerSchemeForCustomProtocol:");
    if ([(id)cls respondsToSelector:sel]) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
        [(id)cls performSelector:sel withObject:@"myapp"];
#pragma clang diagnostic pop
    }

运行程序,效果如下:

效果图-2.gif

不仅仅是加载本地的图片,webview加载任何本地的资源都可以使用该方法,不过在使用过程中,大家一定要密切注意跨域问题会带来的安全性问题。

结尾

关于WKWebView其实还有很多内容,接下来我还会继续深入地去探究WKWebView的原理和使用。

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