cordova allow-navigation、allow-intent 解析

cordova 项目的配置文件 config.xml 里有 allow-navigation 和 allow-intent 两个配置。用途如下：

allow-navigation

控制哪些URL由 WebView 打开(Controls which URLs the WebView itself can be navigated to. Applies to top-level navigations only.)。
如果想让Cordova的WebView能打开https://www.google.com，那么需要在config.xml里加上如下配置

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<allow-navigation href="https://www.google.com" />
...

allow-intent

控制哪些URL让系统去打开(Controls which URLs the app is allowed to ask the system to open.)。
比如 sms:*、tel:*、itms-services:* 等，这些可以让系统去打开。也可以让系统打开 http:*、https:* 的链接，这时系统会调用系统浏览器打开

allow-navigation 优先级比 allow-intent 高，比如 allow-navigation 没配置 https://www.google.com， 而 allow-intent 配置了，那么就会调用系统浏览器打开链接

注意事项

最好不要像这样配置

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<allow-navigation href="*" />
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可以先猜想会发生什么？

思考中…
思考中…
思考中…

如果像上面那样配置，那么 sms:*、tel:*、itms-services:* 这些 scheme 的URL都被 WebView 拦截了，而 WebView 默认其实只能处理 http、https、file、data 这些 scheme（可能还有其他的） 的URL，所以上面那些 scheme 无法打开，一般会报下面错误

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Failed to load webpage with error: unsupported URL

我自己就犯了这个错误，加了 <allow-navigation href="*" /> 配置，然后调用 window.location.href=itms-services://?action=download-manifest&url=https:xxxxxx.plist 去下载应用，结果一直报 加载失败 错误，所以在这里记录下。

源码

Cordova 里处理这个过滤逻辑的源码主要在 CDVIntentAndNavigationFilter 这个类里，核心代码如下

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+ (CDVIntentAndNavigationFilterValue) filterUrl:(NSURL*)url intentsWhitelist:(CDVWhitelist*)intentsWhitelist navigationsWhitelist:(CDVWhitelist*)navigationsWhitelist
{
    // a URL can only allow-intent OR allow-navigation, if both are specified,
    // only allow-navigation is allowed
    
    BOOL allowNavigationsPass = [navigationsWhitelist URLIsAllowed:url logFailure:NO];
    BOOL allowIntentPass = [intentsWhitelist URLIsAllowed:url logFailure:NO];
    
    if (allowNavigationsPass && allowIntentPass) {
        return CDVIntentAndNavigationFilterValueNavigationAllowed;
    } else if (allowNavigationsPass) {
        return CDVIntentAndNavigationFilterValueNavigationAllowed;
    } else if (allowIntentPass) {
        return CDVIntentAndNavigationFilterValueIntentAllowed;
    }
    
    return CDVIntentAndNavigationFilterValueNoneAllowed;
}

+ (BOOL)shouldOverrideLoadWithRequest:(NSURLRequest*)request navigationType:(UIWebViewNavigationType)navigationType filterValue:(CDVIntentAndNavigationFilterValue)filterValue
{
    NSString* allowIntents_whitelistRejectionFormatString = @"ERROR External navigation rejected - <allow-intent> not set for url='%@'";
    NSString* allowNavigations_whitelistRejectionFormatString = @"ERROR Internal navigation rejected - <allow-navigation> not set for url='%@'";
    
    NSURL* url = [request URL];
    
    switch (filterValue) {
        case CDVIntentAndNavigationFilterValueNavigationAllowed:
            return YES;
        case CDVIntentAndNavigationFilterValueIntentAllowed:
            // only allow-intent if it's a UIWebViewNavigationTypeLinkClicked (anchor tag) OR
            // it's a UIWebViewNavigationTypeOther, and it's an internal link
            if ([[self class] shouldOpenURLRequest:request navigationType:navigationType]){
                [[UIApplication sharedApplication] openURL:url options:@{} completionHandler:nil];
            }
            
            // consume the request (i.e. no error) if it wasn't handled above
            return NO;
        case CDVIntentAndNavigationFilterValueNoneAllowed:
            // allow-navigation attempt failed for sure
            NSLog(@"%@", [NSString stringWithFormat:allowNavigations_whitelistRejectionFormatString, [url absoluteString]]);
            // anchor tag link means it was an allow-intent attempt that failed as well
            if (UIWebViewNavigationTypeLinkClicked == navigationType) {
                NSLog(@"%@", [NSString stringWithFormat:allowIntents_whitelistRejectionFormatString, [url absoluteString]]);
            }
            return NO;
    }
}

结语

由于自己犯下的这个错误导致某版本用户无法正常升级，因此学习下cordova相应源码，在此记录（吃一堑长一智）。也希望有缘人看的这篇文章能规避相应错误。