iOS WKWebView调用微信支付

业务场景为JS中调用微信支付，原生APP跳转至微信付款，成功或失败后返回原生APP。

1. 原生APP使用的为WKWebView，JS调用微信SDK后原生APP是不会跳转至微信的（UIWebView可以），需要在webView:decidePolicyForNavigationAction:decisionHandler:中添加代码

[[UIApplication sharedApplication] openURL:URL options:@{} completionHandler:nil];

此时原生APP可以跳转到微信了，但是付款成功或失败后并不能返回原生APP而是跳转到了safari，接下来就是为了让微信能够返回我们原生APP。

2. 当JS调用微信支付时我们在webView:decidePolicyForNavigationAction:decisionHandler:中会先后收到两波指令

• image1@2x.png
• image2.png

想让微信支付完成后跳回原生APP就需要处理https://wx.tenpay.com中的redirect_url，而weixin://wap/pay是真正调起微信的链接。
将第一条指令中redirect_url的值替换xxx.faker.com://www.myFaker.com/epay……，其中xxx.faker.com为申请微信支付时授权域名（问申请支付的开发人员，xxx可以随便是啥），同时在原生APP的URLType中添加xxx.faker.com

image3@2x.png

3. 这样微信支付完成跳转回原生APP后就会加载xxx.faker.com://www.myFaker.com/epay……，显然这个地址加载不出来（会空白页），还需将该地址的scheme替换为https
   最终代码为：

- (void)webView:(WKWebView *)webView decidePolicyForNavigationAction:(WKNavigationAction *)navigationAction decisionHandler:(void (^)(WKNavigationActionPolicy))decisionHandler {

    NSURLRequest *request = navigationAction.request;
    NSURL *URL = request.URL;
    NSString *myScheme = @"www.cmrh.com";
    if ([URL.host isEqualToString:@"wx.tenpay.com"]) {

        decisionHandler(WKNavigationActionPolicyAllow);
        NSURLComponents *cmps = [[NSURLComponents alloc] initWithURL:URL resolvingAgainstBaseURL:YES];
        NSString *redirect_url = nil;
        for (NSURLQueryItem *item in cmps.queryItems) {
            if ([item.name isEqualToString:@"redirect_url"]) {
                redirect_url = item.value;
                break;
            }
        }
        if (redirect_url == nil) return;
        NSURL *redirect_URL = [NSURL URLWithString:redirect_url];
        if (redirect_URL == nil) return;
        NSString *replaceScheme = redirect_URL.scheme;
        // 如果replaceScheme已经被替换过了就不再替换了
        if (replaceScheme == nil || [replaceScheme isEqualToString:myScheme]) return;
        NSString *my_redirect_url = [redirect_url stringByReplacingOccurrencesOfString:replaceScheme withString:myScheme];
        NSString *urlAbsoluteString = [URL.absoluteString stringByReplacingPercentEscapesUsingEncoding:(NSUTF8StringEncoding)];
        NSString *my_requestUrl = [urlAbsoluteString stringByReplacingOccurrencesOfString:redirect_url withString:my_redirect_url];
        NSURL *my_requestURL = [NSURL URLWithString:my_requestUrl];
        NSMutableURLRequest *my_request = [NSMutableURLRequest requestWithURL:my_requestURL];
        if (my_requestURL == nil) return;
        my_request.allHTTPHeaderFields = request.allHTTPHeaderFields;
        // 让webView加载被修改过的request
        // 这会导致本方法再次被调用哦
        [webView loadRequest:my_request];
        return;
    }

    if ([URL.scheme isEqualToString:@"weixin"]) {
        if ([[UIApplication sharedApplication] canOpenURL:URL]) {
            if (@available(iOS 10.0, *)) {
                [[UIApplication sharedApplication] openURL:URL options:@{} completionHandler:nil];
            } else {
                [[UIApplication sharedApplication] openURL:URL];
            }
            decisionHandler(WKNavigationActionPolicyCancel);
        }
    } else if ([URL.scheme isEqualToString:myScheme]) {
        // 在微信支付完成或失败后回到APP会调用
        // 将xxx.faker.com://www.myFaker.com/epay…
        // 修改成 https://www.myFaker.com/epay…
        // 让webView重新加载
        decisionHandler(WKNavigationActionPolicyCancel);
        NSString *urlAbsoluteString = [URL.absoluteString stringByReplacingPercentEscapesUsingEncoding:(NSUTF8StringEncoding)];
        NSString *schemeDetail = [NSString stringWithFormat:@"%@://",myScheme];
        NSString *targetUrl = [urlAbsoluteString stringByReplacingOccurrencesOfString:schemeDetail withString:@"https://"];
        NSURL *targetURL = [NSURL URLWithString:targetUrl];
        NSURLRequest *request = [NSURLRequest requestWithURL:targetURL];
        [webView loadRequest:request];
    } else {
        decisionHandler(WKNavigationActionPolicyAllow);
    }
}