Android Web-View:将本地Javascript文件注入远程网页

Question

之前已经多次询问过,我浏览了所有内容,还没有明确的答案.

问题简化:是否可以将本地Javascript文件(从资产或存储)注入Android Web视图中加载的远程网页？我知道可以将这些文件注入Web-View中加载的本地Web页面(Assets HTML).

为什么我需要这个呢？:通过避免每次都下载较大的文件(如Js和CSS文件)来提高浏览体验.我想避免Web-View缓存.

Answer 1

有一种方法可以"强制"从本地资产(例如,assets/js/script.js)注入本地Javascript文件,并绕过'不允许加载本地资源:file:/// android_assets/js /script.js ...'问题.

它类似于另一个线程(Android webview,在assets文件夹中加载javascript文件)中描述的内容,以及用于将Javascript文件表示为可打印字符串的附加BASE64编码/解码.

我使用的是Android 4.4.2,API级别19虚拟设备.

以下是一些代码段:

[资产/ JS /的script.js]:

    'use strict';

    function test() {
       // ... do something
    }

    // more Javascript

[MainActivity.java]:

    ...

    WebView myWebView = (WebView) findViewById(R.id.webView);
    WebSettings webSettings = myWebView.getSettings();

    webSettings.setJavaScriptEnabled(true);
    webSettings.setAllowUniversalAccessFromFileURLs(true);
    myWebView.setWebViewClient(new WebViewClient() {
       @Override
       public boolean shouldOverrideUrlLoading(WebView view, String url) {
          return false;
       }

       @Override
       public void onPageFinished(WebView view, String url) {
          super.onPageFinished(view, url);

          injectScriptFile(view, "js/script.js"); // see below ...

          // test if the script was loaded
          view.loadUrl("javascript:setTimeout(test(), 500)");
       }

       private void injectScriptFile(WebView view, String scriptFile) {
          InputStream input;
          try {
             input = getAssets().open(scriptFile);
             byte[] buffer = new byte[input.available()];
             input.read(buffer);
             input.close();

             // String-ify the script byte-array using BASE64 encoding !!!
             String encoded = Base64.encodeToString(buffer, Base64.NO_WRAP);
             view.loadUrl("javascript:(function() {" +
                          "var parent = document.getElementsByTagName('head').item(0);" +
                          "var script = document.createElement('script');" +
                          "script.type = 'text/javascript';" +
             // Tell the browser to BASE64-decode the string into your script !!!
                          "script.innerHTML = window.atob('" + encoded + "');" +
                          "parent.appendChild(script)" +
                          "})()");
          } catch (IOException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
          }
       }
    });

    myWebView.loadUrl("http://www.example.com");

    ...

Answer 2

是的,您可以使用shouldInterceptRequest()来拦截远程URL加载并返回本地存储的内容.

WebView webview = (WebView) findViewById(R.id.webview);

webview.setWebViewClient(new WebViewClient() {
    @Override
    public WebResourceResponse shouldInterceptRequest (final WebView view, String url) {
       if (url.equals("script_url_to_load_local")) {
           return new WebResourceResponse("text/javascript", "UTF-8", new FileInputStream("local_url")));
       } else {
           return super.shouldInterceptRequest(view, url);
       }
    }
});

Answer 3

loadUrl仅适用于旧版本使用evaluateJavascript

webview.evaluateJavascript("(function() { document.getElementsByName('username')[0].value='USERNAME';document.getElementsByName('password')[0].value='PASSWORD'; "+
"return { var1: \"variable1\", var2: \"variable2\" }; })();", new ValueCallback<String>() {
                @Override
                public void onReceiveValue(String s) {
                    Log.d("LogName", s); // Prints: {"var1":"variable1","var2":"variable2"}
                }
            });