Android Web-View : 将本地 Javascript 文件注入远程网页 [英] Android Web-View : Inject local Javascript file to Remote Webpage

问题描述

之前被问过很多次，我浏览了所有内容，还没有明确的答案.

It has been asked many times before, I browsed through everything, no clear answers yet.

问题简化:是否可以将本地 Javascript 文件(从资产或存储)注入到加载在 Android Web 视图中的远程网页?我知道可以将此类文件注入 Web 视图中加载的本地网页(资产 HTML).

Question simplified: Is it possible to inject local Javascript file (from asset or storage) to remote webpage loaded in an Android Web-View? I know that it is possible to inject such files to local Webpages (Assets HTML) loaded in a Web-View.

为什么我需要它来工作?:为了让浏览体验更快，避免每次下载较大的文件，如 Js 和 CSS 文件.我想避免 Web 视图缓存.

Why do I need this to work? : To make browsing experience faster, by avoiding downloading of bigger files such as Js and CSS files every time. I want to avoid Web-View Caching.

推荐答案

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，并规避不允许加载本地资源:file:///android_assets/js/script.js ..."问题.

There is a way to 'force' the injection of your local Javascript files from local assets (e.g., assets/js/script.js), and to circumvent the 'Not allowed to load local resource : file:///android_assets/js/script.js ...' issue.

它类似于另一个线程中描述的内容(Android webview，在 assets 文件夹中加载 javascript 文件)，附加的 BASE64 编码/解码用于将您的 Javascript 文件表示为可打印的字符串.

It is similar to what described in another thread (Android webview, loading javascript file in assets folder), with additional BASE64 encoding/decoding for representing your Javascript file as a printable string.

我使用的是 Android 4.4.2，API 级别 19 虚拟设备.

I am using an Android 4.4.2, API level 19 Virtual Device.

以下是一些代码片段:

[assets/js/script.js]:

[assets/js/script.js]:

    'use strict';

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

    // more Javascript

[MainActivity.java]:

[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");

    ...

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