WebView 笔记

Android WebView的几个核心类（framework源码）：

WebView 视图
WebViewClient WebView的回调类

WebViewProvider WebView的接口类

WebViewCore WebView核心类，持有 CallbackProxy 实例，通过mCallbackProxy回调到CallbackProxy
        WebCoreThread Web线程类
        EventHub

BrowserFrame -- Handler
CallbackProxy -- Handler

 

WebBackForwardList

web主框架加载栈（后退/前进列表），内部维护一个ArrayList<WebHistoryItem>

持有CallbackProxy，当列表增加、减少或当前索引改变时，进行回调

WebBackForwardList.setClearPending() 将后退/前进列表标记为具有挂起清除

WebView.loadUrl() 代码

1.  
   public void loadUrl(String url) {
2.  
   checkThread();
3.  
   loadUrlImpl(url);
4.  
   }
5.  
    
6.  
   private void loadUrlImpl(String url) {
7.  
   if (url == null) {
8.  
   return;
9.  
   }
10.  
    loadUrlImpl(url, null);
11.  
    }
12.  
     
13.  
    public void loadUrl(String url, Map<String, String> additionalHttpHeaders) {
14.  
    checkThread();
15.  
    loadUrlImpl(url, additionalHttpHeaders);
16.  
    }
17.  
     
18.  
    private void loadUrlImpl(String url, Map<String, String> extraHeaders) {
19.  
    switchOutDrawHistory();
20.  
    WebViewCore.GetUrlData arg = new WebViewCore.GetUrlData();
21.  
    arg.mUrl = url;
22.  
    arg.mExtraHeaders = extraHeaders;
23.  
    mWebViewCore.sendMessage(EventHub.LOAD_URL, arg);
24.  
    clearHelpers();
25.  
    }

WebViewCore中Handler的handleMessage：

1.  
   @Override
2.  
   public void handleMessage(Message msg) {
3.  
   ...
4.  
   case LOAD_URL: {
5.  
   CookieManager.getInstance().waitForCookieOperationsToComplete();
6.  
   GetUrlData param = (GetUrlData) msg.obj;
7.  
   loadUrl(param.mUrl, param.mExtraHeaders);
8.  
   break;
9.  
   }
10.  
    ...
11.  
    }
12.  
     
13.  
    private void loadUrl(String url, Map<String, String> extraHeaders) {
14.  
    if (DebugFlags.WEB_VIEW_CORE) Log.v(LOGTAG, " CORE loadUrl " url);
15.  
    mBrowserFrame.loadUrl(url, extraHeaders);
16.  
    }
17.  
    }

BrowserFrame中的loadUrl

1.  
   /**
2.  
   * Load a url from the network or the filesystem into the main frame.
3.  
   * Following the same behaviour as Safari, javascript: URLs are not passed
4.  
   * to the main frame, instead they are evaluated immediately.
5.  
   * @param url The url to load.
6.  
   * @param extraHeaders The extra headers sent with this url. This should not
7.  
   * include the common headers like "user-agent". If it does, it
8.  
   * will be replaced by the intrinsic value of the WebView.
9.  
   */
10.  
    public void loadUrl(String url, Map<String, String> extraHeaders) {
11.  
    mLoadInitFromJava = true;
12.  
    if (URLUtil.isJavaScriptUrl(url)) {
13.  
    // strip off the scheme and evaluate the string
14.  
    stringByEvaluatingJavaScriptFromString(
15.  
    url.substring("javascript:".length()));
16.  
    } else {
17.  
    nativeLoadUrl(url, extraHeaders);
18.  
    }
19.  
    mLoadInitFromJava = false;
20.  
    }

loadUrl中直接调用native层代码，

        如果是js，走stringByEvaluatingJavaScriptFromString()

        否则走：nativeLoadUrl()

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