Android的Webview中，javascript怎么调用java方法

2012-06-22

Android的Webview中，javascript如何调用java方法PS：另外推荐下面这篇文章《用注解和pojo支撑起来的轻量级RE

Android的Webview中，javascript如何调用java方法

PS：另外推荐下面这篇文章《用注解和pojo支撑起来的轻量级REST框架--T2 》

http://blog.csdn.net/nanjingjiangbiao/article/details/7680702

今天调查一个线上Bug，发现是WebView中的一小段javascript，会直接调用到后台APK的一个Java事件，最后导致java中nullpointexception。

感兴趣的是，WebView中的javascript如何调用APK中的java方法。

一个例子：

通过JS取得Android的GPS数据

第一步，WebKit的准备

首先，给与WebKit的javascript的执行许可

public void onCreate(Bundle icicle) {  super.onCreate(icicle);  WebView wv = new WebView(this);  wv.getSettings().setJavaScriptEnabled(true);//JS利用OK  setContentView(wv);}

然后，塞入自己的javascript拦截器

JsObj jo = new JsObj(this);wv.addJavascriptInterface(jo, "roid");

第二步，定义自己的javascript拦截器

class JsObj {  private Context con;   public JsObj(Context con) {    this.con = con;  }   public String gps(String top, String end) {    LocationManager locman = (LocationManager)          con.getSystemService(Context.LOCATION_SERVICE);    Location loc = locman.getCurrentLocation("gps");    int lat = (int) (loc.getLatitude() * 1000000);    int lon = (int) (loc.getLongitude() * 1000000);    return top + "緯度:" + lat + ", 経度: " + lon + end;  }}

第三步，定义一个可运行的html

<html>  <head><title>JS calls Android Method</title></head>  <body>    <h1>JS on Android</h1>    <script type="text/javascript">      document.write(roid.gps("<i>", "</i>"));    </script>  </body></html>

在这个代码里面，可以用roid.gps的方法调用第二步定义的java函数

最后，全部的代码

package com.adamrocker.android.web; import android.app.Activity;import android.content.Context;import android.location.Location;import android.location.LocationManager;import android.os.Bundle;import android.webkit.WebView; public class WebkitTest extends Activity {  /** Called when the activity is first created. */  @Override   public void onCreate(Bundle icicle) {      super.onCreate(icicle);      WebView wv = new WebView(this);      wv.getSettings().setJavaScriptEnabled(true);      JsObj jo = new JsObj(this);      wv.addJavascriptInterface(jo, "roid");      setContentView(wv);      wv.loadUrl("http://www.adamrocker.com/android/js2android.html");  }    class JsObj {      private Context con;       public JsObj(Context con) {         this.con = con;      }       public String gps(String top, String end) {         LocationManager locman = (LocationManager) con              .getSystemService(Context.LOCATION_SERVICE);         Location loc = locman.getCurrentLocation("gps");         int lat = (int) (loc.getLatitude() * 1000000);         int lon = (int) (loc.getLongitude() * 1000000);         return top + "緯度:" + lat + ", 経度: " + lon + end;      }  }}

未完

我还想知道为什么，在webview里面定义一个JSObject，就可以连接javascript和后台函数

他们之间是如何通信的？

我稍微调查了一下WebView的底层代码，webview初期化的时候

/* Initialize private data within the WebCore thread.  */ private void  [More ...] initialize() {     /* Initialize our private BrowserFrame class to handle all      * frame-related functions. We need to create a new view which   * in turn creates a C level FrameView and attaches it to the frame.      */     mBrowserFrame = new BrowserFrame(mContext, this, mCallbackProxy,             mSettings, mJavascriptInterfaces);     mJavascriptInterfaces = null;     // Sync the native settings and also create the WebCore thread handler.     mSettings.syncSettingsAndCreateHandler(mBrowserFrame);     // Create the handler and transfer messages for the IconDatabase     WebIconDatabase.getInstance().createHandler();     // Create the handler for WebStorage     WebStorage.getInstance().createHandler();     // Create the handler for GeolocationPermissions.     GeolocationPermissions.getInstance().createHandler();     // The transferMessages call will transfer all pending messages to the     // WebCore thread handler.     mEventHub.transferMessages();     // Send a message back to WebView to tell it that we have set up the     // WebCore thread.     if (mWebView != null) {         Message.obtain(mWebView.mPrivateHandler,                 WebView.WEBCORE_INITIALIZED_MSG_ID,                 mNativeClass, 0).sendToTarget();     }     }

生成了显示用对象

Transfer all messages to the newly created webcore thread handler.  private void  [More ...] transferMessages() {      mTid = Process.myTid();      mSavedPriority = Process.getThreadPriority(mTid);      mHandler = new Handler() {          @Override          public void  [More ...] handleMessage(Message msg) {              if (DebugFlags.WEB_VIEW_CORE) {                  Log.v(LOGTAG, (msg.what < REQUEST_LABEL                          || msg.what                          > VALID_NODE_BOUNDS ? Integer.toString(msg.what)                          : HandlerDebugString[msg.what                                  - REQUEST_LABEL])                          + " arg1=" + msg.arg1 + " arg2=" + msg.arg2                          + " obj=" + msg.obj);              }              switch (msg.what) {                  case WEBKIT_DRAW:                      webkitDraw();
所以你要问我他们是怎么通信的
我只能说是线程间通信。
 
#以上#

 
1楼xiaofufu113小时前
谢谢分享。

热点排行

Web前端

Android的Webview中，javascript怎么调用java方法