Android Activity 和 HTML 数据通信

package com.lmn.webview.html;      import android.app.Activity;   import android.app.AlertDialog;   import android.app.AlertDialog.Builder;   import android.content.DialogInterface;   import android.os.Bundle;   import android.os.Handler;   import android.os.Message;   import android.view.Window;   import android.webkit.JsResult;   import android.webkit.WebChromeClient;   import android.webkit.WebSettings;   import android.webkit.WebStorage;   import android.webkit.WebView;   import android.widget.Toast;      public class MainActivity extends Activity {       private WebView mWebView;          /** Called when the activity is first created. */       @Override       public void onCreate(Bundle savedInstanceState) {           super.onCreate(savedInstanceState);           setContentView(R.layout.main);           mWebView = (WebView) findViewById(R.id.webview);              WebSettings webSettings = mWebView.getSettings();           webSettings.setSavePassword(false);           webSettings.setSaveFormData(false);           webSettings.setJavaScriptEnabled(true);           webSettings.setSupportZoom(true);              // Horizontal水平方向，Vertical竖直方向            mWebView.setHorizontalScrollBarEnabled(false);           mWebView.setVerticalScrollBarEnabled(false);              mWebView.setWebChromeClient(new WebChromeClient() {               // 处理javascript中的alert                public boolean onJsAlert(WebView view, String url, String message,                       final JsResult result) {                   // 构建一个Builder来显示网页中的对话框                    Builder builder = new Builder(MainActivity.this);                   builder.setTitle("Alert");                   builder.setMessage(message);                   builder.setPositiveButton(android.R.string.ok,                           new AlertDialog.OnClickListener() {                               public void onClick(DialogInterface dialog,                                       int which) {                                   // 点击确定按钮之后,继续执行网页中的操作                                    result.confirm();                               }                           });                   builder.setCancelable(false);                   builder.create();                   builder.show();                   return true;               };                  // 处理javascript中的confirm                public boolean onJsConfirm(WebView view, String url,                       String message, final JsResult result) {                   Builder builder = new Builder(MainActivity.this);                   builder.setTitle("confirm");                   builder.setMessage(message);                   builder.setPositiveButton(android.R.string.ok,                           new AlertDialog.OnClickListener() {                               public void onClick(DialogInterface dialog,                                       int which) {                                   result.confirm();                               }                           });                   builder.setNegativeButton(android.R.string.cancel,                           new DialogInterface.OnClickListener() {                               public void onClick(DialogInterface dialog,                                       int which) {                                   result.cancel();                               }                           });                   builder.setCancelable(false);                   builder.create();                   builder.show();                   return true;               };                  // 设置网页加载的进度条                public void onProgressChanged(WebView view, int newProgress) {                   MainActivity.this.getWindow().setFeatureInt(                           Window.FEATURE_PROGRESS, newProgress * 100);                   super.onProgressChanged(view, newProgress);               }                  // 设置应用程序的标题title                public void onReceivedTitle(WebView view, String title) {                   MainActivity.this.setTitle(title);                   super.onReceivedTitle(view, title);               }                  public void onReachedMaxAppCacheSize(long spaceNeeded,                       long totalUsedQuota, WebStorage.QuotaUpdater quotaUpdater) {                   quotaUpdater.updateQuota(spaceNeeded * 2);               }           });                         mWebView.addJavascriptInterface(new JavaScriptInterface(), "demo");           mWebView.loadUrl("file:///android_asset/demo.html");       }          final class JavaScriptInterface {           JavaScriptInterface() {           }              public int mydata() {               return 10;           }              public void DataFromHtml(String resHtml) {               Message m = new Message();               m.obj = resHtml;               h.sendMessage(m);           }       }          Handler h = new Handler() {           public void handleMessage(Message msg) {               Toast.makeText(MainActivity.this, msg.obj + "", Toast.LENGTH_LONG)                       .show();           }       };   }