fragment中的WebView返回上一页

 public final class Text1Fm extends Fragment {  

     static WebView mWeb;
     private View mContentView;
     private static final String APP_CACAHE_DIRNAME = "/webcache";  

     private Handler handler = new Handler() {
         @Override
         public void handleMessage(Message message) {
             switch (message.what) {
                 case 1: {
                      mWeb.goBack();
                 }
                 break;
             }
         }
     };
     @Override
     public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {  

         mContentView = inflater.inflate(R.layout.baiduwebview, null);
         mWeb = (WebView) mContentView.findViewById(R.id.wv);  

         WebSettings settings = mWeb.getSettings();
         settings.setJavaScriptEnabled(true);
         mWeb.setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY);
         mWeb.getSettings().setSupportZoom(true);  //支持放大缩小
         mWeb.getSettings().setBuiltInZoomControls(true);
         mWeb.loadUrl("你的网址");
         settings.setUseWideViewPort(true);
         settings.setLoadWithOverviewMode(true);
         mWeb.getSettings().setSaveFormData(true);// 保存表单数据
         mWeb.setWebViewClient(new WebViewClient());
         String cacheDirPath = getActivity().getFilesDir().getAbsolutePath() + APP_CACAHE_DIRNAME; //缓存路径  

         mWeb.getSettings().setCacheMode(WebSettings.LOAD_CACHE_ELSE_NETWORK);  //缓存模式
         mWeb.getSettings().setAppCachePath(cacheDirPath); //设置缓存路径
         mWeb.getSettings().setAppCacheEnabled(true); //开启缓存功能  

         mWeb.setOnKeyListener(new View.OnKeyListener() {  

             public boolean onKey(View v, int keyCode, KeyEvent event) {
                 if ((keyCode == KeyEvent.KEYCODE_BACK) && mWeb.canGoBack()) { 
                      if(keyEvent.getAction()==KeyEvent.ACTION_DOWN){ //只处理一次
                     handler.sendEmptyMessage(1);  
                       }
                     return true;
                 }
                 return false;
             }  

         });
         return mContentView;
     }
 }