如何给webview页面自定义404页面

//示例地图类
package com.can2do.doimobile.news;

import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.TextView;

import com.can2do.doimobile.R;
import com.can2do.doimobile.base.BaseUiWeb;
import com.can2do.doimobile.base.C;

public class UiNewsOne extends BaseUiWeb {

    private String tag = null;
    private WebView mWebViewMap;

    @Override
    public void onStart() {
        super.onStart();

        setContentView(R.layout.ui_news_one);

        Bundle params = this.getIntent().getExtras();
        tag = params.getString("tag");

        TextView titleText = (TextView) this
                .findViewById(R.id.main_top_title1);
        titleText.setText(tag);

        mWebViewMap = (WebView) findViewById(R.id.web_news_one);
        mWebViewMap.getSettings().setJavaScriptEnabled(true);
        mWebViewMap.setWebViewClient(new WebViewClient(){
        });
        mWebViewMap.setWebViewClient(new WebViewClient() {
             public void onReceivedError(WebView view, int errorCode, String description, String failingUrl)
             {
                 view.stopLoading();
                 view.clearView();
                 Message msg=handler.obtainMessage();//发送通知，加入线程
                 msg.what=1;//通知加载自定义404页面
                 handler.sendMessage(msg);//通知发送！
             }
             public boolean shouldOverrideUrlLoading(WebView view, String url)
             {
                 view.loadUrl(url);
                 return true;
             }
        });
        mWebViewMap.loadUrl(C.news.news1);

        this.setWebView(mWebViewMap);
        this.startWebView();
    }

     protected Handler handler = new Handler(){
         public void handleMessage(Message message){
             switch (message.what) {
             case 1:
                 mWebViewMap.loadUrl("file:///android_asset/www/404/404.html");
                 break;
             }
         }
     };

}