安卓实现底部菜单

这是我写的实现安卓底部菜单，但没报错也没显示，不知哪里错了请大侠们看看
package com.jifenbang.app;import java.util.ArrayList;
import java.util.List;import android.app.Activity;
import android.app.TabActivity;
import android.content.Intent;
import android.content.res.Resources;
import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.RadioButton;
import android.widget.RadioGroup;
import android.widget.TabHost;
import android.widget.RadioGroup.OnCheckedChangeListener;public class mainPage extends TabActivity {
private TabHost tabHost;
private RadioGroup radioGroup;
private Resources rec;
private Intent intent;

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
   setContentView(R.layout.home_page);
   radioGroup = (RadioGroup)findViewById(R.id.main_radio);
   tabHost = getTabHost();
   rec = getResources();
   
   add(R.string.home, home.class, R.drawable.icon_1_n);
   add(R.string.home, exchange.class, R.drawable.icon_2_n);
   add(R.string.home, give.class, R.drawable.icon_3_n);
   add(R.string.home, search.class, R.drawable.icon_4_n);
   add(R.string.home, more.class, R.drawable.icon_5_n);
}
protected void onStart(){
super.onStart();

radioGroup.setOnCheckedChangeListener(new OnCheckedChangeListener() {
public void onCheckedChanged(RadioGroup group, int checkedId) {
switch (checkedId) {
case R.id.radio_button0:
tabHost.setCurrentTabByTag(rec.getString(R.string.home));
break;
case R.id.radio_button1:
tabHost.setCurrentTabByTag(rec.getString(R.string.exchange));
break;
case R.id.radio_button2:
tabHost.setCurrentTabByTag(rec.getString(R.string.give));
break;
case R.id.radio_button3:
tabHost.setCurrentTabByTag(rec.getString(R.string.search));
break;
case R.id.radio_button4:
tabHost.setCurrentTabByTag(rec.getString(R.string.more));
break;
default:
break;
}
}
});
}
protected void  add(int name,Class<?>c,int icon) {
TabHost.TabSpec tab = tabHost.newTabSpec(rec.getString(name));
tab.setIndicator(rec.getString(name), rec.getDrawable(icon));
intent = new Intent();
intent.setClass(this, c);
tab.setContent(intent);
tabHost.addTab(tab);
}
}
<?xml version="1.0" encoding="utf-8"?>
<TabHost xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@android:id/tabhost"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >    <LinearLayout
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:orientation="vertical" >        <FrameLayout
            android:id="@android:id/tabcontent"
            android:layout_width="fill_parent"
            android:layout_height="0.0dip"
            android:layout_weight="1.0" />        <TabWidget
            android:id="@android:id/tabs"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_weight="0.0"
            android:tabStripEnabled="false"
            android:visibility="gone" />        <RadioGroup
            android:id="@+id/main_radio"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom"
            android:gravity="center_vertical"
            android:orientation="horizontal" >            <RadioButton
                android:id="@+id/radio_button0"
                style="@style/main_tab_bottom"
                android:layout_marginTop="2.0dip"
                android:drawableTop="@drawable/icon_1_n"
                android:tag="radio_button0"
                android:text="@string/home" />            <RadioButton
                android:id="@+id/radio_button1"
                style="@style/main_tab_bottom"
                android:layout_marginTop="2.0dip"
                android:drawableTop="@drawable/icon_2_n"
                android:tag="radio_button1"
                android:text="@string/exchange" />            <RadioButton
                android:id="@+id/radio_button2"
                style="@style/main_tab_bottom"
                android:layout_marginTop="2.0dip"
                android:drawableTop="@drawable/icon_3_n"
                android:tag="radio_button2"
                android:text="@string/give" />            <RadioButton
                android:id="@+id/radio_button3"
                style="@style/main_tab_bottom"
                android:layout_marginTop="2.0dip"
                android:drawableTop="@drawable/icon_4_n"
                android:tag="radio_button3"
                android:text="@string/search" />            <RadioButton
                android:id="@+id/radio_button4"
                style="@style/main_tab_bottom"
                android:layout_marginTop="2.0dip"
                android:drawableTop="@drawable/icon_5_n"
                android:tag="radio_button4"
                android:text="@string/more" />
        </RadioGroup>
    </LinearLayout></TabHost>Android布局tag