在开发商城上中时为了实现底部导航栏使用了fragmentTabHost方法，总结如下：

 1、Activity必须继承fragmentActivity方法。

 2.必须调用setup()方法 

 3.添加TabSpec  

具体代码如下: 

主要布局：

activity_main: 

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity"
    android:orientation="vertical">

    <FrameLayout
        android:id="@+id/realtabcontent"
        android:layout_width="fill_parent"
        android:layout_height="0dip"
        android:layout_weight="1"
        android:background="@color/colorAccent"
        />


    <android.support.v4.app.FragmentTabHost
        android:id="@android:id/tabhost"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        >

        <FrameLayout
            android:id="@android:id/tabcontent"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:layout_weight="0" />
    </android.support.v4.app.FragmentTabHost>
</LinearLayout>

主要代码逻辑: 

public class MainActivity extends AppCompatActivity {
    private FragmentTabHost mTabHost;
    private LayoutInflater mInflater;
    private List<Tab> mTabs = new ArrayList<>(5);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initTab();

    }

    private void initTab() {
        Tab tab_home = new Tab(HomeFragment.class,R.string.home,R.mipmap.icon_home);
        Tab tab_hot = new Tab(HotFragment.class,R.string.hot,R.mipmap.icon_hot);
        Tab tab_category = new Tab(CategoryFragment.class,R.string.catagory,R.mipmap.icon_discover);
        Tab tab_cart = new Tab(CartFragment.class,R.string.cart,R.mipmap.icon_cart);
        Tab tab_mine= new Tab(MineFragment.class,R.string.mine,R.mipmap.icon_user);

        mTabs.add(tab_home);
        mTabs.add(tab_hot);
        mTabs.add(tab_category);
        mTabs.add(tab_cart);
        mTabs.add(tab_mine);

        mInflater = LayoutInflater.from(this);
        mTabHost  = (FragmentTabHost) findViewById(android.R.id.tabhost);
        mTabHost.setup(this,getSupportFragmentManager(),R.id.realtabcontent);

        for(Tab tab : mTabs){
            TabHost.TabSpec tabSpec = mTabHost.newTabSpec(getString(tab.getTitle()));
            tabSpec.setIndicator( buildindictor(tab));
            mTabHost.addTab(tabSpec,tab.getFragment(),null);

        }

    }
    private View buildindictor(Tab tab){
        View view = mInflater.inflate(R.layout.tab_indication,null);
        ImageView img = (ImageView) findViewById(R.id.icon_tab);
        TextView txt = (TextView) findViewById(R.id.txt_indicator);

        img.setBackgroundResource(tab.getIcon());
        txt.setText(tab.getTitle());
        return view;

    }
} 

在新建CartFragment:\CategoryFragment;\.HomeFragment;\.HotFragment;\.MineFragmen类，都必须继承v4包下的Fragment
public class HotFragment extends Fragment {
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        return  inflater.inflate(R.layout.fragment_hot,container,false);
    }
}

FragmentTabHost的使用方法总结