仿QQ底部切换(Fragment + Radio)

<RelativeLayout 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" >   //activity_main.xml

    <FrameLayout    
        android:id="@+id/frame_container"    //主内容的区域
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@+id/div_view" >
    </FrameLayout>

    <View
        android:id="@+id/div_view"
        android:layout_width="fill_parent"
        android:layout_height="1.0px"
        android:layout_above="@+id/main_radiogroup"    //横线 在radiogroup的上面
        android:layout_marginBottom="2dip"
        android:background="#ffc9cacb" />

    <RadioGroup
        android:id="@+id/main_radiogroup"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true" //在父布局 的下面
        android:orientation="horizontal" >

        <RadioButton
            android:id="@+id/tab_rbo_question"
            style="@style/tab_textview"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"     //占 一 
             android:background="@null"
            android:button="@null"
            android:checked="true"     // 默认选中
             android:drawableTop="@drawable/selector_tab_question"    //"问他" 图片的选择器
             android:text="问他"
            android:textColor="@color/tv_checked_bg" />

        <RadioButton
            android:id="@+id/tab_rbo_message"
            style="@style/tab_textview"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@null"
            android:button="@null"
            android:drawableTop="@drawable/selector_tab_message"   // "消息" 图片选择器
             android:gravity="center_horizontal"     //居中
             android:text="消息" />

        <RadioButton
            android:id="@+id/tab_rbo_answer"
            style="@style/tab_textview"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@null"
            android:button="@null"
            android:drawableTop="@drawable/selector_tab_answer"  //"我要回答"  图片选择器器
              android:gravity="center_horizontal"
            android:text="我要回答" />

        <RadioButton
            android:id="@+id/tab_rbo_discover"
            style="@style/tab_textview"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@null"
            android:button="@null"
            android:drawableTop="@drawable/selector_tab_discover"    //"发现" 图片选择器
              android:gravity="center_horizontal"
            android:text="发现" />

        <RadioButton
            android:id="@+id/tab_rbo_user"
            style="@style/tab_textview"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:background="@null"
            android:button="@null"
            android:drawableTop="@drawable/selector_tab_user"   //"我" 图片选择器
              android:gravity="center_horizontal"
            android:text="我" />
    </RadioGroup>

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?> //selector_tab_question
<selector xmlns:android="http://schemas.android.com/apk/res/android"
    <item android:drawable="@drawable/tab_question_select" android:state_checked="true"></item>
    <item android:drawable="@drawable/tab_question_select" android:state_pressed="true"></item>
    <item android:drawable="@drawable/tab_question_nor"></item>
</selector>

    <style name="tab_textview">
        <item name="android:textSize">11sp</item>
        <item name="android:gravity">center_horizontal</item>
        <item name="android:drawablePadding">2dip</item>
    </style>

public class MainActivity extends FragmentActivity {
    /** 底部导航 */
    private RadioGroup main_radiogroup;
    private Fragment mCurrent; // 当前的mCurrent
    private TabFragment faxian; // 发现
    private TabFragment huida; // 回答
    private TabFragment denglu; // 登陆
    private TabFragment xiaoxi; // 消息
    private TabFragment wenta; // 问他

    // private FragmentManager fm;
    // private FragmentTransaction ft;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        main_radiogroup = (RadioGroup) this.findViewById(R.id.main_radiogroup);
        // fm = getSupportFragmentManager();
        // main_radiogroup 被选中 ,时候的监听器
        main_radiogroup
                .setOnCheckedChangeListener(new OnCheckedChangeListener() {

                    @SuppressLint("ResourceAsColor")
                    @Override
                    public void onCheckedChanged(RadioGroup group, int checkedId) {
                        /** 改变文字的颜色 */
                        int length = group.getChildCount();
                        for (int i = 0; i < length; i++) {
                            RadioButton radioButton = (RadioButton) group
                                    .getChildAt(i);
                            if (radioButton.getId() != checkedId) {
                                // 没有选中的 时候的文字颜色
                                radioButton.setTextColor(getResources()
                                        .getColor(R.color.tv_checked_nor));
                            } else { // 选中的时候的文字颜色
                                radioButton.setTextColor(getResources()
                                        .getColor(R.color.tv_checked_bg));
                            }
                        }
                        switch (checkedId) {
                        case R.id.tab_rbo_answer:
                            changeAnswer(); //切换回答
                            break;
                        case R.id.tab_rbo_discover:
                            changeDiscover(); //切换问他
                            break;
                        case R.id.tab_rbo_message:
                            changeMessage(); //消息
                            break;
                        case R.id.tab_rbo_question:
                            changeQuesion();
                            break;
                        case R.id.tab_rbo_user:  //用户
                            changeUser();
                            break;
                        }
                    }
                });
　　      mCurrent = new TabFragment(); //起始时候 给个值 ,不然会 报异常

        /** 默认选择第一个 */
        changeQuesion();
       }

    /**
     * 切换问他
     */
    private void changeQuesion() {
        if (wenta == null) {
            wenta = new TabFragment();
            Bundle bundle = new Bundle();
            bundle.putString("name", "问他");
            wenta.setArguments(bundle);
        }
        switchContent(wenta);
        // ft.replace(R.id.frame_container, tab1);
        // ft.commit();

    }

    /**
     * 切换消息
     */
    private void changeMessage() {
        if (xiaoxi == null) {
            xiaoxi = new TabFragment();
            Bundle bundle = new Bundle();
            bundle.putString("name", "消息");
            xiaoxi.setArguments(bundle);
        }
        switchContent(xiaoxi);
        // ft.replace(R.id.frame_container, tab1);
        // ft.commit();
    }

    /***
     * 切换登录
     */
    private void changeUser() {
        if (denglu == null) {
            denglu = new TabFragment();
            Bundle bundle = new Bundle();
            bundle.putString("name", "用户");
            denglu.setArguments(bundle);
        }
        switchContent(denglu);
        // ft.replace(R.id.frame_container, tab1);
        // ft.commit();
    }

    /***
     * 切换回答
     */
    private void changeAnswer() {
        if (huida == null) {
            huida = new TabFragment();
            Bundle bundle = new Bundle();
            bundle.putString("name", "回答");
            huida.setArguments(bundle);
        }
        switchContent(huida);
        // ft.replace(R.id.frame_container, tab1);
        // ft.commit();
    }

    /***
     * 切换发现
     */
    private void changeDiscover() {
        if (faxian == null) {
            faxian = new TabFragment();
            Bundle bundle = new Bundle();
            bundle.putString("name", "发现");
            faxian.setArguments(bundle);
        }
        switchContent(faxian);
        // ft.replace(R.id.frame_container, tab1);
        // ft.commit();
    }

    /** 修改显示的内容 不会重新加载 **/
    public void switchContent(Fragment to) {
        if (mCurrent != to) {
            FragmentTransaction transaction = getSupportFragmentManager()
                    .beginTransaction();
            if (!to.isAdded()) { // 先判断是否被add过
                transaction.hide(mCurrent).add(R.id.frame_container, to)
                        .commit(); // 隐藏当前的fragment，add下一个到Activity中
            } else {
                transaction.hide(mCurrent).show(to).commit(); // 隐藏当前的fragment，显示下一个
            }
            mCurrent = to;
        }
        // showContent();
    }
}

public class TabFragment extends Fragment {
    private String tab_name;
    @Override
    public void onAttach(Activity activity) {
        super.onAttach(activity);
        //得到 activity 传来的 值
        tab_name=getArguments().getString("name");
        
    }
    
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View view=inflater.inflate(R.layout.fragment_tab, container, false);
        TextView tv=(TextView) view.findViewById(R.id.textview1);
        tv.setText(tab_name);
        return view;
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >  //fragment_tab
    
    <TextView
        android:id="@+id/textview1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="100sp"
        android:layout_centerInParent="true"   // 居 父中间
        />

</RelativeLayout>