利用BottomNavigationBar实现不同的fragment之间的转换

public class FragActivity_Me extends Fragment {

    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, 
@Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_3, container, false);
        return view;
    }
}

<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"
        android:orientation="vertical"
        tools:context=".TabBarActivity">

        <FrameLayout android:id="@+id/fragment_content"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_weight="1">
        </FrameLayout>

        <com.ashokvarma.bottomnavigation.BottomNavigationBar
            android:id="@+id/bottom_navigation_bar"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_gravity="bottom" />

    </LinearLayout>

public class FragActivity_Look extends Fragment {

    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, 
@Nullable Bundle savedInstanceState) {
        View view = inflater.inflate(R.layout.fragment_1, container, false);
        return view;
    }
}

    private BottomNavigationBar bottomNavigationBar;
    private FrameLayout frameLayout;
    private FragmentTransaction transaction;
    private FragActivity_Look fragActivity_look;
    private FragActivity_Map fragActivity_map;
    private FragActivity_Me fragActivity_me;
    private Fragment mFragment;

protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        frameLayout = (FrameLayout) findViewById(R.id.fragment_content);
        bottomNavigationBar = (BottomNavigationBar) findViewById(R.id.bottom_navigation_bar);
        bottomNavigationBar.setActiveColor(R.color.colorAccent)//设置Item选中颜色方法
                .setInActiveColor(R.color.colorPrimary)//设置Item未选中颜色方法
                .setBarBackgroundColor("#FFFFFF");//背景颜色
        bottomNavigationBar.setMode(BottomNavigationBar.MODE_FIXED);
        bottomNavigationBar.setBackgroundStyle(BottomNavigationBar.BACKGROUND_STYLE_STATIC);
        bottomNavigationBar.addItem(new BottomNavigationItem(R.mipmap.bt_look, "Look").
                setActiveColorResource(R.color.teal)) .addItem(new BottomNavigationItem(R.mipmap.bt_map, "Map").
                setActiveColorResource(R.color.blue)) .addItem(new BottomNavigationItem(R.mipmap.bt_user, "Me").
                setActiveColorResource(R.color.grey)) .setFirstSelectedPosition(1) .initialise();
        bottomNavigationBar.setTabSelectedListener(this);
        //initFragment();

        fragActivity_look=new FragActivity_Look();
        fragActivity_map = new FragActivity_Map();
        fragActivity_me = new FragActivity_Me();
        transaction = getSupportFragmentManager().beginTransaction();
        transaction.add(R.id.fragment_content, fragActivity_map).commit();
        mFragment = fragActivity_map;
    }

private void switchFragment(Fragment fragment) {
        //判断当前显示的Fragment是不是切换的Fragment
        if(mFragment != fragment) {
            //判断切换的Fragment是否已经添加过
            if (!fragment.isAdded()) {
                //如果没有，则先把当前的Fragment隐藏，把切换的Fragment添加上
                getSupportFragmentManager().beginTransaction().hide(mFragment)
                        .add(R.id.fragment_content,fragment).commit();
            } else {
                //如果已经添加过，则先把当前的Fragment隐藏，把切换的Fragment显示出来
                getSupportFragmentManager().beginTransaction().hide(mFragment).show(fragment).commit();
            }
            mFragment = fragment;
        }
    }

@Override
    public void onTabSelected(int position) {
        switch (position){
            case 0:
                switchFragment(fragActivity_look);
                break;
            case 1:
                switchFragment(fragActivity_map);
                break;
            case 2:
                switchFragment(fragActivity_me);
                break;
        }
    }

    @Override
    public void onTabUnselected(int position) {

    }

    @Override
    public void onTabReselected(int position) {

    }