为什么滑动标签的片段与导航抽屉片段重叠？

Question

我正在尝试使用导航抽屉和滑动标签创建应用，我希望我的滑动标签始终像工具栏一样可见。我的问题是滑动条和导航抽屉的片段是重叠的。 the image of my app
任何人都可以帮助我。这是我的代码的一些安宁：  MainActivity

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

//=============
viewPager = (ViewPager) findViewById(R.id.viewpager);
setupViewPager(viewPager);
//=============
tabLayout = (TabLayout) findViewById(R.id.tabs);
tabLayout.setupWithViewPager(viewPager);
//=============

mHandler = new Handler();

drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
navigationView = (NavigationView) findViewById(R.id.nav_view);
fab = (FloatingActionButton) findViewById(R.id.fab);


setUpNavigationView();


}

/***
 * Swipe Tabs
 */
private void setupViewPager(ViewPager viewPager) {
    ViewPagerAdapter adapter = new      ViewPagerAdapter(getSupportFragmentManager());
    adapter.addFragment(new HomeFragment(), "ONE");
    adapter.addFragment(new AgendaFragment(), "TWO");
    adapter.addFragment(new NotificationFragment(), "THREE");
    viewPager.setAdapter(adapter);
}

class ViewPagerAdapter extends FragmentPagerAdapter {
    private final List<Fragment> mFragmentList = new ArrayList<>();
    private final List<String> mFragmentTitleList = new ArrayList<>();

    public ViewPagerAdapter(FragmentManager manager) {
        super(manager);
    }

    @Override
    public Fragment getItem(int position) {
        return mFragmentList.get(position);
    }

    @Override
    public int getCount() {
        return mFragmentList.size();
    }

    public void addFragment(Fragment fragment, String title) {
        mFragmentList.add(fragment);
        mFragmentTitleList.add(title);
    }

    @Override
    public CharSequence getPageTitle(int position) {
        return mFragmentTitleList.get(position);
    }
}


/***
 * Returns respected fragment that user
 * selected from navigation menu
 */
private void loadHomeFragment() {
    // selecting appropriate nav menu item
    selectNavMenu();

    // if user select the current navigation menu again, don't do anything
    // just close the navigation drawer
    if (getSupportFragmentManager().findFragmentByTag(CURRENT_TAG) != null) {
        drawer.closeDrawers();

        // show or hide the fab button
        toggleFab();
        return;
    }


    Runnable mPendingRunnable = new Runnable() {
        @Override
        public void run() {
            // update the main content by replacing fragments
            Fragment fragment = getHomeFragment();
            if(fragment != null){
            FragmentTransaction fragmentTransaction = getSupportFragmentManager().beginTransaction();
            fragmentTransaction.setCustomAnimations(android.R.anim.fade_in,
                    android.R.anim.fade_out);
            fragmentTransaction.replace(R.id.frame, fragment, CURRENT_TAG);
            fragmentTransaction.commitAllowingStateLoss();}

        }
    };

    // If mPendingRunnable is not null, then add to the message queue
    if (mPendingRunnable != null) {
        mHandler.post(mPendingRunnable);
    }

    // show or hide the fab button
    toggleFab();

    //Closing drawer on item click
    drawer.closeDrawers();

    // refresh toolbar menu
    invalidateOptionsMenu();
}

private Fragment getHomeFragment() {
    switch (navItemIndex) {
        case 0:
            // item1
            ItemoneFragment itemoneFragment= new ItemoneFragment();
            return my_selectionFragment;
        case 1:
            // item2
            ItemtowFragment itemtowFragment = new ItemtowFragment();
            return my_activitiesFragment;
        case 2:
            // item3
            ItemthreeFragment itemthreeFragment = new ItemthreeFragment();
            return groupFragment;


        default:
            return null;
    }
}



private void selectNavMenu() {
    navigationView.getMenu().getItem(navItemIndex).setChecked(true);
}

private void setUpNavigationView() {
    //Setting Navigation View Item Selected Listener to handle the item click of the navigation menu
    navigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {

        // This method will trigger on item Click of navigation menu
        @Override
        public boolean onNavigationItemSelected(MenuItem menuItem) {

            //Check to see which item was being clicked and perform appropriate action
            switch (menuItem.getItemId()) {
                //Replacing the main content with ContentFragment Which is our Inbox View;
                case R.id.nav_my_activities:
                    navItemIndex = 0;
                    CURRENT_TAG = TAG_HOME;
                    break;
                case R.id.nav_my_selection:
                    navItemIndex = 1;
                    CURRENT_TAG = TAG_PHOTOS;
                    break;
                case R.id.nav_group:
                    navItemIndex = 2;
                    CURRENT_TAG = TAG_GROUPS;
                    break;


                default:
                    navItemIndex = 0;
            }

            //Checking if the item is in checked state or not, if not make it in checked state
            if (menuItem.isChecked()) {
                menuItem.setChecked(false);
            } else {
                menuItem.setChecked(true);
            }
            menuItem.setChecked(true);

            loadHomeFragment();

            return true;
        }
    });


    ActionBarDrawerToggle actionBarDrawerToggle = new ActionBarDrawerToggle(this, drawer, toolbar, R.string.openDrawer, R.string.closeDrawer) {

        @Override
        public void onDrawerClosed(View drawerView) {
            // Code here will be triggered once the drawer closes as we dont want anything to happen so we leave this blank
            super.onDrawerClosed(drawerView);
        }

        @Override
        public void onDrawerOpened(View drawerView) {
            // Code here will be triggered once the drawer open as we dont want anything to happen so we leave this blank
            super.onDrawerOpened(drawerView);
        }
    };

    //Setting the actionbarToggle to drawer layout
    drawer.setDrawerListener(actionBarDrawerToggle);

    //calling sync state is necessary or else your hamburger icon wont show up
    actionBarDrawerToggle.syncState();
}

activity_main.xml

<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/drawer_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:openDrawer="start">

    <include
        layout="@layout/app_bar_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/nav_header_main"
        app:menu="@menu/activity_main_drawer"
        />




</android.support.v4.widget.DrawerLayout>

app_bar_main.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.design.widget.CoordinatorLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fitsSystemWindows="true"
    tools:context="com.myApp.activities.MainActivity">

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:theme="@style/AppTheme.AppBarOverlay">

        <android.support.v7.widget.Toolbar
            android:id="@+id/toolbar"
            android:layout_width="match_parent"
            android:layout_height="?attr/actionBarSize"
            android:background="?attr/colorPrimary"
            app:popupTheme="@style/AppTheme.PopupOverlay" />

        <android.support.design.widget.TabLayout
            android:id="@+id/tabs"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:tabMode="fixed"
            app:tabGravity="fill"/>



    </android.support.design.widget.AppBarLayout>

    <android.support.v4.view.ViewPager
        android:id="@+id/viewpager"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior" />

    <FrameLayout
        android:id="@+id/frame"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"></FrameLayout>

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom|end"
        android:layout_margin="@dimen/fab_margin"
        app:backgroundTint="@color/colorPrimary"
        app:srcCompat="@android:drawable/ic_dialog_email" />

</android.support.design.widget.CoordinatorLayout>