如何用片段布局替换线性布局的内容

Question

activity_main.xml中

大家好，这里我有线性和帧布局，我打算在开始时显示我的线性，然后我创建的工具栏包含将在片段中显示的项目列表，问题是我无法覆盖线性布局的内容在我选择片段

之后

<LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <include
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            layout="@layout/toolbar"/>
            <ImageView

            android:layout_width="90dp"
            android:layout_height="90dp"
            android:id="@+id/logo"
            android:src="@drawable/splash_img1"
            android:layout_gravity="center"/>
        <GridView
            android:id="@+id/gridview"
            android:numColumns="2"
            android:gravity="center"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@id/logo" />

    <FrameLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/main_container">
    </FrameLayout>
</LinearLayout>

MainActivity.java

来自android监视器的

错误表示行指针的空指针getsupportactionbar.settittle

        ft = getSupportFragmentManager().beginTransaction();
        ft.add(R.id.main_container, new HomeFragment());
        ft.commit();
        getSupportActionBar().setTitle("Home Fragment...");
        nv = (NavigationView) findViewById(R.id.navigation_view);
        nv.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener(){
            @Override
            public boolean onNavigationItemSelected(MenuItem item){
                switch(item.getItemId()){
                    case R.id.home_id:
                        ft = getSupportFragmentManager().beginTransaction();
                        ft.replace(R.id.main_container, new HomeFragment());
                        ft.commit();
                        getSupportActionBar().setTitle("Home Fragment");
                        item.setChecked(true);
                        dl.closeDrawers();
                        break;

                    case R.id.setting_id:
                        ft = getSupportFragmentManager().beginTransaction();
                        ft.replace(R.id.main_container, new Setting_Fragment());
                        ft.commit();
                        getSupportActionBar().setTitle("Setting Fragment");
                        item.setChecked(true);
                        dl.closeDrawers();
                        break;

                       ........// I dont display all since this rest is working fine