Java 为什么fragment没有在我的导航抽屉中显示布局

我创建了一个导航抽屉，它有一个草稿并已发送，我在MainActivity中设置了SentFragment和DraftFragment，如下代码所示，但它没有意图或显示布局？我没有任何错误。发生了什么事

气流碎片

package com.test.mypc.androidtestme;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;


public class DraftFragment extends Fragment {

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

SentFragment

package com.test.mypc.androidtestme;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;


public class SentFragment extends Fragment {


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

    }
}

主要活动

   mFragmentManager = getSupportFragmentManager();
        mFragmentTransaction = mFragmentManager.beginTransaction();
        mFragmentTransaction.replace(R.id.containerView, new SentFragment()).commit();


        mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(MenuItem menuItem) {
                mDrawerLayout.closeDrawers();

                if (menuItem.getItemId() == R.id.nav_item_sent) {

                    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                    fragmentTransaction.replace(R.id.containerView, new SentFragment()).commit();

                }
                if (menuItem.getItemId() == R.id.nav_item_draft) {
                    FragmentTransaction ft_drafts = mFragmentManager.beginTransaction();
                    ft_drafts.replace(R.id.containerView, new DraftFragment()).commit();
                }
                return false;
            }

        });

        android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
        ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, toolbar, R.string.app_name,
                R.string.app_name);
        mDrawerLayout.setDrawerListener(mDrawerToggle);
        mDrawerToggle.syncState();

---

在主要活动中使用此代码：-

  public boolean onNavigationItemSelected(MenuItem item) {
    // Handle navigation view item clicks here.
    fragment = null;
    int id = item.getItemId();
    String get_title = item.getTitle().toString();

    if (id == R.id.nav_item_sent) {

        fragment = new SentFragment();

    } else if (id == R.id.nav_item_draft) {
        fragment = new DraftFragment();

    }

    if (fragment != null) {
        FragmentTransaction ft = getSupportFragmentManager().beginTransaction();
        ft.replace(R.id.content_frame, fragment);
        ft.commit();
    }

    title_tv.setText(get_title);
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    drawer.closeDrawer(GravityCompat.START);
    return true;
}

---

@菲塔·洛德，如果你认为这很有用，那么选择答案，让其他人从中受益。。感谢您对@Laxmeena的评论，但即使没有错误，也不会发生任何事情。ahmm@FitaLord，只需创建一个新的示例Navigtion Drawer应用程序，并尝试根据您的需要修改该应用程序。根据我上面的代码，您认为使用fragment有错误吗？我认为我上面的代码与你的代码相似。我有点困惑。