为什么片段不会在导航抽屉中显示布局

Question

i created a navigation drawer which has a draft and sent ,i set the SentFragment and DraftFragment in my MainActivity like the code below , but it doesn't intent or show the layout? i dont have any error. what happened?

DraftFragment

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;

    }
}

MainActivity

   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();

Answer 1

Use this code in your MainActivity:-

  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;
}