导航抽屉活动，调用片段，空对象引用

Question

我哪里出错了？我试图在Communicate_fragment中设置editText并将其传递给Recieve_Fragment并将其显示在textView中。

这不会是一个问题如果我没有使用导航抽屉活动，因为我可以在MainAcitivty中绘制片段，这是我现在无法做到的，但我正在努力学习如何实现它以这种方式。

请指出我正确的方向，因为我是初学者，并试图学习工艺品。

AndroidManager说：

Attempt to invoke virtual method 'void fragmentdrawer.recieve_fragment.setText(java.lang.String)' on a null object reference

但我无法理解为什么。

主：

package com.example.name.fragmentdrawer;

import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.view.View;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;
import android.support.v4.app.FragmentManager;
import fragmentdrawer.about_me_fragment;
import fragmentdrawer.another_fragment;
import fragmentdrawer.communicate_fragment;
import fragmentdrawer.mainfragment;
import fragmentdrawer.recieve_fragment;



public class MainActivity extends AppCompatActivity
        implements NavigationView.OnNavigationItemSelectedListener, communicate_fragment.TopSectionListener{


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

        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);

        android.app.FragmentManager fm = getFragmentManager();
        fm.beginTransaction().replace(R.id.content_frame, new mainfragment()).commit();
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.

        android.app.FragmentManager fm = getFragmentManager();

        int id = item.getItemId();

        if (id == R.id.about_me) {
            fm.beginTransaction().replace(R.id.content_frame, new about_me_fragment()).commit();

        } else if (id == R.id.another_fragment) {
            fm.beginTransaction().replace(R.id.content_frame, new another_fragment()).commit();


        } else if (id == R.id.send) {
            fm.beginTransaction().replace(R.id.content_frame, new communicate_fragment()).commit();

        }
        else if (id == R.id.recieve) {
            fm.beginTransaction().replace(R.id.content_frame, new recieve_fragment()).commit();
        }

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

    public void createMeme(String text) {

        recieve_fragment texten = (recieve_fragment) getFragmentManager().findFragmentById(R.id.recieve);
        texten.setText(text);




    }
}

Communicate_fragmentclass：

 package fragmentdrawer;

    import android.app.Activity;
    import android.os.Bundle;
    import android.support.annotation.Nullable;
    import android.app.Fragment;
    import android.view.LayoutInflater;
    import android.view.View;
    import android.view.ViewGroup;
    import android.widget.Button;
    import android.widget.EditText;

    import com.example.name.fragmentdrawer.R;


    public class communicate_fragment extends Fragment{

        private static EditText topTextInput;
        private static Button button;


        TopSectionListener activityCommander;

        public interface TopSectionListener{
            public void createMeme(String text);

        }

        @Override
        public void onAttach(Activity activity) {
            super.onAttach(activity);
            try {
                activityCommander = (TopSectionListener) activity;
            }catch (ClassCastException e) {
                throw  new ClassCastException(activity.toString());
            }
        }




        @Nullable
        @Override
        public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_communicate, container, false);

            topTextInput = (EditText) rootView.findViewById(R.id.message);
            final Button button = (Button) rootView.findViewById(R.id.buttonSend);

            button.setOnClickListener(
                    new View.OnClickListener(){

                        public void onClick(View v){
                            buttonClicked(v);
                        }
                    }



            );



            return rootView;
        }

        public void buttonClicked(View view) {

            activityCommander.createMeme(topTextInput.getText().toString());



        }
    }

RECIEVE_CLASS_FRAMENT

package fragmentdrawer;

import android.os.Bundle;
import android.support.annotation.Nullable;
import android.app.Fragment;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.example.name.fragmentdrawer.R;

public class recieve_fragment extends Fragment{
    private static TextView textView;



    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_recieve, container, false);
        textView = (TextView) rootView.findViewById(R.id.displayMsg);
        return rootView;
    }

    public void setText(String text){
        textView.setText(text);
    }
}

Recieve_fragment.xml

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout 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">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:text="Medium Text"
        android:id="@+id/displayMsg"
        android:layout_gravity="center" />


</FrameLayout>