单击聊天应用程序中的“发送”按钮时，布局上没有消息

Question

我正在使用教程开发聊天应用程序。我已经连接了fire-base并且有ID.I安装了apk并且我正确登录。在文本框中写入文本后，单击“发送”按钮（在代码中由“fab”定义）。点击之后，上面没有显示任何内容。但它将消息存储在数据库中。我把它放在主要活动java代码中。问题是什么？

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.RelativeLayout;
import android.widget.TextView;
import android.text.format.DateFormat;

import com.firebase.ui.auth.AuthUI;
import com.firebase.ui.database.FirebaseListAdapter;
import com.firebase.ui.database.FirebaseListOptions;
import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.Query;
import com.google.firebase.database.ValueEventListener;


public class MainActivity extends AppCompatActivity {
    private static int SIGN_IN_REQUEST_CODE = 1;
    private FirebaseListAdapter<ChatMessage> adapter;
    RelativeLayout activity_main;
    FloatingActionButton fab;

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if (item.getItemId() == R.id.menu_sign_out) {
            AuthUI.getInstance().signOut(this).addOnCompleteListener(new OnCompleteListener<Void>() {
                @Override
                public void onComplete(@NonNull Task<Void> task) {
                    Snackbar.make(activity_main, "You have been signed out.", Snackbar.LENGTH_SHORT).show();
                     finish();
                }
            });

        }

        return true;
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main_menu, menu);
        return true;
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == SIGN_IN_REQUEST_CODE) {
            if (resultCode == RESULT_OK) {
                Snackbar.make(activity_main, "Successfully signed in.Welcome!", Snackbar.LENGTH_SHORT).show();
                displayChatMessage();

            } else {
                Snackbar.make(activity_main, "We couldn't sign you in.Please try again later", Snackbar.LENGTH_SHORT).show();
                finish();

            }

        }
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        activity_main = (RelativeLayout) findViewById(R.id.activity_main);
        fab = (FloatingActionButton) findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                EditText input = (EditText)findViewById(R.id.input);
                FirebaseDatabase.getInstance().getReference().push().setValue(new ChatMessage(input.getText().toString(),
                        FirebaseAuth.getInstance().getCurrentUser().getEmail()));
                input.setText("");

            }
        });
        //check if not sign-in then navigate signin page
        if (FirebaseAuth.getInstance().getCurrentUser() == null) {
            startActivityForResult(AuthUI.getInstance().createSignInIntentBuilder().build(), SIGN_IN_REQUEST_CODE);

        } else {
            Snackbar.make(activity_main, "Welcome" + FirebaseAuth.getInstance().getCurrentUser().getEmail(), Snackbar.LENGTH_SHORT).show();
            //Load content
            displayChatMessage();

        }

    }

    private void displayChatMessage() {


            ListView listOfMessage = (ListView) findViewById(R.id.list_of_message);
            Query query = FirebaseDatabase.getInstance().getReference().child("chats");
            FirebaseListOptions<ChatMessage> options =
                    new FirebaseListOptions.Builder<ChatMessage>()
                            .setQuery(query, ChatMessage.class)
                            .setLayout(R.layout.list_item)
                            .build();
            adapter = new FirebaseListAdapter<ChatMessage>(options){
                @Override
                protected void populateView(View v, ChatMessage model, int position) {


                    //get reference to the views of simple_list_item_1st_item_1.xml
                    TextView messageText, messageUser, messageTime;
                    messageText = (TextView) v.findViewById(R.id.message_text);
                    messageUser = (TextView) v.findViewById(R.id.message_user);
                    messageTime = (TextView) v.findViewById(R.id.message_time);

                    messageText.setText(model.getMessageText());
                    messageUser.setText(model.getMessageUser());
                    messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss))", model.getMessageTime()));


                }

            };

            listOfMessage.setAdapter(adapter);


    }

}