Question

我正在尝试遵循Udacity的教程来使用Firebase构建聊天应用程序。尽管我遵循了所有说明，但是在按一下按钮时仍无法将数据写入Firebase实时数据库。

App在模拟器上完美运行。但是，每当我按下发送按钮时，数据库中都不会显示任何数据。检查该应用程序的屏幕截图。

添加了google services json文件。
在 Build.gradle（app）文件中添加了需要并应用Google Services插件的所有依赖项。
在 Build.grade（项目）文件中添加了Google服务类路径。
将Firebase安全规则更改为测试模式。

我在做什么错？请帮忙。

MainActivity.java文件如下所示：

package com.google.firebase.udacity.friendlychat;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.Editable;
import android.text.InputFilter;
import android.text.TextWatcher;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.ListView;
import android.widget.ProgressBar;

import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.DatabaseReference;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";

    public static final String ANONYMOUS = "anonymous";
    public static final int DEFAULT_MSG_LENGTH_LIMIT = 1000;

    private ListView mMessageListView;
    private MessageAdapter mMessageAdapter;
    private ProgressBar mProgressBar;
    private ImageButton mPhotoPickerButton;
    private EditText mMessageEditText;
    private Button mSendButton;

    private String mUsername;

    private FirebaseDatabase mFirebaseDatabase;
    private DatabaseReference mMessagesDatabaseReference;

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

        mUsername = ANONYMOUS;

        mFirebaseDatabase = FirebaseDatabase.getInstance();
        mMessagesDatabaseReference = mFirebaseDatabase.getReference().child("messages");

        // Initialize references to views
        mProgressBar = (ProgressBar) findViewById(R.id.progressBar);
        mMessageListView = (ListView) findViewById(R.id.messageListView);
        mPhotoPickerButton = (ImageButton) findViewById(R.id.photoPickerButton);
        mMessageEditText = (EditText) findViewById(R.id.messageEditText);
        mSendButton = (Button) findViewById(R.id.sendButton);

        // Initialize message ListView and its adapter
        List<FriendlyMessage> friendlyMessages = new ArrayList<>();
        mMessageAdapter = new MessageAdapter(this, R.layout.item_message, friendlyMessages);
        mMessageListView.setAdapter(mMessageAdapter);

        // Initialize progress bar
        mProgressBar.setVisibility(ProgressBar.INVISIBLE);

        // ImagePickerButton shows an image picker to upload a image for a message
        mPhotoPickerButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                // TODO: Fire an intent to show an image picker
            }
        });

        // Enable Send button when there's text to send
        mMessageEditText.addTextChangedListener(new TextWatcher() {
            @Override
            public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) {
            }

            @Override
            public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) {
                if (charSequence.toString().trim().length() > 0) {
                    mSendButton.setEnabled(true);
                } else {
                    mSendButton.setEnabled(false);
                }
            }

            @Override
            public void afterTextChanged(Editable editable) {
            }
        });
        mMessageEditText.setFilters(new InputFilter[]{new InputFilter.LengthFilter(DEFAULT_MSG_LENGTH_LIMIT)});

        // Send button sends a message and clears the EditText
        mSendButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                FriendlyMessage friendlyMessage = new FriendlyMessage(mMessageEditText.getText().toString(), mUsername, null);
                // Clear input box
                mMessageEditText.setText("");
            }
        });
    }

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

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        return super.onOptionsItemSelected(item);
    }
}

Answer 1

什么都没有进入数据库，因为您根本没有在数据库中写东西。您正在创建FriendlyMessage类的对象，但未对其进行任何操作。要解决此问题，请使用以下代码行将该对象写入Firebase数据库：

mMessagesDatabaseReference.push().setValue(friendlyMessage);

您应该在声明friendlyMessage对象之后立即放置这一行代码。

Answer 2

    // Send button sends a message and clears the EditText
    mSendButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            FriendlyMessage friendlyMessage = new FriendlyMessage(mMessageEditText.getText().toString(), mUsername, null);
            // here you have to write code for save to firebase DB
            mMessagesDatabaseReference.push().setValue(friendlyMessage);
            // Clear input box
            mMessageEditText.setText("");
        }
    });

之后，您必须从Firebase读取数据并将其添加到您的列表。

Android App无法将数据写入Firebase数据库

2 个答案: