Question

我使用this课程制作了聊天应用。我测试了它：

然后我关闭了应用程序，稍后打开它。令人惊讶的是，所有消息都消失了：

只有当我退出并再次登录时，它们才会显示回来。如何解决这个bug？

我的代码：

MainActivity.java：

import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.design.widget.FloatingActionButton;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.EditText;
import android.widget.ListView;
import android.widget.Toast;

import com.firebase.ui.auth.AuthUI;
import com.firebase.ui.database.FirebaseListAdapter;
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.FirebaseDatabase;

public class MainActivity extends AppCompatActivity {
    private static final int SIGN_IN_REQUEST_CODE = 111;
    private FirebaseListAdapter<ChatMessage> adapter;
    private ListView listView;
    private String loggedInUserName = "";

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

        //find views by Ids
        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
        final EditText input = (EditText) findViewById(R.id.input);
        listView = (ListView) findViewById(R.id.list);

        if (FirebaseAuth.getInstance().getCurrentUser() == null) {
            // Start sign in/sign up activity
            startActivityForResult(AuthUI.getInstance()
                    .createSignInIntentBuilder()
                    .build(), SIGN_IN_REQUEST_CODE);
        } else {
            // User is already signed in, show list of messages
            showAllOldMessages();
        }

        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                if (input.getText().toString().trim().equals("")) {
                    Toast.makeText(MainActivity.this, "Please enter some texts!", Toast.LENGTH_SHORT).show();
                } else {
                    FirebaseDatabase.getInstance()
                            .getReference()
                            .push()
                            .setValue(new ChatMessage(input.getText().toString(),
                                    FirebaseAuth.getInstance().getCurrentUser().getDisplayName(),
                                    FirebaseAuth.getInstance().getCurrentUser().getUid())
                            );
                    input.setText("");
                }
            }
        });
    }

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

    @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) {
                            Toast.makeText(MainActivity.this, "You have logged out!", Toast.LENGTH_SHORT).show();
                            finish();
                        }
                    });
        }
        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) {
                Toast.makeText(this, "Signed in successful!", Toast.LENGTH_LONG).show();
                showAllOldMessages();
            } else {
                Toast.makeText(this, "Sign in failed, please try again later", Toast.LENGTH_LONG).show();

                // Close the app
                finish();
            }
        }
    }

    private void showAllOldMessages() {
        loggedInUserName = FirebaseAuth.getInstance().getCurrentUser().getUid();
        Log.d("Main", "user id: " + loggedInUserName);

        adapter = new MessageAdapter(this, ChatMessage.class, R.layout.item_in_message,
                FirebaseDatabase.getInstance().getReference());
        listView.setAdapter(adapter);
    }

    public String getLoggedInUserName() {
        return loggedInUserName;
    }
}

ChatMessage.java：

public class ChatMessage {
    private String messageText;
    private String messageUser;
    private String messageUserId;

    public ChatMessage(String messageText, String messageUser, String messageUserId) {
        this.messageText = messageText;
        this.messageUser = messageUser;
        this.messageUserId = messageUserId;
    }

    public ChatMessage(){

    }

    public String getMessageUserId() {
        return messageUserId;
    }

    public void setMessageUserId(String messageUserId) {
        this.messageUserId = messageUserId;
    }

    public String getMessageText() {
        return messageText;
    }

    public void setMessageText(String messageText) {
        this.messageText = messageText;
    }

    public String getMessageUser() {
        return messageUser;
    }

    public void setMessageUser(String messageUser) {
        this.messageUser = messageUser;
    }
}

ChatAdapter.java：

import android.text.format.DateFormat;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import com.firebase.ui.database.FirebaseListAdapter;
import com.google.firebase.database.DatabaseReference;

public class MessageAdapter extends FirebaseListAdapter<ChatMessage> {

    private MainActivity activity;

    public MessageAdapter(MainActivity activity, Class<ChatMessage> modelClass, int modelLayout, DatabaseReference ref) {
        super(activity, modelClass, modelLayout, ref);
        this.activity = activity;
    }

    @Override
    protected void populateView(View v, ChatMessage model, int position) {
        TextView messageText = (TextView) v.findViewById(R.id.message_text);
        TextView messageUser = (TextView) v.findViewById(R.id.message_user);

        messageText.setText(model.getMessageText());
        messageUser.setText(model.getMessageUser());
 }

    @Override
    public View getView(int position, View view, ViewGroup viewGroup) {
        ChatMessage chatMessage = getItem(position);
        if (chatMessage.getMessageUserId().equals(activity.getLoggedInUserName()))
            view = activity.getLayoutInflater().inflate(R.layout.item_out_message, viewGroup, false);
        else
            view = activity.getLayoutInflater().inflate(R.layout.item_in_message, viewGroup, false);

        //generating view
        populateView(view, chatMessage, position);

        return view;
    }

    @Override
    public int getViewTypeCount() {
        // return the total number of view types. this value should never change
        // at runtime
        return 2;
    }

    @Override
    public int getItemViewType(int position) {
        // return a value between 0 and (getViewTypeCount - 1)
        return position % 2;
    }
}

P.S我试图将下面的代码粘贴到MainActivity的onResume方法中，但没有任何好处发生。

    if (FirebaseAuth.getInstance().getCurrentUser() == null) {
        // Start sign in/sign up activity
        startActivityForResult(AuthUI.getInstance()
                .createSignInIntentBuilder()
                .build(), SIGN_IN_REQUEST_CODE);
    } else {
        // User is already signed in, show list of messages
        showAllOldMessages();
    }

P.P.S当我尝试在聊天中发送新消息时，当有错误时，我会看到它们。但是当我退出并再次登录时，这些消息就不存在了。

Answer 1

关闭并重新打开应用程序时检查日志，或者如果您想要使用firebase创建聊天应用程序的教程，请查看日志。

第1部分https://www.youtube.com/watch?v=wVCz1a3ogqk

第2部分https://www.youtube.com/watch?v=uX6_w6yhj4E

退出并重新打开应用程序时不显示聊天消息

1 个答案: