Question

我目前正在通过创建一种小型聊天应用来试验Firebase。我能够将数据发送到数据库引用，但是我希望通过以下代码显示它。但事实并非如此，我想知道我在列表中使用适配器的方式是否有问题。

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

        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. Therefore, display
            // a welcome Toast
            Toast.makeText(this,
                    "Welcome " + FirebaseAuth.getInstance()
                            .getCurrentUser()
                            .getDisplayName(),
                    Toast.LENGTH_LONG)
                    .show();

            displayChatMessages();
        }

        FloatingActionButton fab = (FloatingActionButton)findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                EditText input = (EditText)findViewById(R.id.input);

                // Read the input field and push a new instance
                // of ChatMessage to the Firebase database
                FirebaseDatabase.getInstance()
                        .getReference()
                        .push()
                        .setValue(new ChatMessage(input.getText().toString(),
                                FirebaseAuth.getInstance()
                                        .getCurrentUser()
                                        .getDisplayName())
                        );

                // Clear the input
                input.setText("");
            }
        });

    }

    private void displayChatMessages() {
        ListView listOfMessages = (ListView)findViewById(R.id.list_of_messages);

        Query query = FirebaseDatabase.getInstance().getReference();

        FirebaseListOptions<ChatMessage> options = new FirebaseListOptions.Builder<ChatMessage>()
                .setQuery(query, ChatMessage.class)
                .setLayout(R.layout.message)
                .build();

        adapter = new FirebaseListAdapter<ChatMessage>( options ) {
            @Override
            protected void populateView(View v, ChatMessage model, int position) {
                // Get references to the views of message.xml
                TextView messageText = (TextView)v.findViewById(R.id.message_text);
                TextView messageUser = (TextView)v.findViewById(R.id.message_user);
                TextView messageTime = (TextView)v.findViewById(R.id.message_time);

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

        listOfMessages.setAdapter(adapter);

    }

 @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,
                        "Successfully signed in. Welcome!",
                        Toast.LENGTH_LONG)
                        .show();
                displayChatMessages();
            } else {
                Toast.makeText(this,
                        "We couldn't sign you in. Please try again later.",
                        Toast.LENGTH_LONG)
                        .show();

                // Close the app
                finish();
            }
        }

    }

}

以下是主要活动的用户界面

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/activity_main"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="citroentrex.citron.MainActivity">

    <android.support.design.widget.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentEnd="true"
        android:layout_alignParentRight="true"
        android:clickable="true"
        android:tint="@android:color/white"
        app:fabSize="mini"
        />

    <android.support.design.widget.TextInputLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@id/fab"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true">

        <EditText
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:hint="Input"
            android:id="@+id/input"
            />
    </android.support.design.widget.TextInputLayout>

    <ListView
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:layout_alignParentTop="true"
      android:layout_alignParentLeft="true"
      android:dividerHeight="16dp"
      android:divider="@android:color/transparent"
      android:layout_above="@id/fab"
      android:id="@+id/list_of_messages"
      android:layout_marginBottom="16dp"
      />

</RelativeLayout>

和消息

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent" android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_alignParentLeft="true"
        android:id="@+id/message_user"
        android:textStyle="normal|bold" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/message_user"
        android:layout_alignParentRight="true"
        android:id="@+id/message_time" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/message_user"
        android:layout_alignParentLeft="true"
        android:layout_marginTop="5dp"
        android:id="@+id/message_text"
        android:textAppearance="@style/TextAppearance.AppCompat.Body1"
        android:textSize="18sp" />
</RelativeLayout>

displayChatMessages是我希望适配器在我的列表中显示数据内容的位置。（将数据推送到数据库确实有效）这是我的数据库的模型。（没有孩子） enter image description here

Answer 1

必须按以下方式初始化适配器：

@Override
protected void onStart() {
    super.onStart();
    adapter.startListening();
}


@Override
protected void onStop() {
    super.onStop();
    adapter.stopListening();
}

在FirebaseListAdapter中显示Firebase数据库内容

1 个答案: