FirebaseListAdapter 不为聊天应用推送单个项目 - Firebase-Ui 3.1 [英] FirebaseListAdapter not pushing individual items for chat app - Firebase-Ui 3.1

问题描述

我正在 Android 上制作一个聊天应用程序，它使用 google firebase 来存储用户相互写的消息.为了向用户显示这些消息，我从数据库中读取它们并将它们组织成一个带有 ListAdapter 的自定义 ListView.这一切正常，直到我更新了我的依赖项，特别是 firebase ui:

com.firebaseui:firebase-ui:3.1.0

现在构造列表适配器的代码不起作用，是:

adapter = new FirebaseListAdapter(FirebaseDatabase.getInstance().getReference("Lobbies").child(leaderID).child("Messages"), ChatMessage.class, R.layout.message, this){@覆盖protected void populateView(View v, ChatMessage model, int position) {//获取对 message.xml 视图的引用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);//设置他们的文本messageText.setText(model.getMessageText());messageUser.setText(model.getMessageUser());//在显示之前格式化日期messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)",模型.getMessageTime()));}};

为了解决这个问题，我更新了代码以符合新的 firebase ui 要求，使代码变成:

FirebaseListOptionsoptions = new FirebaseListOptions.Builder().setQuery(FirebaseDatabase.getInstance().getReference("Lobbies").child(leaderID).child("Messages"), ChatMessage.class).setLayout(R.layout.message).build();适配器 = 新 FirebaseListAdapter(选项){@覆盖protected void populateView(View v, ChatMessage model, int position) {//获取对 message.xml 视图的引用TextView messageText = v.findViewById(R.id.message_text);TextView messageUser = v.findViewById(R.id.message_user);TextView messageTime = v.findViewById(R.id.message_time);//设置他们的文本messageText.setText(model.getMessageText());messageUser.setText(model.getMessageUser());//在显示之前格式化日期messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)",模型.getMessageTime()));}};

此代码现在可以正常编译，但列表视图未显示数据.是否有特定的正确方法可以使用新的 firebase ui 依赖项来制作列表适配器?

解决方案

让 FirebaseRecyclerAdapter 和 FirebaseListAdapter 显示活动数据

你需要使用这个:

@Override受保护的无效 onStart() {super.onStart();适配器.startListening();}@覆盖受保护的无效 onStop() {super.onStop();适配器.stopListening();}

由于 FirebaseListAdapter 使用侦听器来检查 firebase 数据库中的更改，因此要侦听数据，您需要在 adapter.startListening() 中添加 adapter.startListening()>onStart() 能够在列表视图中显示数据.

然后在 onStop() 内部(当活动停止时)，您可以使用 adapter.stopListening() 删除监听器和适配器中的数据.>

查看更多信息:适配器生命周期

注意:

如果使用上述方法后，您得到nullpointexception 或cannot resolve symbol，则必须将adapter 声明为全局变量并请检查以下答案:startListening() 中的错误

I am making a chat app on Android that uses google firebase to store messages that users write to each other. To display these messages to the users I read them from the database and organize them into a custom ListView with a ListAdapter. This was working fine until I updated my dependencies, specifically firebase ui to:

com.firebaseui:firebase-ui:3.1.0

Now the code to construct the list adapter does not work, being:

adapter = new FirebaseListAdapter<ChatMessage>(FirebaseDatabase.getInstance().getReference("Lobbies").child(leaderID).child("Messages"), ChatMessage.class, R.layout.message, this) {
        @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());

            // Format the date before showing it
            messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)",
                    model.getMessageTime()));
        }
    };

To fix this issue, I updated the code to conform to the new firebase ui requirements, making the code become:

FirebaseListOptions<ChatMessage> options = new FirebaseListOptions.Builder<ChatMessage>()
            .setQuery(FirebaseDatabase.getInstance().getReference("Lobbies").child(leaderID).child("Messages"), 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 = v.findViewById(R.id.message_text);
            TextView messageUser = v.findViewById(R.id.message_user);
            TextView messageTime = v.findViewById(R.id.message_time);

            // Set their text
            messageText.setText(model.getMessageText());
            messageUser.setText(model.getMessageUser());

            // Format the date before showing it
            messageTime.setText(DateFormat.format("dd-MM-yyyy (HH:mm:ss)",
                    model.getMessageTime()));
        }
    };

This code compiles fine now, but the listview is not displaying the data. Is there a specific right way to use the new firebase ui dependency to make the list adapter?

解决方案

To let the FirebaseRecyclerAdapter and FirebaseListAdapter show the data on the activity

You need to use this:

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


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

Since FirebaseListAdapter uses a listener to check for changes in the firebase database, then to being listening for data you need to add adapter.startListening() inside the onStart() to be able to show the data in the listview.

Then inside onStop() (when activity is stopped), you can use adapter.stopListening() to remove the listener and the data in the adapter.

Check this for more info: Adapter LifeCycle

Note:

If after using the above, you get a nullpointexception or cannot resolve symbol, you have to declare adapter as global variable and please check the below answer: Error in startListening()

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