Question

我正在关注this教程来创建聊天应用。这是我的displayChatMessages()方法：

ListView listOfMessages = (ListView)findViewById(R.id.list_of_messages);

    adapter = new FirebaseListAdapter<ChatMessages>(this, ChatMessages.class, R.layout.message, FirebaseDatabase.getInstance().getReference()) {
        @Override
        protected void populateView(View v, ChatMessages model, int position) {
            // Get references to the views of message.xml
            TextView messageText = (TextView)v.findViewById(R.id.message_text);
            TextView messageTime = (TextView)v.findViewById(R.id.message_time);

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

    listOfMessages.setAdapter(adapter);

但是我在这部分得到了一个红色下划线：

(this, ChatMessages.class, R.layout.message, FirebaseDatabase.getInstance().getReference())

Android Studio说

Firebaselistadapter中的
Firebaselistadapter()无法应用于...

更新：这是错误消息：

错误：（76,19）错误：类FirebaseListAdapter中的构造函数FirebaseListAdapter无法应用于给定类型; 必需：FirebaseListOptions 发现：MainActivity，Class，int，DatabaseReference 原因：实际和正式的参数列表长度不同其中T是一个类型变量： T扩展了类FirebaseListAdapter中声明的Object

Answer 1

感谢您提供完整的错误消息 - 这有很大帮助。基于此，我认为这是你需要做的。

//Suppose you want to retrieve "chats" in your Firebase DB:
Query query = FirebaseDatabase.getInstance().getReference().child("chats");
//The error said the constructor expected FirebaseListOptions - here you create them:
FirebaseListOptions<ChatMessage> options = new FirebaseListOptions.Builder<ChatMessage>()
                    .setQuery(query, ChatMessages.class)
                     .setLayout(android.R.layout.message)
                    .build();
    //Finally you pass them to the constructor here:                
 adapter = new FirebaseListAdapter<ChatMessages>(options){
    @Override
    protected void populateView(View v, ChatMessages model, int position) {
        // Get references to the views of message.xml
        TextView messageText = (TextView)v.findViewById(R.id.message_text);
        TextView messageTime = (TextView)v.findViewById(R.id.message_time);

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

这是遇到同样问题的article。

Answer 2

如错误所示，您需要FirebaseListOptions，请使用此处：

Query query=FirebaseDatabase.getInstance().getReference().orderByChild("name").equalTo(name);
FirebaseListOptions<ChatMessages> options = new FirebaseListOptions.Builder<ChatMessages>()
    .setQuery(query, ChatMessages.class)
    .build();

FirebaseListAdapter<ChatMessages> adapter = new FirebaseListAdapter<ChatMessages>(options) {
@Override
protected void populateView(View v, ChatMessages model, int position) {
    //code here

 }
};

FirebaseListAdapter＆LT;＆GT;不工作

2 个答案: