为什么我的 RecyclerView 不显示任何内容？

问题描述 投票：0回答：1

背景

我正在开发一个聊天应用程序，但在使用 RecyclerView 显示内容时遇到问题。我正在使用 ViewBinding。

这是我面临的问题：尽管我做出了努力，RecyclerView 仍不显示任何内容。我已经实现了 ViewBinding 来绑定视图，但我不确定是什么导致了这个问题。

我的代码

这是我的代码。此外，我还按照这些视频来构建应用程序：Android 聊天应用程序开发。

在

ChatMessageAdapter.java
：

import ...
public class ChatMessageAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
    private final List<ChatMessage> chatMessageList;

    public ChatMessageAdapter(List<ChatMessage> chatMessageList) {
        this.chatMessageList = chatMessageList;
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
//        Log.d("tag", "why!!!!!!");

        if (viewType == Constants.VIEW_TYPE_SENT) {
            return new SentMassageViewHolder(
                    ItemContainerSentMessageBinding.inflate(
                            LayoutInflater.from(parent.getContext()),
                            parent,
                            false
                    )
            );
        } else {
            return new ReceivedMassageViewHolder(
                    ItemContainerReceivedMessageBinding.inflate(
                            LayoutInflater.from(parent.getContext()),
                            parent,
                            false
                    )
            );
        }

//        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_container_sent_message, parent, false);
//        return new testViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
        if (getItemViewType(position) == Constants.VIEW_TYPE_SENT) {
            ((SentMassageViewHolder) holder).setData((chatMessageList.get(position)));
        } else {
            ((ReceivedMassageViewHolder) holder).setData(chatMessageList.get(position));
        }
//        ((testViewHolder) holder).test.setText(chatMessageList.get(position).getMessage());
    }


    static class testViewHolder extends RecyclerView.ViewHolder {
        TextView test;
        public testViewHolder(@NonNull View itemView) {
            super(itemView);
            test = itemView.findViewById(R.id.textMessage);
        }
    }

    @Override
    public int getItemCount() {
        return chatMessageList.size();
    }

    @Override
    public int getItemViewType(int position) {
        return chatMessageList.get(position).getIsSent();
    }

    static class SentMassageViewHolder extends RecyclerView.ViewHolder {

        private final ItemContainerSentMessageBinding binding;

        SentMassageViewHolder(ItemContainerSentMessageBinding itemContainerSentMessageBinding) {
            super(itemContainerSentMessageBinding.getRoot());
            binding = itemContainerSentMessageBinding;
        }

        void setData(ChatMessage chatMessage) {
            binding.textDateTime.setText(chatMessage.getDateTime());
            binding.textMessage.setText(chatMessage.getMessage());
        }
    }

    static class ReceivedMassageViewHolder extends RecyclerView.ViewHolder {

        private final ItemContainerReceivedMessageBinding binding;

        ReceivedMassageViewHolder(ItemContainerReceivedMessageBinding itemContainerReceivedMessageBinding) {
            super(itemContainerReceivedMessageBinding.getRoot());
            binding = itemContainerReceivedMessageBinding;
        }

        void setData(ChatMessage chatMessage) {
            binding.textDateTime.setText(chatMessage.getDateTime());
            binding.textMessage.setText(chatMessage.getMessage());
        }
    }
}

在

ChatActivity.java
：

import ...

public class ChatActivity extends AppCompatActivity {
    private ActivityChatBinding binding;
    private List<ChatMessage> chatMessages;
    private ChatMessageAdapter chatAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        binding = ActivityChatBinding.inflate(getLayoutInflater());
        View view = binding.getRoot();
        setContentView(view);

        setListeners();
        init();
    }

    private void init() {
        LinearLayoutManager manager = new LinearLayoutManager(this);
        manager.setOrientation(RecyclerView.VERTICAL);
        binding.chatRecycleView.setLayoutManager(manager);
//        binding.chatRecycleView.smoothScrollToPosition(0);


        initMessageList();
        Log.d("In init()", chatMessages.get(0).getMessage());
//        binding.chatRecycleView.notify();
        chatAdapter = new ChatMessageAdapter(chatMessages);
        binding.chatRecycleView.setAdapter(chatAdapter);
    }

    private void initMessageList() {
        chatMessages = new ArrayList<>();
        ChatMessage msg1 = new ChatMessage("20231022", "Hello, World!", "Jobs", Constants.VIEW_TYPE_RECEIVED);
        chatMessages.add(msg1);
        ChatMessage msg2 = new ChatMessage("20231026", "Beep", "Me", Constants.VIEW_TYPE_SENT);
        chatMessages.add(msg2);
        ChatMessage msg3 = new ChatMessage("20231026", "Don't stop me now", "Jobs", Constants.VIEW_TYPE_RECEIVED);
        chatMessages.add(msg3);
    }

    private void setListeners() {
        binding.imageBack.setOnClickListener(v -> finish());

        String message = binding.inputText.getText().toString();
        binding.send.setOnClickListener(v -> {
            if (!message.equals("")) {
                chatMessages.add(new ChatMessage("20231029", message, "Me", Constants.VIEW_TYPE_SENT));
            }
        });
    }
}

在

activity_chat.xml
：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    android:animateLayoutChanges="true"
    android:background="@color/primary">

    <View
        android:id="@+id/viewBackground"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginBottom="16dp"
        android:background="@drawable/background_content_top"
        app:layout_constraintBottom_toTopOf="@id/layoutSend"
        app:layout_constraintTop_toTopOf="parent" />

    <View
        android:id="@+id/headerBackground"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:background="@color/primary"
        app:layout_constraintBottom_toTopOf="@id/viewSupporter"
        app:layout_constraintTop_toTopOf="parent" />

    <androidx.appcompat.widget.AppCompatImageView
        android:id="@+id/imageBack"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginTop="12dp"
        android:padding="5dp"
        android:src="@drawable/ic_back"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:tint="@color/white"/>

    <androidx.appcompat.widget.AppCompatImageView
        android:id="@+id/imageInfo"
        android:layout_width="30dp"
        android:layout_height="30dp"
        android:layout_marginTop="12dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:padding="4dp"
        android:src="@drawable/ic_info"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:tint="@color/white"/>

    <TextView
        android:id="@+id/textName"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginStart="8dp"
        android:layout_marginEnd="8dp"
        android:ellipsize="end"
        android:gravity="center"
        android:maxLines="1"
        android:textColor="@color/white"
        android:textSize="14sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="@id/imageBack"
        app:layout_constraintEnd_toStartOf="@id/imageInfo"
        app:layout_constraintStart_toEndOf="@id/imageBack"
        app:layout_constraintTop_toTopOf="@id/imageBack"/>

    <View
        android:id="@+id/viewSupporter"
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:layout_marginTop="12dp"
        app:layout_constraintTop_toBottomOf="@id/imageBack" />

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/chatRecycleView"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:clipToPadding="false"
        android:orientation="vertical"
        android:overScrollMode="never"
        android:padding="20dp"
        android:visibility="gone"
        app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager"
        app:layout_constraintBottom_toBottomOf="@id/viewBackground"
        app:layout_constraintTop_toBottomOf="@id/viewSupporter"/>

    <FrameLayout
        android:id="@+id/layoutSend"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_marginEnd="16dp"
        android:layout_marginRight="16dp"
        android:layout_marginBottom="12dp"
        android:background="@drawable/background_chat_input"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent">

        <androidx.appcompat.widget.AppCompatImageView
            android:id="@+id/send"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:layout_marginStart="4dp"
            android:layout_marginLeft="4dp"
            android:padding="8dp"
            android:src="@drawable/ic_send"
            app:tint="@color/white" />

    </FrameLayout>

    <EditText
        android:id="@+id/input_text"
        android:layout_width="0dp"
        android:layout_height="40dp"
        android:layout_marginStart="16dp"
        android:layout_marginLeft="16dp"
        android:layout_marginEnd="8dp"
        android:layout_marginRight="8dp"
        android:layout_marginBottom="12dp"
        android:background="@drawable/background_chat_input"
        android:hint="请输入信息"
        android:imeOptions="actionDone"
        android:importantForAutofill="no"
        android:inputType="text"
        android:paddingStart="16dp"
        android:paddingEnd="16dp"
        android:textColor="@color/white"
        android:textColorHint="#5E83AE"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toStartOf="@id/layoutSend"
        app:layout_constraintStart_toStartOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

在容器中：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:padding="4dp">

    <TextView
        android:id="@+id/textMessage"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:background="@drawable/background_sent_message"
        android:padding="12dp"
        android:textColor="@color/white"
        android:textSize="13sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintWidth_percent="0.8"/>

        <TextView
            android:id="@+id/textDateTime"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_marginTop="4dp"
            android:textColor="@color/secondary_text"
            android:textSize="10sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintTop_toBottomOf="@id/textMessage"/>

</androidx.constraintlayout.widget.ConstraintLayout>

我尝试了什么

如您所见，我尝试同时使用

binding.chatRecycleView.smoothScrollToPosition(0);
和
binding.chatRecycleView.notify();
但是问题仍然存在。

此外，

Log.d("tag", "why!!!!!!");
中添加的日志
onCreateViewHolder()
未触发。这真的让我很困惑。

您能否指导我如何解决此问题并使内容在 RecyclerView 中正确显示？非常感谢！

java android android-recyclerview
1个回答
0
投票

适配器代码看起来不错，除非我遗漏了一些东西。

我唯一能注意到的是，您已将 

RecyclerView
的可见性设置为 
gone
。

从您的 

android:visibility="gone"
中删除 
RecyclerView
。

您还可以将 

listitem
属性添加到您的 
RecyclerView
。它将在设计预览中显示 
RecyclerView
的外观，并避免此类情况。

tools:listitem="@layout/list_item_layout_of_your_reycler_view"
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