如何为传入和传出的聊天消息使用不同的布局

Question

我有一个消息设计。 2个xml文件负责设计：

recyclerview_item_incoming.xml
recyclerview_item_outgoing.xml

看起来像这样：

消息存储在RecyclerView 中。 RecyclerView 通过 LiveData -> Room 连接到 SQLite。 More Info

要使用 RecyclerView，我有 2 个类：

MessageListAdapter：

package com.mardaunt.telesupp.recyclerview;

import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.DiffUtil;
import androidx.recyclerview.widget.ListAdapter;

import com.mardaunt.telesupp.room.Message;

public class MessageListAdapter extends ListAdapter<Message, MessageViewHolder> {

    public static int idMessage = 0; // I added that
    public static int countMessages = 0; // I added that

    public MessageListAdapter(@NonNull DiffUtil.ItemCallback<Message> diffCallback) {
        super(diffCallback);
    }

    @Override
    public MessageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        countMessages = getItemCount();
        //System.out.println(countMessages + " - This countMessages\n" + idMessage + "- This idMessage; " + viewType + " - viewType");
        System.out.println(idMessage);
        //if(idMessage >= countMessages) idMessage = 0;
        // I need to pass the create index method of the current message.!!!!!!!!!!
        // The getItem() function returns a Message object.
        return MessageViewHolder.create(parent, getItem(idMessage));
    }

    @Override
    public void onBindViewHolder(MessageViewHolder holder, int position) {
        Message current = getItem(position);
        //System.out.println(current.getId() + " " + current.getPhone() + " " + current.getText());
        holder.bind(current.getPhone() ,current.getText()); // Бинтим только тело телефон и сообщение!
        idMessage = position+1;
        if(idMessage >= countMessages) idMessage = 0;
    }

    public static class MessageDiff extends DiffUtil.ItemCallback<Message> {

        @Override
        public boolean areItemsTheSame(@NonNull Message oldItem, @NonNull Message newItem) {
            return oldItem == newItem;
        }

        @Override
        public boolean areContentsTheSame(@NonNull Message oldItem, @NonNull Message newItem) {
            return oldItem.getText().equals(newItem.getText());
        }
    }
}

MessageViewHolder：

package com.mardaunt.telesupp.recyclerview;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import androidx.recyclerview.widget.RecyclerView;

import com.mardaunt.telesupp.R;
import com.mardaunt.telesupp.room.Message;

class MessageViewHolder extends RecyclerView.ViewHolder {
    private final TextView phoneItemView;
    private final TextView messageItemView;

    private MessageViewHolder(View itemView) {
        super(itemView);
        messageItemView = itemView.findViewById(R.id.text_view_message);
        phoneItemView = itemView.findViewById(R.id.text_view_phone);
    }

    public void bind(String phone, String message) {
        phoneItemView.setText(phone);
        messageItemView.setText(message);
    }

        //The method decides which design to choose for the message bubble.
    static MessageViewHolder create(ViewGroup parent, Message current) {
        View view;
        if (current.getNature().equals("outgoing"))
            view = LayoutInflater.from(parent.getContext())
                    .inflate(R.layout.recyclerview_item_outgoing, parent, false);
        else view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.recyclerview_item_incoming, parent, false);
        return new MessageViewHolder(view);
    }
}

和消息：

package com.mardaunt.telesupp.room;

import androidx.annotation.NonNull;
import androidx.room.Entity;
import androidx.room.PrimaryKey;

@Entity(tableName = "messages_table")
public class Message {

    @PrimaryKey(autoGenerate = true)
    private int id;
    private String phone;
    private String text;
    private String nature;

    public Message(int id,
                   @NonNull String phone,
                   @NonNull String text,
                   @NonNull String nature
                    ) {
        this.id = id;
        this.phone = phone;
        this.text = text;
        this.nature = nature; // incoming OR outgoing
    }

    public int getId(){return this.id;}
    public String getPhone(){return this.phone;}
    public String getText(){return this.text;}
    public String getNature(){return this.nature;}
}

问题： 我希望传入的消息位于左侧。传出消息位于右侧。 为此，我稍微更改了MessageViewHolder 类的静态方法：

 //The method decides which design to choose for the message bubble.
static MessageViewHolder create(ViewGroup parent, Message current) {
    View view;
    if (current.getNature().equals("outgoing"))
        view = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.recyclerview_item_outgoing, parent, false);
    else view = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.recyclerview_item_incoming, parent, false);
    return new MessageViewHolder(view);
}

但问题是我不知道如何正确地将 Message 对象传递给此方法？ 如您所见，我尝试在MessageListAdapter 类中传递Message 对象：

@Override
public MessageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    countMessages = getItemCount();
    // I need to pass the create index method of the current message.!!!!!!!!!!
    // The getItem() function returns a Message object.
    return MessageViewHolder.create(parent, getItem(idMessage));
}

@Override
public void onBindViewHolder(MessageViewHolder holder, int position) {
    Message current = getItem(position);
    holder.bind(current.getPhone() ,current.getText()); // Бинтим только тело телефон и сообщение!
    idMessage = position+1;
    if(idMessage >= countMessages) idMessage = 0;
}

我添加了 2 个静态变量（idMessage、countMessages），但这不能正常工作。 如何为方法 MessageViewHolder.create(...) 添加 Message 对象？

GitHub 上的项目：https://github.com/MinorityMeaning/HelloApp

Answer 1

getItemViewType() 是确定项目布局的正确位置。所以你需要把逻辑移到那里，所以在适配器中覆盖它：

@Override
public int getItemViewType(int position) {
    if (getItem(position).getNature().equals("outgoing"))
        return R.layout.recyclerview_item_outgoing;
    else
        return R.layout.recyclerview_item_incoming;
}

这反映在onCreateViewHolder() 的viewType 参数中，因此它拥有当前项目的正确布局。因此，您可以将其传递给 ViewHolder：

@Override
public MessageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    return MessageViewHolder.create(parent, viewType);
}

在 ViewHolder 中将其设置为您的布局：

static MessageViewHolder create(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext())
            .inflate(viewType, parent, false);
    return new MessageViewHolder(view);
}