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在 Android 开发中，实现未读消息数的功能通常需要结合 RecyclerView、Adapter 和数据模型来实现。下面是一种简单的实现方式：
1. 定义消息数据模型 Message：
```java
public class Message {
private String content;
private boolean isRead;
public Message(String content, boolean isRead) {
this.content = content;
this.isRead = isRead;
}
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public boolean isRead() {
return isRead;
}
public void setRead(boolean read) {
isRead = read;
}
}
```
2. 创建 MessageAdapter 继承 RecyclerView.Adapter，并在 onBindViewHolder 方法中设置未读消息的样式：
```java
public class MessageAdapter extends RecyclerView.Adapter
private List
public MessageAdapter(List
this.messages = messages;
}
@NonNull
@Override
public MessageViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_message, parent, false);
return new MessageViewHolder(view);
}
@Override
public void onBindViewHolder(@NonNull MessageViewHolder holder, int position) {
Message message = messages.get(position);
holder.bind(message);
if (message.isRead()) {
// 已读样式
} else {
// 未读样式
}
}
@Override
public int getItemCount() {
return messages.size();
}
public static class MessageViewHolder extends RecyclerView.ViewHolder {
private TextView contentTextView;
public MessageViewHolder(@NonNull View itemView) {
super(itemView);
contentTextView = itemView.findViewById(R.id.text_content);
}
public void bind(Message message) {
contentTextView.setText(message.getContent());
}
}
}
```
3. 在主界面 Activity 中，初始化 RecyclerView 和数据源，并更新未读消息数：
```java
public class MainActivity extends AppCompatActivity {
private RecyclerView recyclerView;
private MessageAdapter adapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = findViewById(R.id.recycler_view);
recyclerView.setLayoutManager(new LinearLayoutManager(this));
List
messages.add(new Message("Hello", false));
messages.add(new Message("World", true));
adapter = new MessageAdapter(messages);
recyclerView.setAdapter(adapter);
int unreadCount = 0;
for (Message message : messages) {
if (!message.isRead()) {
unreadCount++;
}
}
setTitle("未读消息数：" + unreadCount);
}
}
```
通过以上步骤，您可以在 Android 应用中显示未读消息数，并根据消息的读取状态显示不同的样式。这样，用户就可以清晰地了解自己有多少未读消息。希望这个示例对您有帮助。
