一个用于大量数据展示的新控件RecylerView，可以用来代替传统的ListView，更加强大和灵活。可以实现横向滚动（ListView做不到）和瀑布流控件。
使用RecyclerView编写一个聊天界面- 在app/build.gradle中添加依赖（RecyclerView在AndroidX包里）
//实现RecyclerView要添加依赖
implementation 'androidx.recyclerview:recyclerview:1.0.0'
2.编写主界面activity_chat.xml中的代码
界面效果图：
- 定义消息的实体类，新建Msg
package com.example.networktest;
public class Msg {
static final int TYPE_RECEIVED = 0;//表示一条收到的消息
static final int TYPE_SEND = 1;//表示一条发出的消息
private String content;//表示消息内容
private int type;//表示消息的类型
public String getContent() {
return content;
}
public void setContent(String content) {
this.content = content;
}
public int getType() {
return type;
}
public void setType(int type) {
this.type = type;
}
public Msg(String content, int type) {
this.content = content;
this.type = type;
}
}
- 编写RecyclerView子项的布局，新建msg_item.xml
界面效果图：
- 创建RecyclerView的适配器类，新建类MsgAdapter
package com.example.networktest; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.LinearLayout; import android.widget.TextView; import androidx.annotation.NonNull; import androidx.recyclerview.widget.RecyclerView; import java.util.List; public class MsgAdapter extends RecyclerView.Adapter{ private List mMsgList; static class ViewHolder extends RecyclerView.ViewHolder { LinearLayout leftLayout;//做边子项布局 LinearLayout rightLayout;//右边子项布局 TextView leftMsg;//左边消息（接收） TextView rightMSg;//右边消息（发送） //绑定item控件 public ViewHolder(View view) { super(view); leftLayout = view.findViewById(R.id.left_layout); rightLayout = view.findViewById(R.id.right_layout); leftMsg = view.findViewById(R.id.left_msg); rightMSg = view.findViewById(R.id.right_msg); } } //绑定 数据 public MsgAdapter(List msgList) { mMsgList = msgList; } //绑定 显示页面 // onCreateViewHolder 用于创建一个ViewHolder实例 @Override public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) { View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.msg_item, parent, false); return new ViewHolder(view); } //对消息类型的判断 //onBindViewHolder 用于对RecyclerView子项的数据进行赋值的 @Override public void onBindViewHolder(ViewHolder holder, int position) { //获得 当前的Msg实例 Msg msg = mMsgList.get(position); //如果是 收到的消息，则显示左边的消息布局，将右边的消息布局隐藏 if (msg.getType() == Msg.TYPE_RECEIVED) { holder.leftLayout.setVisibility(View.VISIBLE); holder.rightLayout.setVisibility(View.GONE); //消息内容 holder.leftMsg.setText(msg.getContent()); } else if (msg.getType() == Msg.TYPE_SEND) { //如果是 发出的消息，则显示右边的消息布局，将左边的消息布局隐藏 holder.rightLayout.setVisibility(View.VISIBLE); holder.leftLayout.setVisibility(View.GONE); //消息内容 holder.rightMSg.setText(msg.getContent()); } } //获取 RecyclerView一共有多少子项 @Override public int getItemCount() { return mMsgList.size(); } }
- 编写ChatActivity.java,为RecyclerView初始化数据，并给发送按钮加入事件响应
package com.example.networktest;
import androidx.appcompat.app.AppCompatActivity;
import androidx.appcompat.widget.Toolbar;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.LinearLayout;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
public class ChatActivity extends AppCompatActivity {
private Toolbar tool_bar_setting;
private List msgList = new ArrayList<>();
private EditText inputText;//文本输入框
private Button send;//发送按钮
private RecyclerView msgRecyclerView;
private MsgAdapter mAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_chat);
init();
initMsgs();
listen();
}
private void init() {
//绑定 Toolbar
tool_bar_setting = findViewById(R.id.tool_bar_setting);
//得到toolBar实例
setSupportActionBar(tool_bar_setting);
//显示 tool_bar左侧按钮
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
// setSupportActionBar(toolbar);参数报错
// Android Studio 自动导包错误
// import android.widget.Toolbar;
// 将上面的代码替换成下面的
// import androidx.appcompat.widget.Toolbar;
inputText = findViewById(R.id.inputText);
send = findViewById(R.id.send);
msgRecyclerView = findViewById(R.id.msg_recycler_view);
LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
msgRecyclerView.setLayoutManager(linearLayoutManager);
//给适配器绑定数据
mAdapter = new MsgAdapter(msgList);
//给RecyclerView控件绑定适配器
msgRecyclerView.setAdapter(mAdapter);
}
private void listen() {
send.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String content = inputText.getText().toString();
//发送内容不为空时
if (!"".equals(content)) {
//将数据传入实体类
Msg msg = new Msg(content, Msg.TYPE_SEND);
msgList.add(msg);
//有新消息时刷新msgRecyclerView
mAdapter.notifyItemInserted(msgList.size() - 1);
//将 RecyclerView 定位到最后一行,以保证可以看到最后发出的一条消息
msgRecyclerView.scrollToPosition(msgList.size()-1);
//发送完 清空输入框中的内容
inputText.setText("");
}
}
});
}
//初始化几条 接收到的消息（毕竟是个没有联网的聊天界面）
private void initMsgs() {
Msg msg1 = new Msg("hello guy.", Msg.TYPE_RECEIVED);
msgList.add(msg1);
Msg msg2 = new Msg("hello. Who is that ?", Msg.TYPE_SEND);
msgList.add(msg2);
Msg msg3 = new Msg("This is Tom.Nice talking to you.", Msg.TYPE_RECEIVED);
msgList.add(msg3);
}
//加载 toorlbar.xml这个菜单文件
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.tool_bar_setting, menu);
return true;
}
//处理多个按钮的点击事件
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
Intent intent = new Intent(ChatActivity.this, MainActivity.class);
startActivity(intent);
finish();
break;
case R.id.love_setting:
Toast.makeText(this, "you clicked love", Toast.LENGTH_SHORT).show();
break;
}
return true;
}
}
真机运行效果图：
