《第一行代码Android》学习总结第三章编写聊天界面实践

1、用通过Nine-Patch制作好的气泡图片作为图片资源。

2、在app/build.gradle中添加依赖库，使用RecyclerView。

compile 'com.android.support:recyclerview-v7:26.0.0-alpha1'

3、编写activity_main.xml文件，放置用于显示聊天内容界面，EditText用于输入消息，Button用于输入消息。

4、创建Msg消息实体类

public class Msg {    public static final int TYPE_RECEIVED = 0;    public static final int TYPE_SENT = 1;    private  String content;    //消息内容    private int type;           //消息类型    public Msg(String content, int type) {        this.content = content;        this.type = type;    }    public String getContent() {        return content;    }    public int getType() {        return type;    }}

5、编写RecyclerView子项布局msg_item.xml，让收到的消息左对齐，发出的消息右对齐。

6、新建适配器类MsgAdapter类

public class MsgAdapter extends RecyclerView.Adapter {    private List mMsgList;    static class ViewHolder extends RecyclerView.ViewHolder{        LinearLayout leftLayout;        LinearLayout rightLayout;        TextView leftMsg;        TextView rightMsg;        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_mes);            rightMsg = view.findViewById(R.id.right_mes);        }    }    public MsgAdapter(List mMsgList) {        this.mMsgList = mMsgList;    }    @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);    }    @Override    public void onBindViewHolder(ViewHolder holder, int position) {          Msg msg = mMsgList.get(position);//消息类型判断，如果收到消息，则显示左边消息布局，隐藏右边消息布局//如果发出消息，则显示右边消息布局，隐藏左边消息布局          if(msg.getType() == msg.TYPE_RECEIVED){              holder.leftLayout.setVisibility(View.VISIBLE);              holder.rightLayout.setVisibility(View.GONE);              holder.leftMsg.setText(msg.getContent());          }        else if(msg.getType() == msg.TYPE_SENT){              holder.rightLayout.setVisibility(View.VISIBLE);              holder.leftLayout.setVisibility(View.GONE);              holder.rightMsg.setText(msg.getContent());          }    }    @Override    public int getItemCount() {        return mMsgList.size();    }}

7、编写MainActivity.java中代码

public class MainActivity extends AppCompatActivity {    private List msgList = new ArrayList<>();    private EditText inputText;    private Button send;    private RecyclerView msgRecyclerView;    private MsgAdapter adapter;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        initMsg();        inputText = (EditText) findViewById(R.id.input_text);        send = (Button) findViewById(R.id.send);        msgRecyclerView = (RecyclerView) findViewById(R.id.msg_recycler_view);        LinearLayoutManager layoutManager = new LinearLayoutManager(this);        msgRecyclerView.setLayoutManager(layoutManager);        adapter=new MsgAdapter(msgList);        msgRecyclerView.setAdapter(adapter);        send.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                String content = inputText.getText().toString();//如果输入消息不为空，创建新的Msg对象加入到msgList中                if(!"".equals(content)){                    Msg msg=new Msg(content,Msg.TYPE_SENT);                    msgList.add(msg);//当有新消息时，通知列表有新数据加入，刷新RecyclerView中的显示                    adapter.notifyItemInserted(msgList.size()-1);//将显示的数据定位到最后一行，保证一定能看到最后发出的一行数据                    msgRecyclerView.scrollToPosition(msgList.size()-1);                    inputText.setText("");                }            }        });    }//创建消息数据    private void initMsg() {        Msg msg1 = new Msg("Hello Guys" ,Msg.TYPE_RECEIVED);        msgList.add(msg1);        Msg msg2 = new Msg("Who is that" ,Msg.TYPE_SENT);        msgList.add(msg2);        Msg msg3 = new Msg("This is Tom" ,Msg.TYPE_RECEIVED);        msgList.add(msg3);    }}

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