UI

mainactivity
package com.example.uibestpracte;

import java.util.ArrayList;
import java.util.List;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.Window;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ListView;

public class MainActivity extends Activity
{
	private ListView msgListView;
	private EditText inputText;
	private Button send;
	private MsgAdapter adapter;
	private List<Msg>msgList = new ArrayList<Msg>();

	@Override
	protected void onCreate(Bundle savedInstanceState)
	{
		super.onCreate(savedInstanceState);
		requestWindowFeature(Window.FEATURE_NO_TITLE);
		setContentView(R.layout.activity_main);
		initMsgs();
		adapter = new MsgAdapter(MainActivity.this,R.layout.msg_item,msgList);
		inputText = (EditText)findViewById(R.id.input_text);
		send = (Button)findViewById(R.id.send);
		msgListView = (ListView)findViewById(R.id.msg_list_view);
		msgListView.setAdapter(adapter);
		send.setOnClickListener(new OnClickListener()
		{
			@Override
			public void onClick(View v)
			{
				String content = inputText.getText().toString();
				if(!"".equals(content))
				{
					Msg msg = new Msg(content,Msg.TYPE_SENT);
					msgList.add(msg);
					adapter.notifyDataSetChanged();
					msgListView.setSelection(msgList.size());
					inputText.setText("");
				}
			}
		});
	}
	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_SENT);
		msgList.add(msg2);
		Msg msg3 = new Msg("This is Tom,Nice talking to you.",Msg.TYPE_RECEIVED);
		msgList.add(msg3);
	}


	}
MsgAdapter
package com.example.uibestpracte;

import java.util.List;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.LinearLayout;
import android.widget.TextView;

public class MsgAdapter extends ArrayAdapter<Msg>
{
	private int resourceId;
	public MsgAdapter(Context context,int textViewResourceId,List<Msg>objects){
		super(context,textViewResourceId,objects);
		resourceId = textViewResourceId;

	}
	@Override
	public View getView(int position,View convertView,ViewGroup parent){
		Msg msg = getItem(position);
		View view;
		ViewHolder viewHolder;
		if (convertView == null){
			view = LayoutInflater.from(getContext()).inflate(resourceId,null);
			viewHolder = new ViewHolder();
			viewHolder.leftLayout = (LinearLayout) view.findViewById(R.id.left_layout);
			viewHolder.rightLayout = (LinearLayout) view.findViewById(R.id.right_layout);
			viewHolder.leftMsg = (TextView)view.findViewById(R.id.left_msg);
			viewHolder.rightMsg = (TextView)view.findViewById(R.id.right_msg);
			view.setTag(viewHolder);
		}else{
			view = convertView;
			viewHolder = (ViewHolder)view.getTag();
		}
		if(msg.getType() == Msg.TYPE_RECEIVED){
			viewHolder.leftLayout.setVisibility(View.VISIBLE);
			viewHolder.rightLayout.setVisibility(View.GONE);
			viewHolder.leftMsg.setText(msg.getContent());
		}else if(msg.getType() == Msg.TYPE_SENT){
			viewHolder.rightLayout.setVisibility(View.VISIBLE);
			viewHolder.leftLayout.setVisibility(View.GONE);
			viewHolder.rightMsg.setText(msg.getContent());
		}
		return view;
	}
	class ViewHolder{
		LinearLayout leftLayout;
		LinearLayout rightLayout;
		TextView leftMsg;
		TextView rightMsg;
	}

}

activity_main
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="#d8e0e8"
    android:orientation="vertical" >

    <ListView
        android:id="@+id/msg_list_view"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:divider="#0000" >
    </ListView>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content" >

        <EditText
            android:id="@+id/input_text"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:hint="Type something here"
            android:maxLines="2" />

        <Button
            android:id="@+id/send"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Send" />
    </LinearLayout>

</LinearLayout>
msg_item
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:padding="10dp" >
    
    
    <LinearLayout 
        android:id="@+id/left_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="left"
        android:background="@drawable/message_left">
        <TextView
            android:id="@+id/left_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_margin="10dp"
            android:textColor="#00bfff"/>
        
    </LinearLayout>
    
    <LinearLayout 
        android:id="@+id/right_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:background="@drawable/message_right">
        
        <TextView 
            android:id="@+id/right_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_margin="10dp"/>
    </LinearLayout>
   

</LinearLayout>

我觉得换个颜色比好好看

他不理我，我不是很高兴