Android学习之消息框_消息 layout-优快云博客

本文是Android学习系列，讲解如何创建并实现一个带有ListView、EditText和Button的对话框。通过分析效果图，逐步解析Step1至Step5的实现过程，包括布局文件、Msg类的定义、MsgAdapter的重写等关键步骤。文章最后提供了源码下载链接。

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/**
*@author StormMaybin
*@Date 2016-06-17
*/

写在前面

每一个成功者都有一个开始。勇于开始，才能找到成功的路。

在上一篇自定义View的博客中，列举了大致的自定义View方法步骤，今天这篇博客是关于第一行代码中对话框的实现，先看一下效果图。这里写图片描述，先分析一下效果图，图中控件都有List View、EditText、和Button。下面就开始一步一步实现这个效果图。

Step1：

先在主布局文件中添加需要的控件：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:background="#d8e0e8">
    <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>

布局文件很简单，在此就不做分析了！然后新建一个xml文件来做List View的单个列表加载项。

Step2：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="10dp"
    >
    <LinearLayout
        android:id="@+id/left_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="20dp"
        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:textSize="18sp"
            android:textColor="#000000"
            />
    </LinearLayout>
    <LinearLayout
        android:id="@+id/right_layout"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="right"
        android:layout_marginRight="20dp"
        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:textSize="18sp"
            android:layout_margin="10dp"
            />
    </LinearLayout>
</LinearLayout>

Step3：

定义一个Msg类

package com.stormmaybin.androidmessagedemo;



/**
 * Created by StormMaybin on 2016/6/17.
 */
public class Msg
{
    //定义两个静态常量标志着消息类型
    public static final int TYPE_RECEIVED = 0;
    public static final int TYPE_SEND = 1;

    private String content;
    private int type;

    public Msg(String content, int type)
    {
        this.content = content;
        this.type = type;
    }

    public String getContent()
    {
        return content;
    }
    public int getType()
    {
        return type;
    }

}

Step4：

然后新建一个MsgAdapter继承ArrayAdapter，重写父类的getView方法

package com.stormmaybin.androidmessagedemo;

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;

import java.util.List;

/**
 * Created by StormMaybin on 2016/6/17.
 */
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)
    {
        //获得Msg实例
        Msg msg = getItem(position);
        View view;
        ViewHolder viewHolder;
        //开始进行判断
        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();
        }
        //如果是接收的消息，那么显示左边布局，隐藏右边的布局
        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_SEND)
        {
            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;
    }
}

Step5：

package com.stormmaybin.androidmessagedemo;


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

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

public class MainActivity extends Activity
{
    private ListView msgListView;
    private EditText inputText;
    private Button send;
    private MsgAdapter adapter;
    //定义一个容器
    private List<Msg> msgList = new ArrayList<Msg>();

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //先进行初始化
        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 View.OnClickListener()
        {
            @Override
            public void onClick(View v)
            {
                String content = inputText.getText().toString();
                if (!"".equals(content))
                {
                    Msg msg = new Msg(content , Msg.TYPE_SEND);
                    msgList.add(msg);
                    //刷新适配器
                    adapter.notifyDataSetChanged();
                    //将ListView定位到最后一行
                    msgListView.setSelection(msgList.size());
                    //清空输入框的内容
                    inputText.setText("");
                }
            }
        });
    }
    private void initMsgs()
    {
        Msg msg1 = new Msg("Hello StormMa",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 Jack, nice talking with you",Msg.TYPE_RECEIVED);
        msgList.add(msg3);
    }
}