android小技巧实现聊天窗口

第一步添加聊天界面

<?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:background="#d8e0e8"
    android:layout_height="match_parent">

    <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="编写"
            android:maxLines="2"/>
        <Button
            android:id="@+id/send"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="发送"/>
        </LinearLayout>
</LinearLayout>

 

第二步添加消息实体

public class Msg {
    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;
    }
}

第三步添加ListView的子项布局

<?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_gravity="left"
        android:background="@drawable/two9">

        <TextView
            android:id="@+id/left_msg"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="center"
            android:layout_margin="20dp"
            android:textColor="#fff"/>
        </LinearLayout>

    <LinearLayout
            android:id="@+id/right_layout"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_gravity="right"
            android:background="@drawable/two9"
            >
            <TextView
                android:id="@+id/right_msg"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
                android:layout_margin="30dp"/>
            </LinearLayout>
</LinearLayout>

 

第四步添加适配器

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){
        if(convertView==null)
        {
            convertView= LayoutInflater.from(getContext()).inflate(resourceId, null);
        }
        Msg msg=getItem(position);//获取当前项的Msg实例
        if (msg.getType()==Msg.TYPE_RECEIVED)
        {
            ViewHolderExt.get(convertView,R.id.left_layout).setVisibility(View.VISIBLE);
            ViewHolderExt.get(convertView,R.id.right_layout).setVisibility(View.GONE);
            ((TextView)ViewHolderExt.get(convertView,R.id.left_msg)).setText(msg.getContent());
        }
        else if(msg.getType()==Msg.TYPE_SEND)
        {
            ViewHolderExt.get(convertView,R.id.right_layout).setVisibility(View.VISIBLE);
            ViewHolderExt.get(convertView,R.id.left_layout).setVisibility(View.GONE);
            ((TextView)ViewHolderExt.get(convertView,R.id.right_msg)).setText(msg.getContent());
        }
        return  convertView;
    }
}

其中ViewHolderExt是一个通用类，用于缓存每个View下对应的子view，这样在返回时不用再继续找每个子View,提高效率。

//高度抽象的ViewHolder
public  class  ViewHolderExt{
    @SuppressWarnings("unchecked")
    public static  <T extends View> T get(View view,int id){
        SparseArray<View> viewHolder=(SparseArray<View>)view.getTag();
        if(viewHolder==null)
        {
            viewHolder=new SparseArray<View>();
            view.setTag(viewHolder);
        }
        View childView=viewHolder.get(id);
        if(childView==null){
            childView=view.findViewById(id);
            viewHolder.put(id,childView);
        }
        return  (T)childView;
    }
}

第五步添加界面代码和公共缓存器

public class MsgActivity 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);
        setContentView(R.layout.ui_talk);
        initMsgs();
        adapter=new MsgAdapter(MsgActivity.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);
                    adapter.notifyDataSetChanged();//有新消息刷新
                    msgListView.setSelection(msgList.size());//选择最后一条
                    inputText.setText("");
                }
            }
        });
    }

    private void initMsgs(){
        Msg msg1=new Msg("hello guy.",Msg.TYPE_RECEIVED);
        msgList.add(msg1);
        Msg msg2=new Msg("你好。你是谁？",Msg.TYPE_SEND);
        msgList.add(msg2);
        Msg msg3=new Msg("this is Tom. Nice talking to you.",Msg.TYPE_RECEIVED);
        msgList.add(msg3);
    }
}