编写聊天界面的最佳实践
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1、编写主界面,activity_main.xml:
- 使用总线性布局,在总线性布局里包含了一个ListView控件和另一个LinearLayout。
- 在垂直方向上,LinearLayout按照wrap_content来计算,剩下的空间是ListView控件的,( android:layout_weight="1")
- LinearLayout里边包含一个EditText控件和一个按钮控件。按钮控件按照wrap_content来计算,剩下的空间是EditText控件的(android:layout_weight="1")
<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" > <!-- ListView 占下剩余的空间 --> <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>
2、编写消息的实体类
package com.example.uibestpractice; public class Msg { public static final int TYPE_RECEIVED=0; //接受一条消息 public static final int TYPE_SENT=1; //发送一条消息 private String content; //消息的内容 private int type; //消息的类型 public Msg(String content, int type) { this.content = content; this.type = type; } public String getContent() { return content; } public int getType() { return type; } }
3、编写ListView子项的布局:msg_item.xml
LinearLayout里边又包含了两个线性布局分别为LinearLayout1和LinearLayout2.一个为左布局,一个为右。在后面中,可以控制控件的可见性,来区别消息是发送还是接收。
<?xml version="1.0" encoding="utf-8"?> <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="#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/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>
4、创建ListView的适配器
package com.example.uibestpractice; 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); // TODO Auto-generated constructor stub resourceID=textViewResourceId; } @Override public View getView(int position, View convertView, ViewGroup parent) { // TODO Auto-generated method stub 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){//如果是收到的消息,则设置显示左边的消息布局,将右边的布局隐藏 viewHolder.leftLayout.setVisibility(View.VISIBLE); viewHolder.rightLayout.setVisibility(View.GONE); viewHolder.leftMsg.setText(msg.getContent()); }else if(msg.getType()==Msg.TYPE_SENT){ viewHolder.leftLayout.setVisibility(View.GONE); viewHolder.rightLayout.setVisibility(View.VISIBLE); viewHolder.rightMsg.setText(msg.getContent()); } return view; } class ViewHolder{ LinearLayout leftLayout; LinearLayout rightLayout; TextView leftMsg; TextView rightMsg; } }
5、最后修改MainActivity.java
package com.example.uibestpractice; import java.util.ArrayList; import java.util.List; import android.os.Bundle; import android.app.Activity; import android.view.Menu; import android.view.View; import android.view.View.OnClickListener; 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 msgAdapter; private List<Msg> msgList=new ArrayList<Msg>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); initMsgs(); msgAdapter=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(msgAdapter); send.setOnClickListener(new OnClickListener() { @Override public void onClick(View arg0) { // TODO Auto-generated method stub String content=inputText.getText().toString(); if(!"".equals(content)){ Msg msg=new Msg(content,Msg.TYPE_SENT); msgList.add(msg); msgAdapter.notifyDataSetChanged();//当有新消息时,刷新ListView中显示 msgListView.setSelection(msgList.size());//将ListView定位到最后一行。 inputText.setText("");//清空输入框中的内容 } } }); } 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); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.main, menu); return true; } }
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