聊天ListView使用ViewHolder

聊天界面會展示至少兩種布局，即收到消息和發(fā)送消息。這樣一個ListView與平時使用的ListView的最大不同，在于它有兩個不同的布局：收到的布局和發(fā)送的布局。需要利用Adapter實現(xiàn)這樣的效果。即需要在獲取布局的時候判斷該獲取哪個布局。

public abstract class BaseAdapter extends Object
implements ListAdapter SpinnerAdapter java.lang.Object ???? android.widget.BaseAdapter

BaseAdapter這個類中提供了兩個方法：

public intgetItemViewType (int position) Added in API level 1

Get the type of View that will be created by getView(int, View, ViewGroup) for the specified item.

ParametersThe position of the item within the adapter's data set whose view type we want. Returns? 返回第position個Item是何種類型 An integer representing the type of View. Two views should share the same type if one can be converted to the other ingetView(int, View, ViewGroup). Note: Integers must be in the range 0 togetViewTypeCount() - 1. IGNORE_ITEM_VIEW_TYPE can also be returned.

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public intgetViewTypeCount () Added in API level 1

Returns the number of types of Views that will be created by getView(int, View, ViewGroup). Each type represents a set of views that can be converted ingetView(int, View, ViewGroup). If the adapter always returns the same type of View for all items, this method should return 1.

This method will only be called when when the adapter is set on the the AdapterView.

Returns 返回不同布局的數(shù)目 The number of types of Views that will be created by this adapter

首先需要實現(xiàn)兩個布局——發(fā)送和接收

chat_item_itemin.xml

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chat_item_itemout.xml

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為了封裝聊天內容，便于在Adapter中獲取數(shù)據(jù)信息，封裝一個Bean類來保存聊天信息。編寫javabean就是編寫一個java的類，所以只要會寫類就能編寫一個bean，這個類創(chuàng)建的一個對象稱做一個bean。為了能讓使用這個bean的應用程序構建工具（比如JSP引擎）知道這個bean的屬性和方法，只需在類的方法命名上遵守以下規(guī)則：

1． 如果類的成員變量的名字是xxx，那么為了更改或獲取成員變量的值，即更改或獲取屬性，在類中可以使用兩個方法：

getXxx()，用來獲取屬性xxx。

setXxx()，用來修改屬性xxx。

2． 對于boolean類型的成員變量，即布爾邏輯類型的屬性，允許使用"is"代替上面的"get"和"set"。

3． 類中方法的訪問屬性都必須是public的。

4． 類中如果有構造方法，那么這個構造方法也是public的并且是無參數(shù)的。

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ChatItemListViewBean.java

package?sunny.example.ahfourlistviewchat;

//封裝一個Bean來保存聊天信息
import?android.graphics.Bitmap;
public?class?ChatItemListViewBean?{

	private?int?type;
	private?String?text;
	private?Bitmap?icon;
	
	public?ChatItemListViewBean(){
		
	}
	
	public?int?getType(){
		return?type;
	}
	//在使用時setType?如bean1.setType(0);
	public?void?setType(int?type){
		this.type?=?type;
	}
	
	public?String?getText(){
		return?text;
	}
	
	public?void?setText(String?text){
		this.text?=?text;
	}
	
	public?Bitmap?getIcon(){
		return?icon;
	}
	
	public?void?setIcon(Bitmap?icon){
		this.icon?=?icon;
	}
}

activity_main.xml

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ChatItemListViewTest.java

package?sunny.example.ahfourlistviewchat;

import?android.support.v7.app.ActionBarActivity;
import?android.widget.ListView;
import?android.graphics.BitmapFactory;
import?android.os.Bundle;
import?java.util.List;
import?java.util.ArrayList;
public?class?ChatItemListViewTest?extends?ActionBarActivity{

	private?ListView?mListView;
	protected?void?onCreate(Bundle?savedInstanceState){
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		mListView?=?(ListView)findViewById(R.id.listView_chat);
		ChatItemListViewBean?bean1?=?new?ChatItemListViewBean();
		bean1.setType(0);
		bean1.setIcon(BitmapFactory.decodeResource(getResources(),?R.drawable.ic_launcher));
		bean1.setText("Hello.?How?are?you?");
		
		ChatItemListViewBean?bean2?=?new?ChatItemListViewBean();
		bean2.setType(1);
		bean2.setIcon(BitmapFactory.decodeResource(getResources(),?R.drawable.ic_launcher));
		bean2.setText("Fine.?Thank?you");
		
		Listdata?=?new?ArrayList();
		data.add(bean1);
		data.add(bean2);
		mListView.setAdapter(new?ChatItemListViewAdapter(this,data));
	}
}

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