优化使用的BaseAdapter

ListView在使用自定的BaseAdapter时，为了加载快速，用到了封装item的方法和ViewHolder的方法。代码如下：

首先想要在显示一个ListView，在activity_mian.xml中加入一个ListView：

<RelativeLayout 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:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.chase.baseadapterwell.MainActivity" >

<ListView
android:id="@+id/listview"
android:layout_width="match_parent"
android:layout_height="match_parent"
></ListView>

</RelativeLayout>

ListView的每个Item的布局item.xml：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="vertical" >

<ImageView
android:id="@+id/iv_image"
android:layout_width="60dp"
android:layout_height="60dp"
android:src="@drawable/ic_launcher" />

<TextView
android:id="@+id/tv_title"
android:layout_width="match_parent"
android:layout_height="30dp"
android:gravity="center"
android:layout_toEndOf="@+id/iv_image"
android:text="Title"
android:textSize="25sp" />

<TextView
android:id="@+id/tv_content"
android:layout_width="match_parent"
android:layout_height="30dp"
android:layout_toEndOf="@+id/iv_image"
android:layout_below="@+id/tv_title"
android:gravity="center_vertical"
android:text="Content"
android:textSize="25sp" />

</RelativeLayout>

将上面的布局封装为ItemBean，新建一个类ItemBean

package com.chase.baseadapterwell;

public class ItemBean {

public int ItemImageResid;
public String ItemTitle;
public String ItemContent;

//形成构造方法在eclipse中是Source-Generate Constructor using Fields...
public ItemBean(int itemImageResid, String itemTitle, String itemContent) {
super();
ItemImageResid = itemImageResid;
ItemTitle = itemTitle;
ItemContent = itemContent;
}

}

新建MyAdapter类继承BaseAdapter

package com.chase.baseadapterwell;

import java.util.List;

import android.content.Context;
import android.provider.Telephony.Sms.Conversations;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;

public class MyAdapter extends BaseAdapter {

private List<ItemBean> mList; // 创建一个成员变量用来保存传进来的数据
private LayoutInflater mInflater; // 要将布局转为view 用到inflater

public MyAdapter(Context context, List<ItemBean> list) {
mList = list; // 创建的成员变量=传进来的
// 所以在数据适配器中，只需要对mlist进行操作就可以了
mInflater = LayoutInflater.from(context); // 用context对minflater初始化
}

// 返回ListView需要的数据数量
@Override
public int getCount() {
// TODO Auto-generated method stub
return mList.size();
}

// 指定索引对于数据项
@Override
public Object getItem(int position) {
// TODO Auto-generated method stub
return mList.get(position);
}

// 返回对应索引
@Override
public long getItemId(int position) {
// TODO Auto-generated method stub
return position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
// TODO Auto-generated method stub
ViewHolder viewHolder;
if (convertView == null) {
convertView = mInflater.inflate(R.layout.item, null); // 将xml文件转为view

viewHolder = new ViewHolder();
// 用viewHolder来保存findviewByid找到的对象
viewHolder.imageView = (ImageView) convertView
.findViewById(R.id.iv_image);
viewHolder.title = (TextView) convertView
.findViewById(R.id.tv_title);
viewHolder.content = (TextView) convertView
.findViewById(R.id.tv_content);
convertView.setTag(viewHolder); // 将viewHolder与convertView绑定
} else {
viewHolder = (ViewHolder) convertView.getTag();// getTag取出关联的ViewHolder
// 通过ViewHolder找到对应控件
}

ItemBean bean = mList.get(position);
viewHolder.imageView.setImageResource(bean.ItemImageResid);
viewHolder.title.setText(bean.ItemTitle);
viewHolder.content.setText(bean.ItemContent);
return convertView;
}

// 创建内部类ViewHolder 对应布局中的控件
class ViewHolder {
public ImageView imageView;
public TextView title;
public TextView content;
}
}

MainActivity中 做一个演示用的数据源 并且listview设定适配器`

package com.chase.baseadapterwell;

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

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

//制造一个演示用的数据源
List<ItemBean>itemBeanList = new ArrayList<ItemBean>();
for (int i = 0; i < 20; i++) {
itemBeanList.add(new ItemBean(R.drawable.ic_launcher,
"我是标题"+i, "我是内容"+i));
}

ListView listView = (ListView) findViewById(R.id.listview);
listView.setAdapter(new MyAdapter(this, itemBeanList)); //(上下文，数据源)

}
}