优化使用的BaseAdapter

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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)    }}

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