BaseAdapter优化使用

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MainActivity

package com.example.administrator.baseadapter;import android.app.Activity;import android.os.Bundle;import android.widget.ListView;import java.util.ArrayList;import java.util.List;public class MainActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        List<ItemBean> itemBeanList = new ArrayList<>();        for (int i = 0; i < 20;i++){            itemBeanList.add(new ItemBean(R.mipmap.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));    }}

class ItemBean

//此类用来封装对象public class ItemBean {    public int ItemImage;    public String ItemTitlel;    public String ItemContent;    public ItemBean(int itemImage, String itemTitlel, String itemContent) {        ItemImage = itemImage;        ItemTitlel = itemTitlel;        ItemContent = itemContent;    }}

class Myadapter

public class MyAdapter extends BaseAdapter {    private LayoutInflater mInflater;    private List<ItemBean>mList;//创建一个成员变量用来保存传递进来的数据    public MyAdapter(Context context,List<ItemBean>list){       //数据源与适配器关联，为了从数据源中获取要传进来的数据，                                                                // 通常在BaseAdapter的构造方法中对数据进行初始化        mList = list;        mInflater = LayoutInflater.from(context); //context 要使用当前的Adapter的界面对象mInflater布局装载对象，                                                 // 传递进一个Context对象来初始化Inflater对象    }    @Override    public int getCount() {        return mList.size();    }    @Override    public Object getItem(int position) {        return mList.get(position);    }    @Override    public long getItemId(int position) {        return position;    }    @Override    public View getView(int position, View convertView, ViewGroup parent) { //返回每一项的显示内容        ViewHolder viewHolder;        if (convertView == null){            viewHolder = new ViewHolder();            convertView = mInflater.inflate(R.layout.item,null);            viewHolder.image= (ImageView) convertView.findViewById(R.id.image);            viewHolder.title = (TextView) convertView.findViewById(R.id.title);//通过viewHolder的对象将findViewById找到的对象保存起来            viewHolder.content = (TextView) convertView.findViewById(R.id.content);            convertView.setTag(viewHolder);//建立convertView与viewHolder的关联关系        }        else{            viewHolder = (ViewHolder) convertView.getTag();        }        ItemBean bean = mList.get(position);        viewHolder.image.setImageResource(bean.ItemImage);        viewHolder.title.setText(bean.ItemTitlel);        viewHolder.content.setText(bean.ItemContent);        return convertView;        /*不仅利用了ListView的缓存机制，更用过ViewHolder类来实现显示数据的视图缓存，        避免多次通过findViewById来寻找控件。         */    }    class  ViewHolder {  //创建内部类ViewHolder        public ImageView image;        public TextView title;          //避免重复的findViewById操作        public TextView content;    }}

下面是布局文件

activity_main

<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.example.administrator.baseadapter.MainActivity">    <ListView        android:layout_width="match_parent"        android:layout_height="match_parent"        android:id="@+id/listview"></ListView></RelativeLayout>

Item.xml

<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:layout_width="60dp"        android:layout_height="60dp"        android:id="@+id/image"        android:src="@mipmap/ic_launcher"/>    <TextView        android:layout_width="match_parent"        android:layout_height="30dp"        android:layout_toRightOf="@+id/image"        android:text="Title"        android:gravity="center"        android:textSize="20sp"        android:id="@+id/title"/>    <TextView        android:layout_width="match_parent"        android:layout_height="30dp"        android:layout_toRightOf="@+id/image"        android:layout_below="@+id/title"        android:text="Content"        android:textSize="20sp"        android:id="@+id/content"/></RelativeLayout>

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