数据适配器 BaseAdapter

BaseAdapter 基本结构

------public int getCount():适配器中数据集中数据的个数

-----public Object getItem(int position):获取数据集中与指定索引对应的数据项

-----public long getItemId(int position):获取指定行对应的ID

-----public View getView(int position,View convertView,ViewGroup parent):获取每一个Item 的显示内容

下面通过Listview 和BaseAdpter 实现下面功能

首先制作布局文件item.xml

<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"    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=".MainActivity" >    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content" >        <ImageView            android:id="@+id/iv_image"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:src="@drawable/ic_launcher" />        <LinearLayout            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:orientation="vertical" >            <TextView                android:id="@+id/tv_title"                android:layout_width="match_parent"                android:layout_height="30dp"                android:layout_toEndOf="@+id/iv_image"                android:gravity="center"                android:text="title"                android:textSize="25sp" />            <TextView                android:id="@+id/tv_content"                android:layout_width="match_parent"                android:layout_height="30dp"                android:layout_below="@+id/tv_title"                android:layout_toEndOf="@+id/iv_image"                android:gravity="center_vertical"                android:text="content"                android:textSize="20sp" />        </LinearLayout>    </LinearLayout></LinearLayout>

效果图如下

下面用ItemBean.java 类来封装 布局文件

public class ItemBean {int ItemImageResid;String ItemTitle;String ItemContent;public ItemBean(int ItemImageResid, String ItemTitle, String ItemContent) {this.ItemImageResid = ItemImageResid;this.ItemTitle = ItemTitle;this.ItemContent = ItemContent;}}

下面用myBaseAdapter.java类

import java.util.List;import android.content.Context;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 myBaseAdpter extends BaseAdapter {private List<ItemBean> mList;private LayoutInflater minflater;public myBaseAdpter(Context context, List<ItemBean> list) {mList = list;this.minflater = LayoutInflater.from(context);// context要使用当前的Adapter的界面对象mInflater布局装载器对象}@Overridepublic int getCount() {// TODO Auto-generated method stubreturn mList.size();// 返回ListView 所要显示的数据个数}@Overridepublic Object getItem(int arg0) {// TODO Auto-generated method stubreturn mList.get(arg0);}@Overridepublic long getItemId(int arg0) {// TODO Auto-generated method stubreturn arg0; // 返回指定索引对应的数据项}@Override// 返回每一项的显示内容public View getView(int arg0, View arg1, ViewGroup arg2) {// 逗比式//// View view=minflater.inflate(R.layout.item,null);//R.layout.item// 是需要装载到item中的布局文件// ImageView imageView=(ImageView)view.findViewById(R.id.iv_image);// TextView title=(TextView)view.findViewById(R.id.tv_title);// TextView content=(TextView)view.findViewById(R.id.tv_content);// ItemBean bean=mList.get(arg0);// imageView.setImageResource(bean.ItemImageResid);// title.setText(bean.ItemTitle);// content.setText(bean.ItemContent);// return view;// 普通式 利用了listview 的缓存机制 如果没有缓存 才创建新的view// 但是 大量findViewById 依然会浪费时间// if(arg1==null){// arg1=minflater.inflate(R.layout.item,null);// }// ImageView imageView=(ImageView)arg1.findViewById(R.id.iv_image);// TextView title=(TextView)arg1.findViewById(R.id.tv_title);// TextView content=(TextView)arg1.findViewById(R.id.tv_content);// ItemBean bean=mList.get(arg0);// imageView.setImageResource(bean.ItemImageResid);// title.setText(bean.ItemTitle);// content.setText(bean.ItemContent);// return arg1;// 文艺式 利用了listview 的缓存 更痛ViewHolder类实现显示数据的视图缓存 避免多次findViewById 寻找控件ViewHolder viewHolder;if (arg1 == null) {viewHolder = new ViewHolder();arg1 = minflater.inflate(R.layout.item, null);viewHolder.imageView = (ImageView) arg1.findViewById(R.id.iv_image);viewHolder.title = (TextView) arg1.findViewById(R.id.tv_title);viewHolder.content = (TextView) arg1.findViewById(R.id.tv_content);arg1.setTag(viewHolder);} else {viewHolder = (ViewHolder) arg1.getTag();}ItemBean bean = mList.get(arg0);viewHolder.imageView.setImageResource(bean.ItemImageResid);viewHolder.title.setText(bean.ItemTitle);viewHolder.content.setText(bean.ItemContent);return arg1;}class ViewHolder {public ImageView imageView;public TextView title;public TextView content;}}

最后 是MainActivity.java

import java.util.ArrayList;import java.util.List;import android.os.Bundle;import android.app.Activity;import android.view.Menu;import android.widget.ListView;public class MainActivity extends Activity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        List<ItemBean> itemBeanList=new ArrayList<ItemBean>();        for(int i=0;i<20;i++){        itemBeanList.add(new ItemBean(R.drawable.ic_launcher, "标题"+i, "内容"+i));        }        ListView listView=(ListView)findViewById(R.id.lv_main);        listView.setAdapter(new myBaseAdpter(this,itemBeanList));    }    @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;    }    }

main_activity.xml

<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=".MainActivity" >    <ListView        android:id="@+id/lv_main"        android:layout_width="match_parent"        android:layout_height="match_parent"         /></RelativeLayout>