使用BaseAdapter实现ListView

             

                 Adapter为一个接口，其实现类中 ArraryAdapter、SimpleAdapter、SimpleCursorAdapter、BaseAdapter比较使我们比较常用的几个实现类。

                通过BaseAdapter实现Adapter，使用BaseAdapter 的好处在于我们可以自己决定创建多少个列表项和每个列表项的组件。如下简单的例子来演示BaseAdapter的用法。初学勿怪

自定义一个item

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="match_parent"
    android:orientation="vertical" >
    
    <ImageView 
        android:id="@+id/imageview"
        android:layout_width="65dp"
        android:layout_height="65dp"
        android:src="@drawable/normal"/>
    
    <TextView 
        android:id="@+id/tvname"
        android:layout_width="match_parent"
        android:layout_height="40dp"
        android:layout_marginLeft="70dp"
        android:textSize="18sp"
        android:gravity="center_vertical"/>
      
    <TextView 
        android:id="@+id/tvmessage"
        android:layout_width="fill_parent"
        android:layout_height="25dp"
        android:layout_marginLeft="70dp"
        android:layout_below="@+id/tvname"
        android:textSize="15sp"
        android:gravity="center_vertical"/>

</RelativeLayout>

Listbean.java 

package com.example.text;

public class listbean {
	
	private int imageid;
	private String name;
	private String message;
	
	public listbean(int imageid, String name, String message) {
		super();
		this.imageid = imageid;
		this.name = name;
		this.message = message;
	}
    public int getimageid(){
		return imageid;
	}
	
	public void setimageid(int imageid) {
	    this.imageid=imageid;	
	}
	

	public String getname(){
		return name;
	}
	
	public void setname(String name) {
	    this.name=name;	
	}
	
    public String getmessage(){
		return message;
	}
	
	public void setimageid(String message) {
	    this.message=message;	
	}
	
	}

MainActivity.java

package com.example.text;

import java.util.ArrayList;
import java.util.List;
import com.example.text.R;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;


public class MainActivity extends Activity {
    private ListView listView;
    List<listbean> listnm = new ArrayList<listbean>();

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		listView=(ListView) findViewById(R.id.listviev);
        for (int i = 0; i < 50; i++) {

                     //可以自定义一个Listbean;

                     //调用它的构造函数public listbean(int imageid, String name, String message)
                  listnm.add(new <span style="color:#330099;">listbean</span>(R.drawable.normal, "列表项"+i, "初识baseadapter"+i));
		}
        
      listView.setAdapter(new Listadapter(MainActivity.this, listnm));
	}

}

Listadapter.java

package com.example.text;

import java.util.ArrayList;
import java.util.List;
import com.example.text.R;
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 Listadapter extends BaseAdapter {
	List<listbean> listnm = new ArrayList<listbean>();
	private LayoutInflater linflater;
	
	public Listadapter(Context context,List<listbean> listtm){
		this.listnm=listtm;
		linflater = LayoutInflater.from(context);
	}

	@Override
	public int getCount() {
		return listnm.size();
	}

	@Override
	public Object getItem(int position) {
		return listnm.get(position);
	}

	@Override
	public long getItemId(int position) {
		return position;
	}

	@Override
	public View getView(int position, View view, ViewGroup parent) {
		ViewHolder viewHolder = new ViewHolder();
		if(view==null){
			view = linflater.inflate(R.layout.item, null);
			viewHolder.imageView=(ImageView) view.findViewById(R.id.imageview);
			viewHolder.tvname=(TextView) view.findViewById(R.id.tvname);
			viewHolder.tvmessage=(TextView) view.findViewById(R.id.tvmessage);
			view.setTag(viewHolder);
		}else {
			viewHolder = (ViewHolder) view.getTag();
		}
		listbean listbean = listnm.get(position);
		viewHolder.imageView.setImageResource(listbean.getimageid());
		viewHolder.tvname.setText(listbean.getname());
		viewHolder.tvmessage.setText(listbean.getmessage());
		return view;
	}
	 
	  public final class ViewHolder{
		  public ImageView imageView;
		  public TextView tvname;
		  public TextView tvmessage;
		  
	  }
}

运行项目：

如上例子 创建了一个BaseAdapter 对象，主要有4个方法：

1、getCount():返回该adapter包含多少个列表项。

2、getItem(int position): 返回处于第几项的列表项的值。

3、getItemId(int position):返回处于第几项的列表的ID。

4、getView(int position, View view, ViewGroup parent) ：返回第几处的列表项的组件。