ArrayAdapter做的listview适配器

//安卓开发：ArrayAdapter做的listview适配器
public class PersonAdapter extends ArrayAdapter {
private LayoutInflater layoutInflater = null;
    private List<Person> persons;


    public PersonAdapter(Context context, int textViewResourceId, List objects) {
        super(context, textViewResourceId, objects);
        layoutInflater = LayoutInflater.from(context);
        persons = objects;
    }
    
    
    @Override
    public int getCount() {
        return persons.size();
    }


    @Override
    public Object getItem(int position) {
        return persons.get(position);
    }
    
    @Override
    public long getItemId(int position) {
        return position;
    } 
    
    
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        /*
        // 优化前
        ViewHolder holder = new ViewHolder();
        convertView = layoutInflater.inflate(R.layout.main, null);
        holder.id = (TextView)convertView.findViewById(R.id.id);
        holder.name = (TextView)convertView.findViewById(R.id.name);
        holder.age = (TextView)convertView.findViewById(R.id.age);
        convertView.setTag(holder);
        
        holder.id.setText(persons.get(position).getId());
        holder.name.setText(persons.get(position).getName());
        holder.age.setText(persons.get(position).getAge());
        return convertView;
        */
        
        // 优化后
        ViewHolder holder;
        if(convertView == null){
            convertView = layoutInflater.inflate(R.layout.activity_main, null);
            holder = new ViewHolder();
            holder.id = (TextView)convertView.findViewById(R.id.id);
            holder.name = (TextView)convertView.findViewById(R.id.name);
            holder.age = (TextView)convertView.findViewById(R.id.age);
            convertView.setTag(holder);
        }else{
            holder = (ViewHolder)convertView.getTag();
        }
        
        holder.id.setText(persons.get(position).getId());
        holder.name.setText(persons.get(position).getName());
        holder.age.setText(persons.get(position).getAge());
        return convertView;
    }
    
    private static class ViewHolder{
        private TextView id;
        private TextView name;
        private TextView age;
    }

}

package com.example.alistviewexample;
public class Person {
private String id;
   private String name;
   private String age;
public Person(String id, String name, String age) {
super();
this.id = id;
this.name = name;
this.age = age;
}
   
public Person(){}


public String getId() {
return id;
}


public void setId(String id) {
this.id = id;
}


public String getName() {
return name;
}


public void setName(String name) {
this.name = name;
}


public String getAge() {
return age;
}


public void setAge(String age) {
this.age = age;
}
}

package com.example.alistviewexample;
import java.util.ArrayList;
import android.os.Bundle;
import android.app.Activity;
import android.app.ListActivity;
import android.view.Menu;
import android.view.View;
import android.widget.ListView;
import android.widget.Toast;
public class MainActivity extends ListActivity {

private ArrayList<Person> persons = new ArrayList<Person>();
   private PersonAdapter personAdapter = null;


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

initData();
       personAdapter =new PersonAdapter(MainActivity.this, R.layout.activity_main, persons);
       setListAdapter(personAdapter);
       registerForContextMenu(getListView());

}


@Override
   protected void onListItemClick(ListView l, View v, int position, long id) {
       super.onListItemClick(l, v, position, id);
       Person person = persons.get(position);
       Toast.makeText(MainActivity.this, person.getId()+":"+person.getName()
               +":"+person.getAge(), Toast.LENGTH_LONG).show();
       return;
   }
 
private void initData(){
       persons.add(new Person("序号", "姓名", "年龄"));
       persons.add(new Person("1", "ljq1", "20"));
       persons.add(new Person("2", "ljq2", "20"));
       persons.add(new Person("3", "ljq3", "20"));
       persons.add(new Person("4", "ljq4", "20"));
       persons.add(new Person("5", "ljq5", "20"));
       persons.add(new Person("6", "ljq6", "20"));
       persons.add(new Person("7", "ljq7", "20"));
       persons.add(new Person("8", "ljq8", "20"));
       persons.add(new Person("9", "ljq9", "20"));
   }
}

<?xml version="1.0" encoding="utf-8"?>
<!-- 使用相对布局 -->
<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" 
    android:layout_width="wrap_content"
    android:layout_height="wrap_content">
    <TextView android:layout_width="100dip"
        android:layout_height="wrap_content"
        android:layout_marginLeft="30dip"
        android:textSize="20dip"
        android:id="@+id/id"/>
    <TextView android:layout_width="100dip"
        android:layout_height="wrap_content"
        android:layout_alignTop="@id/id"
        android:layout_toRightOf="@id/id"
        android:textSize="20dip"
        android:id="@+id/name"/>
    <TextView android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@id/name"
        android:layout_toRightOf="@id/name"
        android:textSize="20dip"
        android:id="@+id/age"/>
</RelativeLayout>