Android入门：ListView(继承BaseAdapter实现)

任务：

从数据库中获得Person对象，通过继承BaseAdapter类，显示ListView，如下所示：

（此处我们数据库操作的代码略，因为主要讲解的是ListView）

PersonAdapter.java

package org.xiazdong.db.domain;

import java.util.List;

import org.xiazdong.db.R;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;

public class PersonAdapter extends BaseAdapter {

	private List<Person> persons;	//数据
	private int resource;	//item的布局
	private Context context;
	private LayoutInflater inflator;
	private TextView nameTextView;
	private TextView ageTextView;
	private TextView idTextView;
	/**
	 * 
	 * @param context mainActivity
	 * @param persons	显示的数据
	 * @param resource 	一个Item的布局
	 */
	public PersonAdapter(Context context,List<Person>persons,int resource){
		this.context = context;
		this.persons = persons;
		this.resource = resource;
	}
	/*
	 * 获得数据总数
	 * */
	@Override
	public int getCount() {
		return persons.size();
	}
	/*
	 * 根据索引为position的数据
	 * */
	@Override
	public Object getItem(int position) {
		return persons.get(position);
	}
	/*
	 * 根据索引值获得Item的Id
	 * */
	@Override
	public long getItemId(int position) {
		return position;
	}
	/*
	 *通过索引值position将数据映射到视图
	 *convertView具有缓存功能，在第一页时为null，在第二第三....页时不为null
	 * */
	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		if(convertView==null){
			inflator = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
			convertView = inflator.inflate(resource, null);
			nameTextView = (TextView)convertView.findViewById(R.id.name);	//为了减少开销，则只在第一页时调用findViewById
			ageTextView =(TextView) convertView.findViewById(R.id.age);
			idTextView = (TextView)convertView.findViewById(R.id.id1);
		}
		Person person = persons.get(position);
		nameTextView.setText(person.getName());
		idTextView.setText(person.getId()+"");
		ageTextView.setText(person.getAge()+"");
		return convertView;
	}
}

MainActivity.java

package org.xiazdong.db;

import java.util.List;

import org.xiazdong.db.domain.Person;
import org.xiazdong.db.domain.PersonAdapter;
import org.xiazdong.db.service.DBService;

import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;

public class MainActivity extends Activity {
	private ListView listView;
	@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        listView = (ListView)this.findViewById(R.id.listview);
        DBService service = new DBService(this);
        List<Person> persons = service.pageQuery(0, 10);
        PersonAdapter adapter = new PersonAdapter(this,persons, R.layout.item);
        listView.setAdapter(adapter);
	}
}