填充ListView(继承BaseAdapter)

package com.example.test;

import android.app.Activity;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ListView;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class ListData extends Activity {
private List<Person> personList;

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

MyDBHelper helper = new MyDBHelper(this);
SQLiteDatabase db = helper.getWritableDatabase();
Cursor cursor = db.rawQuery("select name,age from person", null);
personList = new ArrayList<Person>();
while (cursor.moveToNext()) {
String name = cursor.getString(0);
String age = cursor.getString(1);
Person person = new Person(name, age);
personList.add(person);
}

ListView list = (ListView) findViewById(R.id.list);
list.setAdapter(new MyAdapter());
}

class MyAdapter extends BaseAdapter {

//这个可以不实现
@Override
public Object getItem(int position) {
return null;
}

//这个可以不实现
@Override
public long getItemId(int position) {
return 0;
}

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

@Override
public View getView(int position, View convertView, ViewGroup parent) {
System.out.println(position);

/**
*    View v=null;
*    if(convertView==null){
*      TextView textView=new TextView(ListData.this);
*      textView.setText(personList.get(position).toString());
*      textView.setTextSize(18);
*      v=textView;
*    }else{
*          v=convertView;
*    }
* 这样编写是不对的
* 因为当这个listview滑动的时候会缓存很多个textView，而当listview要获取他的缓存时
* 不能确定要获取哪一个缓存，只能是随机获取一个
* 所以正确的应该是
*
*
*/
TextView textView = new TextView(ListData.this);
textView.setText(personList.get(position).toString());
textView.setTextSize(18);
return textView;

}
}

}

package com.example.test;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;

/**
* Created by joy on 2015/12/26.
*/
public class MyDBHelper extends SQLiteOpenHelper {
private final static String DB_NAME="person.db";
public MyDBHelper(Context context) {
//第一个参数上下文，第二个参数数据库名，第三个参数游标工厂，第四个参数数据库版本号
//数据库文件保存在data/data/包名/databases/person.db
super(context, DB_NAME, null, 2);
}

@Override
public void onCreate(SQLiteDatabase db) {
//数据库创建时调用
db.execSQL("create table person(_id integer primary key autoincrement,name varchar(20),age varchar(2))");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
//数据库升级时调用
Log.e("gjj","数据库更新了");
}
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
>

<ListView
android:id="@+id/list"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />

</LinearLayout>

package com.example.test;

/**
* Created by joy on 2015/12/24.
*/
public class Person {
private String name;
private String age;

public String getName() {
return name;
}

public String getAge() {
return age;
}

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

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

public Person(String name, String age) {
this.name = name;
this.age = age;
}

@Override
public String toString() {
return name +
", " + age;
}
}