3.安卓基础之数据库&listview&对话框

1. Android的xml的解析器

1.1 XML解析案例

• 解析手机号码吉凶案例

MainActivity.java

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

        //使用xml pull 解析器去解析xml文件的内容
        XmlPullParser parser = Xml.newPullParser();

        try {
			InputStream in = getAssets().open("result.xml");
			parser.setInput(in, "gbk");

			//获取事件的类型
			int eventType = parser.getEventType();

			/*
			<?xml version="1.0" encoding="gbk"?>
			<smartresult>
			  <product type="mobile">
				<phonenum>13512345678</phonenum>
				<location>重庆移动神州行卡</location>
				<phoneJx>有得有失，华而不实，须防劫财，始保平安 吉带凶</phoneJx>
			 </product>
			</smartresult>
			 * 			
			 */
			Product p = null;
			while(eventType!=XmlPullParser.END_DOCUMENT){
				//判断是否是元素的开始,只要是某个元素的开始位置,那么就会进入
				//获得当前元素解析的元素的名称
				if("product".equals(parser.getName())){
					p = new Product();
					String type = parser.getAttributeValue(0);//product
					p.setType(type);
				}else if("phonenum".equals(parser.getName())){
					String phonenum = parser.nextText();
					p.setPhonenum(phonenum);
				}else if("location".equals(parser.getName())){
					String location = parser.nextText();
					p.setLocation(location);
				}else if("phoneJx".equals(parser.getName())){
					String phoneJx = parser.nextText();
					p.setPhoneJx(phoneJx);
				}
				//手动挪动指针
				eventType = parser.next();
			}
			if(p!=null){
				Log.d("ProductMessange",p.toString());
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
    }

result.xml

<?xml version="1.0" encoding="gbk"?>
<smartresult>
 <product type="mobile">
	<phonenum>13512345678</phonenum>
	<location>重庆移动神州行卡</location>
	<phoneJx>有得有失，华而不实，须防劫财，始保平安 吉带凶
	</phoneJx>
 </product>
</smartresult>

Product.java

package com.example.xmlpullparsertest;
/*
 *
 *   封装数据的 标 准的 javabean
 *
<product type="mobile">
	<phonenum>13512345678</phonenum>
	<location>重庆移动神州行卡</location>
	<phoneJx>有得有失，华而不实，须防劫财，始保平安 吉带凶</phoneJx>
 </product>
 *
 */
public class Product {
	private String type;
	private String phonenum;
	private String phoneJx;
	private String location;

	public String getLocation() {
		return location;
	}
	public void setLocation(String location) {
		this.location = location;
	}
	public String getType() {
		return type;
	}
	public void setType(String type) {
		this.type = type;
	}
	public String getPhonenum() {
		return phonenum;
	}
	public void setPhonenum(String phonenum) {
		this.phonenum = phonenum;
	}
	public String getPhoneJx() {
		return phoneJx;
	}
	public void setPhoneJx(String phoneJx) {
		this.phoneJx = phoneJx;
	}

	@Override
	public String toString() {
		return "Product [type=" + type + ", phonenum=" + phonenum
				+ ", phoneJx=" + phoneJx + "]";
	}

}

2. 保存数据到数据库中的作用

如果保存的数据是有规律的,格式是同样的.那么可以去选择使用数据库保存数据.Android提供的数据库(sqlite)数据库.

• android提供的数据库小应用

MainActivity.java

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

        MySqliteHelper helper = new MySqliteHelper(MainActivity.this);
        helper.getReadableDatabase();
    }

MySqliteHelper.java

package com.example.sqlitedemo;

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

public class MySqliteHelper extends SQLiteOpenHelper {
	public MySqliteHelper(Context context){
		//context:应用上下文
		//name:数据库的名词
		//factory:创建游标的工厂
		//version:数据库的版本
		super(context, "mydb1", null, 4);

		/*
		 mysql

		create table users(
		   id int primary key auto_increment,
		   name varchar(30)
		);

		android 中 :

		create table students(
		   id integer primary key autoincrement,
		   name varchar(30)
		);

		 */

	}

	//在数据库首次被创建时调用
	@Override
	public void onCreate(SQLiteDatabase db) {
		db.execSQL("create table students ( _id integer primary key autoincrement,name varchar(30), sex varchar(10))");

	}

	//在数据库升级时调用,当版本比之前的版本高时会执行该方法!
	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		db.execSQL("alter table students add number varchar(10)");

	}

}

• StudentSystem在SQLiteOpenHelper的应用详细版

Student.java

package domain;

public class Student {

	private String id;
	private String name;
	private String sex;

	public Student(){

	}
	public Student(String id,String name,String sex){
		this.name = name;
	 	this.id = id;
		this.sex = sex;
	}
	public String getId() {
		return id;
	}
	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + ", sex=" + sex + "]";
	}
	public void setId(String id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
}

StudentDao.java

package com.example.studentsystemdemo1;

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

import domain.Student;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class StudentDao {
	StudentDbOpenHelper helper;
	public StudentDao(Context context){
		helper = new StudentDbOpenHelper(context);
	}

	public void add(Student st){
		//拿到工具类的实例,然后去操作数据库
		SQLiteDatabase db = helper.getReadableDatabase();

		//执行sql语句
		db.execSQL("insert into students values(null,?,?)",new Object[]{st.getName(),st.getSex()});
	}

	public void delete(String id){
		SQLiteDatabase db = helper.getReadableDatabase();
		db.execSQL("delete from students where _id=?",new Object[]{id});
	}

	public void update(Student st){
		SQLiteDatabase db = helper.getReadableDatabase();
		db.execSQL("update students set name=?,sex=? where _id=?", new Object[]{st.getName(),st.getSex(),st.getId()});
	}

	public Student find(String id){
		SQLiteDatabase db = helper.getReadableDatabase();
		Cursor cursor = db.rawQuery("select * from students where _id=?", new String[]{id});

		boolean result = cursor.moveToNext();

		Student st = null;
		if(result){
			int _id = cursor.getInt(cursor.getColumnIndex("_id"));
			String name = cursor.getString(cursor.getColumnIndex("name"));
			String sex = cursor.getString(cursor.getColumnIndex("sex"));

			st = new Student(String.valueOf(id),name,sex);

		}
		cursor.close();
		return st;
	}

	//查询返回所有学生的信息
	public List<Student> getAll(){
		List<Student> list = new ArrayList<Student>();
		SQLiteDatabase db = helper.getReadableDatabase();

		Cursor cursor = db.rawQuery("select * from students", null);
		while(cursor.moveToNext()){
			int id = cursor.getInt(cursor.getColumnIndex("_id"));
			String name = cursor.getString(cursor.getColumnIndex("name"));
			String sex = cursor.getString(cursor.getColumnIndex("sex"));
			Student st = new Student(String.valueOf(id),name,sex);
			list.add(st);
		}
		list = null;
		return list;

	}

}

StudentDbOpenHelper.java

package com.example.studentsystemdemo1;

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

public class StudentDbOpenHelper extends SQLiteOpenHelper {

	public StudentDbOpenHelper(Context context){
		super(context, "student.db", null, 1);
	}
	@Override
	public void onCreate(SQLiteDatabase db) {
		//创建数据库
		db.execSQL("create table students (_id integer primary key autoincrement, name varchar(30),sex varchar(10))");

	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

	}

}

• 学生查询系统带item的应用:

Activity_main.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"
    tools:context=".MainActivity" >

    <EditText
        android:id="@+id/ed_name"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="请输入学生的姓名" />

    <RadioGroup
        android:id="@+id/rgb"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <RadioButton
            android:id="@+id/male"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:checked="true"
            android:text="男" />

        <RadioButton
            android:id="@+id/female"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="女" />
    </RadioGroup>

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="save"
        android:text="保存" />

    <ScrollView
        android:layout_width="fill_parent"
        android:layout_height="wrap_content" >

        <LinearLayout
            android:id="@+id/ll"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >
        </LinearLayout>
    </ScrollView>

</LinearLayout>

MainActivity.java

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

		//初始化
		ed_name = (EditText) findViewById(R.id.ed_name);
		rgb= (RadioGroup) findViewById(R.id.rgb);
		lv = (ListView) findViewById(R.id.lv);

		sdao = new StudentDao(this);

		refreshView();
	}

	public void save(View v){

		String name = ed_name.getText().toString().trim();

		if(TextUtils.isEmpty(name)){
			Toast.makeText(this, "学生信息不能为空", 0).show();
		return;
	}

	String sex ="male";

	int id = rgb.getCheckedRadioButtonId();
	if(id==R.id.male){
		sex ="male";
	}else{
		sex ="female";
	}

	//将数据 保存到数据库 中去

	// 拿到 dao

	Student st = new Student("xjlkj",name,sex);
	sdao.add(st);
	Toast.makeText(this, "保存  "+ name+"成功", 0).show();
	//将所有的数据同步的显示 到 屏幕上去

	//查询现有的数据
		refreshView();
	}

	List<Student> students;
	private MyAdapter myAdapter;
	private void refreshView() {

	// 将现有的全部给清空一下
	students = sdao.getAll();

	if(myAdapter ==null){
		myAdapter = new MyAdapter();
		//为 lv 设置数据适配器 --- 设置控制器controller
		lv.setAdapter(myAdapter);
	}else{

		//则说明myAdapter已经存在了,需要做的是,通知控制器 adapter去更新一下数据.
			myAdapter.notifyDataSetChanged();
		}

	}

	private class MyAdapter extends BaseAdapter{


	//最开始被调用的 , 用于告诉控制器 adapter到底要显示 多少个item
	@Override
	public int getCount() {

		//告诉控制器 adapter显示多少个item
		return students.size();
	}


	//每个item要显示在屏幕上时,又会调用到这个方法
	//convertView:就是用来进行优化的
	@Override
	public View getView(int position, View convertView, ViewGroup parent) {

	//获得当前的学生
	final Student st = students.get(position);

	//现在 item 已经定义好了,需要将硬盘上item.xml布局文件 转化为一个布局的对象返回去.

	View v;
	if (convertView == null) {
		v =  View.inflate(MainActivity.this, R.layout.item, null);
	} else {
		v = convertView;
	}


	//打气筒的对象 ,去填充xml,使得xml布局文件变为一个view对象.
	//拿到iv和tv

	ImageView iv = (ImageView) v.findViewById(R.id.item_iv);

	String sex = st.getSex();
	if("male".equals(sex)){
		iv.setImageResource(R.drawable.nan);
	}else{

		iv.setImageResource(R.drawable.nv);
	}


	TextView tv = (TextView) v.findViewById(R.id.item_tv);
	tv.setText(st.getName());


	v.findViewById(R.id.item_delete).setOnClickListener( new View.OnClickListener() {

		@Override
		public void onClick(View v) {

			/*System.out.println("=======  onClick 点击了 ");


			//需要拿到当前的点击的item ,将 学生的信息给删掉.
			//获得点击点击的item

			String id = st.getId();

			sdao.delete(id);
			Toast.makeText(MainActivity.this, "删除成功 : " + st.getName(), 0).show();

			//重新加载下数据
			refreshView();*/

			AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
			builder.setTitle("删除...");
			builder.setMessage("亲,你确定要删除吗? 不能反悔 的哦...");
			//设置点击确定的按钮
			builder.setPositiveButton("删除",new DialogInterface.OnClickListener() {

				@Override
				public void onClick(DialogInterface dialog, int which) {
					String id = st.getId();

					sdao.delete(id);
					Toast.makeText(MainActivity.this, "删除 成功 : " + st.getName(), 0).show();

					// 重新 加载 下 数据
					refreshView();
				}
			});

			//设置点击取消的的按钮
			builder.setNegativeButton("取消", null);

			//你需要 调用  相应的方法 才能够显示出来
		/*	AlertDialog dialog = builder.create();
			dialog.show();*/
				builder.show();
			}
		});

		return v;
	}

	@Override
	public Object getItem(int position) {
		// TODO Auto-generated method stub
		return null;
	}

	@Override
	public long getItemId(int position) {
		// TODO Auto-generated method stub
			return 0;
		}

	}

}

StudentDao.java

package com.example.studentsystemdemo2;

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

import domain.Student;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

public class StudentDao {
	StudentDbOpenHelper helper;

	public StudentDao(Context context){

		helper = new StudentDbOpenHelper(context);
	}

// "create table students (_id integer primary key autoincrement, name varchar(30),sex varchar(10))"
	public void add(Student st){

		//拿到工具类的实例, 然后去操作 数据库
		SQLiteDatabase db = helper.getWritableDatabase();

		//执行sql语句
		db.execSQL("insert into students values(null,?,?)",new Object[]{st.getName(),st.getSex()});

	}

	public void delete(String id){

		SQLiteDatabase db = helper.getWritableDatabase();
		db.execSQL("delete from students where _id=?",new Object[]{id});

	}
	public void update(Student st){

		SQLiteDatabase db = helper.getWritableDatabase();

		db.execSQL("update students set name=?,sex=? where _id=?", new Object[]{st.getName(),st.getSex(),st.getId()});
	}

	public Student find(String id){

		SQLiteDatabase db = helper.getReadableDatabase();

		//select * from users where id=?

		//叫做游标,与 javaweb中所学的resultSet结构是一样的  
		Cursor cursor = db.rawQuery("select * from students where _id=?", new String[]{id});

		boolean result = cursor.moveToNext();

		Student st = null;
		if(result){
//			st = new Student();
			/*int _id = cursor.getInt(0);
			String name = cursor.getString(1);
			String sex = cursor.getString(2);
			st.setId(id);
			st.setName(name);
			st.setSex(sex);*/

			int _id = cursor.getInt(cursor.getColumnIndex("_id"));
			String name = cursor.getString(cursor.getColumnIndex("name"));
			String sex =  cursor.getString(cursor.getColumnIndex("sex"));

			st = new Student(String.valueOf(_id),name,sex);

		}

		// 最后会释放 资源
		cursor.close();

		return st;
	}


	//查询返回所有的学生的信息
	public List<Student> getAll() {

		List<Student> list =new ArrayList<Student>();
		SQLiteDatabase db = helper.getReadableDatabase();

		Cursor cursor = db.rawQuery("select * from students", null);

		while(cursor.moveToNext()){

			int id = cursor.getInt(cursor.getColumnIndex("_id"));
			String name = cursor.getString(cursor.getColumnIndex("name"));
			String sex = cursor.getString(cursor.getColumnIndex("sex"));
			Student st = new Student(String.valueOf(id), name, sex);
			list.add(st);

		}


		return list;
	}
}

StudentDbOpenHelper.java

package com.example.studentsystemdemo2;

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

public class StudentDbOpenHelper extends SQLiteOpenHelper {

	public StudentDbOpenHelper(Context context) {
		super(context, "student.db", null, 1);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {

		//创建数据库
		db.execSQL("create table students (_id integer primary key autoincrement, name varchar(30),sex varchar(10))");

	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

	}

}

Student.java

package domain;

public class Student {

	private String id;
	private String name;
	private String sex;

	public Student() {
		super();

	}
	public Student(String id, String name, String sex) {
		super();
		this.id = id;
		this.name = name;
		this.sex = sex;
	}
	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + ", sex=" + sex + "]";
	}
	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 getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}


}

activity_main.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"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <EditText
        android:id="@+id/ed_name"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:hint="请输入学生的姓名" />

    <RadioGroup
        android:id="@+id/rgb"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal" >

        <RadioButton
            android:id="@+id/male"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:checked="true"
            android:text="男" />

        <RadioButton
            android:id="@+id/female"
            android:layout_width="0dip"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="女" />
    </RadioGroup>

    <Button
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:onClick="save"
        android:text="保存" />

    <ListView
        android:id="@+id/lv"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" >
    </ListView>

</LinearLayout>

item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >
    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content">
	    <ImageView
	        android:layout_marginLeft="15dip"
	        android:layout_alignParentLeft="true"
	        android:id="@+id/item_iv"
	        android:layout_width="20dip"
	        android:layout_height="30dip"
		    android:layout_centerVertical="true"
	        />
		<TextView
		    android:layout_toRightOf="@id/item_iv"
		    android:id="@+id/item_tv"
		    android:layout_width="wrap_content"
		    android:layout_height="wrap_content"
		    android:layout_centerVertical="true"
		    />
		<ImageView
		    android:layout_marginRight="8dip"
		    android:id="@+id/item_delete"
		    android:layout_centerVertical="true"
		    android:layout_alignParentRight="true"
		    android:src="@drawable/delete"
		    android:layout_width="wrap_content"
		    android:layout_height="wrap_content"
		    />
	</RelativeLayout>
</LinearLayout>

• 常见的对话框

activity_main.xml

   <Button
        android:onClick="dialog01"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="创建确认取消对话框"/>

    <Button
        android:onClick="dialog02"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="创建单选对话框"/>

    <Button
        android:onClick="dialog03"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:text="创建多选对话框"/>

MainActivity.java

    //创建确认取消对话框
    public void dialog01(View v){
    	AlertDialog.Builder builder = new AlertDialog.Builder(this);

    	builder.setTitle("约会吗?");
    	builder.setMessage("告别单身,你愿意吗?");

    	//愿意情况下开启监听器
    	builder.setPositiveButton("愿意", new DialogInterface.OnClickListener() {

			@Override
			public void onClick(DialogInterface dialog, int which) {
				Toast.makeText(MainActivity.this, "我也单身,说不定可以来找我", 0).show();

			}
		});
    	builder.setNegativeButton("不愿意", null);
    	builder.show();
    }

    //创建单选进度条
    public void dialog02(View v){
    	AlertDialog.Builder builder = new AlertDialog.Builder(this);
    	builder.setTitle("单选对话框");
    	final String[] items = {"小樱","小明","诸葛亮"};
    	builder.setSingleChoiceItems(items, -1, new DialogInterface.OnClickListener() {

			@Override
			public void onClick(DialogInterface dialog, int which) {
				Toast.makeText(MainActivity.this, "被点击了:"+items[which]+",位置:"+which, 0).show();
			}
		});
    	builder.show();
    }

    //创建多选对话框
    public void dialog03(View v){
    	AlertDialog.Builder builder = new AlertDialog.Builder(this);
    	builder.setTitle("多选框");

    	final String[] items ={"android","python","go","c/c++"};
    	boolean[] checkItems = {true,false,false,true};

    	builder.setMultiChoiceItems(items, checkItems, new DialogInterface.OnMultiChoiceClickListener() {

			@Override
			public void onClick(DialogInterface dialog, int which, boolean isChecked) {
				Toast.makeText(MainActivity.this, " 被点击了 : " + items[which] +",位置: " +which+", 值是: "+ isChecked, 0	).show();

			}
		});
    	builder.show();
    }

• 用ContentValues来实现增删改查

Student.java

package domain;

public class Student {
	private String id;
	private String name;
	private String sex;


	public Student() {
		super();
		// TODO Auto-generated constructor stub
	}
	public Student(String id, String name, String sex) {
		super();
		this.id = id;
		this.name = name;
		this.sex = sex;
	}
	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 getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	@Override
	public String toString() {
		return "Student [id=" + id + ", name=" + name + ", sex=" + sex + "]";
	}

}

StudentDao.java

package com.example.studentsystemdemo3;

import domain.Student;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;

/*
 *
 *   增删改查有两套api了
 *   	
 *   第一套(你经常使用的):
 *   	增删改:db.execSQL();
 *   	查询:db.rawQuery();
 *   
 *   第二套(推荐使用):
 *   
 *   	增:db.insert();
 *   	删:db.delete();
 *      改:db.update();
 *      查询:db.query();
 * 		
 * 	实际开发过程中:数据库到底用的多不多?不多 ...
 *
 * 	提供的保存数据的方式很多 :
 *
 * 		保存数据的方式 :
 * 			1. 应用内部的私有的文件夹下 :  /data/data/net.itceo.hello/files/cache
 * 			2. sharedPreference :  /data/data/net.itceo.hello/shar_prefs
 * 			3. 在 sd 卡公共的部分 :  /mnt/sdcard
 * 			4. 存到数据库 中  : sqlite 数据库
 *
 * 	
 * 	
 *
 */
public class StudentDao {
StudentDbOpenHelper helper;

	public StudentDao(Context context){

		helper = new StudentDbOpenHelper(context);
	}
	public void add(Student st){
		//拿到 工具类的实例 , 然后去操作 数据库
				SQLiteDatabase db = helper.getWritableDatabase();
				ContentValues values = new ContentValues();
				values.put("name", st.getName());
				values.put("sex", st.getSex());
				db.insert("students", null, values);

	}

	public void delete(String id){

		SQLiteDatabase db = helper.getWritableDatabase();
		db.delete("students", "_id=?", new String[]{id});
	}

	public void update(Student st){

		SQLiteDatabase db = helper.getWritableDatabase();

		ContentValues values = new ContentValues();
		values.put("name", st.getName());
		values.put("sex", st.getSex());
		db.update("students", values, "_id=?", new String[]{st.getId()});
	}

	public Student find(String id){

		SQLiteDatabase db = helper.getReadableDatabase();
db.query("students", new String[]{"_id","name","sex"}, "_id=?", new String[]{id}, null, null, null);

		Cursor cursor = db.rawQuery("select * from students where _id=?", new String[]{id});

		boolean result = cursor.moveToNext();

		Student st = null;
		if(result){
			int _id = cursor.getInt(cursor.getColumnIndex("_id"));
			String name = cursor.getString(cursor.getColumnIndex("name"));
			String sex =  cursor.getString(cursor.getColumnIndex("sex"));

			st = new Student(String.valueOf(_id),name,sex);

		}

		// 最后会释放 资源
		cursor.close();

		return st;
	}

}

StudentDbOpenHelper.java

package com.example.studentsystemdemo3;

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

public class StudentDbOpenHelper extends SQLiteOpenHelper {

	public StudentDbOpenHelper(Context context){
		super(context, "student.db", null, 1);
	}
	@Override
	public void onCreate(SQLiteDatabase db) {
		//创建数据库
		db.execSQL("create table students (_id integer primary key autoincrement, name varchar(30),sex varchar(10))");
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

	}

}

TestStudentDao.java

package com.example.studentsystemdemo3;

import domain.Student;
import android.test.AndroidTestCase;

public class TestStudentDao extends AndroidTestCase {
	public void testAdd(){
		Student st = new Student("8798", "二球", "女");

		StudentDao sdao = new StudentDao(getContext());
		sdao.add(st);
	}
}

//注意:写测试类需要在AndroidMainfest.xml 下声明instrumentation和uses-libray