android SQLiteOpenHelper 使用

1、实体

package mydemo.mycom.demo2.entity;

public class UserInfo {
    private int id;
    private String username;
    private String password;

    public UserInfo()
    { }

    public UserInfo(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    public int getId() {
        return id;
    }

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

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }
}

2.UserSQLiteOpenHelper

package mydemo.mycom.demo2.db;

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

public class UserSQLiteOpenHelper extends SQLiteOpenHelper {

    /**
     * 数据库的构造方法  用来定义数据库的名称  数据库查询的结果集 数据库的版本
     * **/

    public UserSQLiteOpenHelper(Context context) {
        super(context, "user.db", null, 1);
    }
    /**
     * 数据库第一次被创建的时候调用的方法
     *  db被创建的数据库
     * **/
    @Override
    public void onCreate(SQLiteDatabase db) {
        //初始化数据库的表结构 d integer primary key autoincrement,
        db.execSQL("create table user (id integer primary key autoincrement,username varchar(20),password varchar(20))");
    }
    /**
     * 当数据库的版本号发生变化的时候(增加的时候) 调用
     * */
    @Override
    public void onUpgrade(SQLiteDatabase db, int i, int i2) {

        db.execSQL("alter table user add account varchar(20)");
    }
}

3.JDBC的UserDAO

package mydemo.mycom.demo2.dao;

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

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

import mydemo.mycom.demo2.db.UserSQLiteOpenHelper;
import mydemo.mycom.demo2.entity.UserInfo;

public class UserDao {

    private UserSQLiteOpenHelper helper;

    public UserDao(Context context)
    {
        helper = new UserSQLiteOpenHelper(context);
    }

    /**
    * 添加一条记录到数据库
     * username 用户名
     * password 密码
     *
    * */
    public void add(String username,String password)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("insert into user(username,password) values(?,?)",new String[]{username,password});
        db.close();

    }

    /**
     * 判断数据库是否存在username 的数据
     *
     * username 用户名
     * */
    public boolean findByUsername(String username)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        Cursor cursor = db.rawQuery("select * from user where username=?",new String[]{username});
        boolean result = cursor.moveToNext();
        db.close();
        return result;
    }

    /**
     * 修改一条记录
     * 通过username 修改 password
     *
     * username 用户名
     * password 密码
     *
     * */
    public void update(String username,String password)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("update user set password=? where username=?",new String[]{password,username});
        db.close();

    }

    /**
     * 删除记录
     * 通过username修改一条记录
     *
     * username 用户名
     * */
    public void delete(String username)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        db.execSQL("delete from user where username=?",new String[]{username});
        db.close();
    }

    /**
     * 找出所有用户信息
     * */
    public List<UserInfo> findAll()
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        List<UserInfo> list = new ArrayList<UserInfo>();
        Cursor cursor = db.rawQuery("select * from user",null);
        while(cursor.moveToNext())
        {
            int id = cursor.getInt(cursor.getColumnIndex("id"));
            String username = cursor.getString(cursor.getColumnIndex("username"));
            String password = cursor.getString(cursor.getColumnIndex("password"));

            UserInfo userInfo = new UserInfo(id,username,password);
            list.add(userInfo);
        }
        cursor.close();
        db.close();
        return list;
    }

    /**
     * 通过id 用户信息
     * id 用户id
     * */
    public UserInfo findById(int id)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        Cursor cursor =db.rawQuery("select * from user where id=?",new String[]{id+""});

        UserInfo user = new UserInfo();

        while(cursor.moveToNext())
        {
            int uid = cursor.getInt(cursor.getColumnIndex("id"));
            String username = cursor.getString(cursor.getColumnIndex("username"));
            String password = cursor.getString(cursor.getColumnIndex("password"));

            user.setId(uid);
            user.setPassword(password);
            user.setUsername(username);

            break;
        }
        cursor.close();
        db.close();
        return user;

    }

}

4.SQLiteOpenHelper的 UserDAO

package mydemo.mycom.demo2.dao;

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

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

import mydemo.mycom.demo2.db.UserSQLiteOpenHelper;
import mydemo.mycom.demo2.entity.UserInfo;

/**
 * Created by Administrator on 2015/5/15.
 */
public class UserDao2 {

    private UserSQLiteOpenHelper helper;

    public UserDao2(Context context)
    {
        helper = new UserSQLiteOpenHelper(context);
    }

    /**
     * 添加一条记录到数据库
     * username 用户名
     * password 密码
     *
     * */
    public long add(String username,String password)
    {
        SQLiteDatabase db = helper.getWritableDatabase();

        ContentValues values = new ContentValues();

        values.put("username",username);
        values.put("password",password);

        long num = db.insert("user",null,values);

        db.close();

        return num;
    }

    /**
     * 判断数据库是否存在username 的数据
     *
     * username 用户名
     * */
    public boolean findByUsername(String username)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        Cursor cursor = db.query("user",null,"username=?",new String[]{username},null,null,null);
        boolean result = cursor.moveToNext();
        db.close();
        return result;
    }

    /**
     * 修改一条记录
     * 通过username 修改 password
     *
     * username 用户名
     * password 密码
     *
     * */
    public int update(String username,String password)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put("password",password);
        int num = db.update("user",values,"username=?", new String[]{username});
        db.close();
        return num;
    }

    /**
     * 删除记录
     * 通过username修改一条记录
     *
     * username 用户名
     * */
    public int delete(String username)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        int num = db.delete("user","username=?",new String[]{username});
        db.close();
        return num;
    }

    /**
     * 找出所有用户信息
     * */
    public List<UserInfo> findAll()
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        List<UserInfo> list = new ArrayList<UserInfo>();
        Cursor cursor = db.query("user",null,null,null,null,null,null);
        while(cursor.moveToNext())
        {
            int id = cursor.getInt(cursor.getColumnIndex("id"));
            String username = cursor.getString(cursor.getColumnIndex("username"));
            String password = cursor.getString(cursor.getColumnIndex("password"));

            UserInfo userInfo = new UserInfo(id,username,password);
            list.add(userInfo);
        }
        cursor.close();
        db.close();
        return list;
    }

    /**
     * 通过id 用户信息
     * id 用户id
     * */
    public UserInfo findById(int id)
    {
        SQLiteDatabase db = helper.getWritableDatabase();
        Cursor cursor = db.query("user",null,"id=?",new String[]{id+""},null,null,null);

        UserInfo user = new UserInfo();

        while(cursor.moveToNext())
        {
            int uid = cursor.getInt(cursor.getColumnIndex("id"));
            String username = cursor.getString(cursor.getColumnIndex("username"));
            String password = cursor.getString(cursor.getColumnIndex("password"));

            user.setId(uid);
            user.setPassword(password);
            user.setUsername(username);

            break;
        }
        cursor.close();
        db.close();
        return user;

    }
}

5.SQLiteOpenHelper 简单使用

package mydemo.mycom.demo2;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.text.TextUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;

import mydemo.mycom.demo2.dao.UserDao;
import mydemo.mycom.demo2.dao.UserDao2;

public class Register extends ActionBarActivity implements View.OnClickListener {

    private EditText et_register_username;
    private EditText et_register_password;
    private Button btn_register;

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

        et_register_username = (EditText)findViewById(R.id.et_register_username);
        et_register_password = (EditText)findViewById(R.id.et_register_password);
        btn_register = (Button)findViewById(R.id.btn_register);
        btn_register.setOnClickListener(this);

    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_register, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public void onClick(View view) {

        String username = et_register_username.getText().toString().trim();
        String password = et_register_password.getText().toString().trim();
        if(TextUtils.isEmpty(username) || TextUtils.isEmpty(password))
        {
            Toast.makeText(this,"用户名和密码不能为空",Toast.LENGTH_SHORT).show();
            return;
        }
        UserDao2 userDao = new UserDao2(this);
        userDao.add(username,password);
        Toast.makeText(this,"注册成功",Toast.LENGTH_SHORT).show();

    }
}

6.SQLiteOpenHelper事务管理

package mydemo.mycom.demo2.testUserDao;

import android.database.sqlite.SQLiteDatabase;
import android.test.AndroidTestCase;

import mydemo.mycom.demo2.db.UserSQLiteOpenHelper;

public class TestUserInfo extends AndroidTestCase{
    private String s;
    public void testTransaction() throws Exception
    {
        UserSQLiteOpenHelper helper = new UserSQLiteOpenHelper(getContext());
        SQLiteDatabase db = helper.getWritableDatabase();
        //开始数据库的事务
        db.beginTransaction();
        try{
            db.execSQL("update user set account=account-1000 where id=1");
            //空指针异常
            s.equals("123");
            db.execSQL("update user set account=account+1000 where id=2");
            //提交事务
            db.setTransactionSuccessful();
        }
        catch(Exception ex)
        {
        }
        finally
        {
            //结束事务
            db.endTransaction();
            db.close();
        }
    }

}