Android 原生SQLite数据库操作实战

• 创建DB工具类

  MyDBHelper.java(创建数据库的操作)

  package com.amos.android_db;
  import android.content.Context;
  import android.database.sqlite.SQLiteDatabase;
  import android.database.sqlite.SQLiteOpenHelper;
  
  /**
   * Created by amosli on 14-6-12.
   */
  public class MyDBHelper extends SQLiteOpenHelper{
      /**
       *
       * @param context
       */
      public MyDBHelper(Context context) {
          super(context, "sqlitedb", null, 1);
      }
  
      /**
       * 数据库第一次创建的时候调用此方法
       * @param db
       */
      @Override
      public void onCreate(SQLiteDatabase db) {
          db.execSQL("create table if not exists person (personid integer primary key autoincrement ,name varchar(30) ,age integer(3) )");
      }
  
      @Override
      public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
      }
  }
  

• PersonDao.java (实现增删改查)

  package com.amos.android_db.dao;
  
  import android.content.ContentValues;
  import android.content.Context;
  import android.database.Cursor;
  import android.database.sqlite.SQLiteDatabase;
  import android.util.Log;
  import com.amos.android_db.MyDBHelper;
  
  import java.util.ArrayList;
  import java.util.List;
  
  /**
   * Created by amosli on 14-6-12.
   */
  public class PersonDao {
      private Context context;
      MyDBHelper dbHelper;
  
      public PersonDao(Context context) {
          this.context = context;
          dbHelper = new MyDBHelper(context);
      }
  
      /**
       * 添加一条记录
       */
      public void add(String name, int age) {
          SQLiteDatabase db = dbHelper.getWritableDatabase();
          if (db.isOpen()) {
              ContentValues values = new ContentValues();
              values.put("age", age);
              values.put("name", name);
              //不允许插入一个空值,如果contentvalue,一般第二个参
              db.insert("person", null, values);//通过组拼完成的添加的操作
          }
          db.close();
      }
  
  }
  

• 测试添加方法

  public void testAdd() throws Exception{
          PersonDao personDao = new PersonDao(this.getContext());
          personDao.add("amosli",10);
          personDao.add("amosli",10);
          for(int i=0;i<10;i++){
              personDao.add("amos"+i,10+i);
          }
      }
  

• 删除数据
  delete方法,主要是调用了SQLiteDatabase的delete方法.其实质上也是在拼sql语句.

  public void delete(String name) {
          SQLiteDatabase db = dbHelper.getWritableDatabase();
          if (db.isOpen()) {
              db.delete("person", "name=?", new String[]{name});
              db.close();
          }
      }
      //测试 delete方法：
      public void testDelete() throws Exception{
              PersonDao personDao = new PersonDao(this.getContext());
              personDao.delete("amosli");
          }
  

• 更新数据

public void update(String name, String newname, int newage) {
        SQLiteDatabase db = dbHelper.getWritableDatabase();

        if (db.isOpen()) {
            ContentValues contentValues = new ContentValues();
            contentValues.put("name", newname);
            contentValues.put("age", newage);
            db.update("person", contentValues, "name=?", new String[]{name});
            db.close();
        }
    }
    //测试update
    public void testUpdate() throws Exception{
            PersonDao personDao = new PersonDao(this.getContext());
            personDao.update("amos0","0amos",35);
     }

• 查询数据

public boolean find(String name) {
        boolean status_result = false;

        SQLiteDatabase db = dbHelper.getReadableDatabase();
//        public android.database.Cursor query(
//                String table,
//                String[] columns,
//                String selection,
//                String[] selectionArgs,
//                String groupBy,
//                String having,
//                String orderBy)

        if (db.isOpen()) {
            Cursor cursor = db.query("person", null, "name=?", new String[]{name}, null, null, null);
            if (cursor.moveToFirst()) {
                status_result = true;
            }
            cursor.close();
            db.close();
        }
            return status_result;
        }
        
//测试select
 	public void testFind() throws Exception{
            PersonDao personDao = new PersonDao(this.getContext());
            assertEquals(true,personDao.find("amos1"));
        }       

• 查询所有数据

public List findAll(){
         List persons = null;
         SQLiteDatabase db = dbHelper.getReadableDatabase();
         if(db.isOpen()){
             persons = new ArrayList();

             Cursor cursor = db.query("person", null, null, null, null, null, null);

             while(cursor.moveToNext()){
                 Person person = new Person();
                 person.setName(cursor.getString(cursor.getColumnIndex("name")));
                 person.setAge(cursor.getInt(cursor.getColumnIndex("age")));
                 persons.add(person);
              }
             cursor.close();
             db.close();
         }
         return persons;
     }
 // 测试
public void testFindAll() throws Exception{
            PersonDao personDao = new PersonDao(getContext());
            List personList = personDao.findAll();
            for(Person person:personList){
                Log.d("person:",person.toString());
            }

        }

• 扩展 （事务）
  这里以amos1向amos2转钱200元为例:

  1),amos1账户初始1000元,amos2账户初始0元.

  2),从amos1中减去200元,amos2中加上200元,这两个步骤要么同时成功,要么同时失败,不能一方成功,另一主失败,这就是事务.

  代码实现：升级数据库

  package com.amos.android_db;
  
  import android.content.Context;
  import android.database.sqlite.SQLiteDatabase;
  import android.database.sqlite.SQLiteOpenHelper;
  
  /**
   * Created by amosli on 14-6-12.
   */
  public class MyDBHelper extends SQLiteOpenHelper{
     
      public MyDBHelper(Context context) {
          super(context, "sqlitedb", null, 2);
      }
  
      /**
       * 数据库第一次创建的时候调用此方法
       * @param db
       */
      @Override
      public void onCreate(SQLiteDatabase db) {
          db.execSQL("create table if not exists person (personid integer primary key autoincrement ,name varchar(30) ,age integer(3) )");
      }
  
      @Override
      public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
          db.execSQL("alter table person add account integer null");
      }
  }
  

  在初始化时更新表的结构,添加account一列,用来表示账户余额.

  在PersonDao中添加如下方法:

  public void transferMoney() {
          SQLiteDatabase db = dbHelper.getWritableDatabase();
          if(db.isOpen()){
              try{
  
                  db.beginTransaction();
  
                  //给amos1账户里设置1000元,amost account=0;
                  db.execSQL("update person  set account=?  where name = ?",new Object[]{1000,"amos1"});
                  db.execSQL("update person  set account=?  where name = ?",new Object[]{0,"amos2"});
  
                  //从amos1账户里扣除200元
                  db.execSQL("update person  set account=account-?  where name = ?",new Object[]{200,"amos1"});
                  //把amos1的钱转给amos2
                  db.execSQL("update person set account=account+? where name=?",new Object[]{200,"amos2"});
  
              }catch(Exception e){
                  e.printStackTrace();
              }finally{
                  //显示的设置数据事务是否成功
                  db.setTransactionSuccessful();
                  db.endTransaction();
  
                  db.close();
              }
          }
  
  
      }
  

  这里先beginTransaction,然后要注意的是setTransactionSuccessful和endTransaction.

  public void testTransaction() throws Exception{
              PersonDao personDao = new PersonDao(getContext());
              personDao.transferMoney();
          }