SQLite Databases 数据存储

0 SQLiteDatabases数据库特点

一种切入式关系型数据库，支持事务，可使用SQL语言，独立，无需服务。程序内通过类名可访问数据库，程序外不可以访问。

SQLiteDatabases数据库使用方法

1 创建数据库及表，使用 SQLiteOpenHelper 类

 public class DBHelper extends SQLiteOpenHelper {     private static final String DATABASE_NAME = "zc.db";//数据库名称
     public static final String TANLE_NAME = "car";//表名
     private static final int DATABASE_VERSION = 1;//数据库版本     public DBHelper(Context context) {
         super(context, DATABASE_NAME, null, DATABASE_VERSION);
     }     //数据库第一次被创建时执行此方法，创建表
     @Override
     public void onCreate(SQLiteDatabase db) {
         db.execSQL("create table if not exists" + TANLE_NAME +
                 "(_id integer primary key autoincrement ,brandName varchar ,brandId integer ,logo text)");
     }     //如果DATABASE_VERSION改为2，系统发现现有数据库版本不同,即会调用onUpgrade
     @Override
     public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
         db.execSQL("ALTER TABLE" + TANLE_NAME + " ADD COLUMN other text");
     } }

2 操作SQLite数据库表，使用SQLiteDatabase类

SQLiteDatabase 增删改查方法

第一种：execSQL() , rawQuery() ,要求sql语法熟练

第二张：insert()，update()，deleter()，query()

 public class DBManager {     private final DBHelper dbHelper;//DBHelper对象
     private final SQLiteDatabase db;//SQLiteDatabase对象     public DBManager(Context context) {
         dbHelper = new DBHelper(context);
         db = dbHelper.getWritableDatabase();//真正创建或打开数据库，获取可读写SQLiteDatabase对象
     }     //添加车辆列表
     public void addCarList(List<Car> carList) {
         db.beginTransaction();
         try {
             for (Car car : carList) {
                 add(car);
             }
             db.setTransactionSuccessful();
         } finally {
             db.endTransaction();
         }
     }     //新增
     public void add(Car car) {
         ContentValues cv = new ContentValues();
         cv.put("brandId", car.getBrandId());
         cv.put("brandName", car.getBrandName());
         cv.put("logo", car.getLogo());
         //rowid 返回新添记录的行号，与主键id无关
         long rowid = db.insert(DBHelper.TANLE_NAME, null, cv);
         db.close();
     }     //删除
     public void delete(String brandId) {
         db.delete(DBHelper.TANLE_NAME, "brandId = ? ", new String[]{brandId});
         db.close();
     }     //修改
     public void update(Car car) {
         ContentValues cv = new ContentValues();
         cv.put("brandName", car.getBrandName());
         db.update(DBHelper.TANLE_NAME, cv, "brandId = ? ", new String[]{car.getBrandId()});
         db.close();
     }     //查询
     public List<Car> queryList() {
         List<Car> list = new ArrayList<>();
         Cursor cursor = db.rawQuery("select * from " + DBHelper.TANLE_NAME, null);
         while (cursor.moveToNext()) {
             Car car = new Car();
             car.setBrandId(cursor.getString(cursor.getColumnIndex("brandId")));
             car.setBrandName(cursor.getString(cursor.getColumnIndex("brandName")));
             car.setLogo(cursor.getString(cursor.getColumnIndex("logo")));
             list.add(car);
         }
         cursor.close();
         db.close();
         return list;
     }     public Car queryCar(String brandId) {
         Car car = new Car();
         Cursor cursor = db.rawQuery("select * from " + DBHelper.TANLE_NAME + " where brandId = ? ", new String[]{brandId});
         while (cursor.moveToNext()) {
             car.setBrandId(cursor.getString(cursor.getColumnIndex("brandId")));
             car.setBrandName(cursor.getString(cursor.getColumnIndex("brandName")));
             car.setLogo(cursor.getString(cursor.getColumnIndex("logo")));
         }
         cursor.close();
         db.close();
         return car;
     } }