Android开发三：数据库设计及应用(一)

SqlLite

public class DBHelper {
    
	public static final String DB_DBNAME = "scanner";//数据库名称

	public static final String DB_TABLENAME = "product";//数据表名称

	public static final int VERSION = 4;//版本 更新的时候有用,一般无用

	public static SQLiteDatabase dbInstance;

	private MyDBHelper myDBHelper;//帮助类,创建表字段

	private StringBuffer tableCreate;

	private Context context;
	
	public DBHelper(Context context)
	{
		this.context = context;
	}
	
	public void openDatabase() {
                //创建数据库
                 if (dbInstance == null) {
			myDBHelper = new MyDBHelper(context, DB_DBNAME, VERSION);
			dbInstance = myDBHelper.getWritableDatabase();
		}
    }
	
	
	/**
	 * 往数据库里面的product表插入一条数据，若失败返回-1
	 * 
	 * @param user
	 * @return 失败返回-1
	 */
	public long insert(Model model) {
		ContentValues values = new ContentValues();
		values.put("productName", model.productName);
		values.put("productType", model.productType);
		return dbInstance.insert(DB_TABLENAME, null, values);
	}
	/**
	 * 修改数据库中的一条记录
	 * 
	 * @param user
	 */
	public void modify(Model model) {
		ContentValues values = new ContentValues();
		values.put("productName", model.productName);
		values.put("productType", model.productType);
		dbInstance.update(DB_TABLENAME, values, "_id=?",
				new String[] { String.valueOf(model._id) });
	}
	/**
	 * 删除数据库中的一条记录
	 * 
	 * @param user
	 */
	public void delete(int _id) {
		dbInstance.delete(DB_TABLENAME, "_id=?",
				new String[] { String.valueOf(_id) });
	}

	/**
	 * 获得数据库中所有的用户，将每一个用户放到一个map中去，然后再将map放到list里面去返回
	 * 
	 * @return list
	 */
	public ArrayList> getAllUser() {
		ArrayList> list = new ArrayList>();
		Cursor cursor = null;
		
			cursor = dbInstance.query(DB_TABLENAME, new String[] { "_id",
					"productName", "productType" }, null, null, null,
					null, null);
		

		while (cursor.moveToNext()) {
			HashMap item = new HashMap();
			item.put("_id", cursor.getInt(cursor.getColumnIndex("_id")));
			item.put("productName", cursor.getString(cursor.getColumnIndex("productName")));
			item.put("productType",
					cursor.getString(cursor.getColumnIndex("productType")));
			list.add(item);
		}
		return list;
	}
class MyDBHelper extends SQLiteOpenHelper {

	public MyDBHelper(Context context, String name, int version) {
		super(context, name, null, version);
	}

	@Override
	public void onCreate(SQLiteDatabase db) {
		//create table 
		tableCreate = new StringBuffer();
		tableCreate.append("create table ").append(DB_TABLENAME)
				.append(" (")
				.append("_id integer primary key autoincrement,")
				.append("productName text,").append("productType text")
				.append(")");
		System.out.println(tableCreate.toString());
		db.execSQL(tableCreate.toString());
	}

	@Override
	public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
		String sql = "drop table if exists " + DB_TABLENAME;
		db.execSQL(sql);
		myDBHelper.onCreate(db);
	}

    }
}