Question

我已经通过一些sqlite教程并自己编写了这段代码来强化原理。我在几个方面经历的教程各不相同，所以这就是我提出的所有内容的组合。

除了下面列出的两个类之外，我所拥有的只是一个添加，删除，插入，更新和显示数据库数据的活动。

我正在寻求任何反馈。但是我有一些具体的问题。提前谢谢。

我应该何时关闭帮助程序类或自动处理垃圾回收？
我应该创建一个Boxer POJO（普通的旧java对象来传递和传出来自DAO的拳击手数据吗？
DAO实施是否有效？
代码是否偏离了Java和Android最佳实践？
欢迎任何建设性意见

助手类

public class BoxScoresHelper extends SQLiteOpenHelper {

    private static final String DB_NAME = "boxing_scores.db";
    private static final int VERSION = 1;
    private static BoxScoresHelper instance = null;

    public static BoxScoresHelper getInstance(Context context){

        if(instance == null){

            instance = new BoxScoresHelper(context);

        }

        return instance;
    }

    private BoxScoresHelper(Context context) {
        super(context, DB_NAME, null, VERSION);



    }

    @Override
    public void onCreate(SQLiteDatabase db) {

        db.execSQL(createBoxerSQLString());

    }

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

        db.execSQL("Drop Table If Exists " + BoxerDAO.TABLE_NAME);
        onCreate(db);

    }

    private String createBoxerSQLString(){

        String boxerCreateString = "create table " + BoxerDAO.TABLE_NAME +
                "(" + BoxerDAO._ID + " Integer Primary Key AutoIncrement, " +
                BoxerDAO.BOXER_NAME +  " Text Not Null, " +
                BoxerDAO.WEIGHT_CLASS + " Text Not Null, " +
                BoxerDAO.WINS + " Integer Not Null, " +
                BoxerDAO.LOSSES + " Integer Not Null);";


        return boxerCreateString;
    }

}

DAO课程

public class BoxerDAO {

    public static final String TABLE_NAME = "Boxer";
    public static final String _ID  = "_id";
    public static final String BOXER_NAME = "boxer_name";
    public static final String WEIGHT_CLASS = "weight_class";
    public static final String WINS = "wins";
    public static final String LOSSES ="losses";

    private final BoxScoresHelper myScoresHelper;
    private SQLiteDatabase myBoxerDB;

    public BoxerDAO(Context context){

        myScoresHelper = BoxScoresHelper.getInstance(context);

    }

    public Cursor query(String[] projection,String selection,String[] selectionArgs, String orderBy){

        Cursor cursor;
        myBoxerDB = myScoresHelper.getReadableDatabase();

        cursor = myBoxerDB.query(TABLE_NAME, projection, selection, selectionArgs, null, null, orderBy);

        //myBoxerDB.close();

        return cursor;


    }

    public Cursor queryAll(){

        Cursor cursor;
        myBoxerDB = myScoresHelper.getReadableDatabase();

        cursor = myBoxerDB.rawQuery("Select * From " + TABLE_NAME, null);

        //myBoxerDB.close();
        return cursor;

    }

    public int delete(int id){

        int rowsDel;
        myBoxerDB = myScoresHelper.getWritableDatabase();

        rowsDel = myBoxerDB.delete(TABLE_NAME, _ID + " = " + id , null);

        //myBoxerDB.close();
        return rowsDel;

    }

    public long insert(ContentValues values){

        long insertId = -1;

        myBoxerDB = myScoresHelper.getWritableDatabase();

        insertId = myBoxerDB.insert(TABLE_NAME, null, values);

        //myBoxerDB.close();

        return insertId;

    }

    public int update(ContentValues values,String selection, String[] selectionArgs){

        int updatedRows;
        myBoxerDB = myScoresHelper.getWritableDatabase();

        updatedRows = myBoxerDB.update(TABLE_NAME, values, _ID + " = " + selection, selectionArgs);
        //myBoxerDB.close();

        return updatedRows;

    }   

}

Android SQLite代码反馈

0 个答案: