为什么我的Android SQLite数据库有时无法加载数据库中的所有对象？

我使用SQLite来存储一些对象，然后显示在列表视图中。当活动启动时，我只需抓取数据库中的所有对象，并使用结果填充列表视图。偶尔（约5％的时间），我注意到并非所有结果都从数据库返回。我一直只对1结果感到害羞，而且，如果我重新加载活动，则会正确加载缺失的结果。为什么我的Android SQLite数据库有时无法加载数据库中的所有对象？

在试图追踪问题时，我记录了Cursor对象计数后查询并注意到当结果丢失时，它也从Cursor对象中丢失（所以问题不在于使返回的对象膨胀）。有没有人有任何这个问题的经验？

下面是我存储在我的数据库中的一个对象的示例。

public class MyObject { 
    public static final String DB_TABLE = "object"; 
    public static final int DB_VERSION = 1; 

    public static final String COL_ID = "id"; 
    public static final String COL_TITLE = "title"; 
    public static final String COL_SUBTITLE = "subtitle"; 
    public static final String COL_DESCRIPTION = "description"; 
    public static final String COL_START_TIME = "start_time"; 
    public static final String COL_END_TIME = "end_time"; 
    public static final String COL_IMAGE1 = "background_image"; 
    public static final String COL_IMAGE2 = "icon_image"; 
    public static final String COL_EXTRAS = "extras"; 

    public static final String DB_CREATE = String.format("create table if not exists %1$s (%2$s text primary key, %3$s text, %4$s text, %5$s text, %6$s integer, %7$s integer, %8$s text, %9$s text, %10$s integer);", 
     DB_TABLE, COL_ID, COL_TITLE, COL_SUBTITLE, COL_DESCRIPTION, COL_START_TIME, COL_END_TIME, COL_IMAGE1, COL_IMAGE2, COL_EXTRAS); 
    public static final String [] DB_COLUMNS = new String [] {COL_ID, COL_TITLE, COL_SUBTITLE, COL_DESCRIPTION, COL_START_TIME, COL_END_TIME, COL_IMAGE1, COL_IMAGE2, COL_EXTRAS}; 

    public String Id; 
    public String Title; 
    public String Subtitle; 
    public String Description; 
    public long StartTime; 
    public long EndTime; 
    public String Image2; 
    public String Image2; 
    public int Extras; 

    public Event() {} 

    public static DataBaseHelper getDBHelper(Context context) { 
      return new DataBaseHelper(context, QmobixConferenceApplication.DB_NAME, DB_VERSION, DB_CREATE, DB_TABLE, COL_ID); 
    } 
}

而且DataBaseHelper有关块...

public class DataBaseHelper extends SQLiteOpenHelper { 
    private static final String TAG = "DataBaseHelper"; 

    private SQLiteDatabase mDB; 
    private String mSQL; 
    private String mDBName; 
    private String mTableName; 
    private String mKeyId; 
    private boolean isClosed = false; 

    public DataBaseHelper(Context context, String DBName, int version, String sql, String tableName, String keyId) throws SQLiteException { 
     super(context, DBName, null, version); 
     this.mSQL = sql; 
     this.mDBName = DBName; 
     this.mTableName = tableName; 
     this.mKeyId = keyId; 
     try { 
      mDB = this.getWritableDatabase(); 
      mDB.execSQL(mSQL); 
     } catch(SQLiteException ex) { 
      Log.e(TAG, String.format("Could not create and/or open the database [ %1$s ]", mDBName), ex); 
      throw ex; 
     } 
    } 

    @Override 
    public void onCreate(SQLiteDatabase db) { 
     try { 
      db.execSQL(mSQL); 
     } catch(SQLException ex) { 
      Log.e(TAG, String.format("Could not create table according to SQL [ %1$s }", mSQL), ex); 
     } 
    } 

    @Override 
    public synchronized void close() { 
     super.close(); 
     if(mDB != null) { 
      mDB.close(); 
     } 
     isClosed = true; 
    } 

    public Cursor get(String [] columns, String orderBy) { 
     return mDB.query(mTableName, columns, null, null, null, null, orderBy); 
    } 
}

现在为例加载从我的数据库对象。

DataBaseHelper db = null; 
    Cursor cursor = null; 
    try { 
     db = MyObject.getDBHelper(mContext); 
     cursor = db.get(MyObject.DB_COLUMNS, String.format("%1$s ASC", MyObject.COL_START_TIME)); 
    } catch(Exception ex) { 
     // bad news 
    } finally { 
     if(cursor != null) { cursor.close(); } 
     if(db != null) { db.close(); } 
    }

我知道很多东西需要阅读。希望以前有人看到过，这只是我在DataBaseHelper中做了一些工作。我很感谢您提供的任何建议或建议。谢谢！

来源

2012-01-05 rposky

尝试使用下面的代码在这里我正在创建列表添加此列表到您的列表视图。

ArrayList results= new ArrayList(); 
    SQLiteDatabase myDB = this.openOrCreateDatabase("dummy.db", SQLiteDatabase.OPEN_READWRITE, null); 
     try{ 
       Cursor c = myDB.rawQuery("select a from xyz", null); 
       int Column1 = c.getColumnIndex("a"); 


      // Check if our result was valid. 
      c.moveToFirst(); 
      if (c != null) { 
       int i = 0; 
       // Loop through all Results 
       do { 
        i++; 
       String a= c.getString(Column1); 

       results.add(a); 
        } while (c.moveToNext()); 
        } 


      } catch (SQLiteException e) { 
       e.printStackTrace(); 
      } finally { 
       if (myDB != null) 
         myDB.close(); 
      }

来源

2012-01-06 11:26:55 Vamshi

为什么我的Android SQLite数据库有时无法加载数据库中的所有对象？

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