It looks to me like you're making the classic beginner mistake -- one that even bites experienced database programmers if we're at all inattentive...
Cursors start out positioned *before* the first row. You have to actually position them to the first row before you try to access data. c.moveToFirst() will position you there -- but check the return value; if it is false, you actually got an empty result, and there IS no first row. In other words, to access database data, you always have to position- and-check first. On Apr 15, 10:06 am, kc2uno_CMU <[email protected]> wrote: > Hi all, > > I just wrote my own DbAdapter by modifying the example DbAdapter in > Notepad tutorial. The problem came when I tried to fetch data from the > Database using my DbAdapter. I got : > "android.database.CursorIndexOutOfBoundsException: Index -1 requested, > with a size of 1." Below is a snippet of my code that I was trying to > play around with the DB: > > //rep,index are both some random integers that > I'm trying to store in a row > ex_rowId = mDbHelper.createExSet(rep, index, > 1); > if(D) Log.d(TAG, "rowid that was used for insertion: > " + ex_rowId); > > Cursor c = mDbHelper.fetchExRow(ex_rowId); > if(c == null) > Log.d(TAG, "HOLY-cursor null"); > //a cursor's lifecycle is automatically taken care of > startManagingCursor(c); > int repIndex = > c.getColumnIndex(BtDbAdapter.KEY_EX_REP); > if(D) > { > Log.d(TAG,"HOLY-column rep index: "+repIndex); > Log.d(TAG,"HOLY_column count: > "+c.getColumnCount()+ > "row count: "+c.getCount()); > } > int i=0; > for(;i<c.getColumnCount();i++) > { > Log.d(TAG,"Column names: > "+c.getColumnName(i).toString()); > } > > int repCount = c.getInt(repIndex); > if(D) Log.d(TAG, "HOLY-rep count: "+repCount); > > In summary, the code above first creates a new row, which stores some > values into a row. Then it fetches the same row by using the returned > row id. At last I am trying to retrieve the values from the cursor. > Below is the debug print log: > > 04-14 19:14:11.896: DEBUG/BluetoothChat(710): rowid that was used for > insertion: 3 > 04-14 19:14:11.906: DEBUG/BluetoothChat(710): HOLY-column rep index: 1 > 04-14 19:14:11.906: DEBUG/BluetoothChat(710): HOLY_column count: 4 row > count: 1 > > 04-14 19:14:11.906: DEBUG/BluetoothChat(710): Column names: _id > 04-14 19:14:11.916: DEBUG/BluetoothChat(710): Column names: repetition > 04-14 19:14:11.916: DEBUG/BluetoothChat(710): Column names: > ex_timestamp > 04-14 19:14:11.916: DEBUG/BluetoothChat(710): Column names: ex_unique > > 04-14 19:14:11.916: DEBUG/AndroidRuntime(710): Shutting down VM > 04-14 19:14:11.916: WARN/dalvikvm(710): threadid=3: thread exiting > with uncaught exception (group=0x4001da28) > 04-14 19:14:11.916: ERROR/AndroidRuntime(710): Uncaught handler: > thread main exiting due to uncaught exception > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): > android.database.CursorIndexOutOfBoundsException: Index -1 requested, > with a size of 1 > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > android.database.AbstractCursor.checkPosition(AbstractCursor.java:580) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > android.database.AbstractWindowedCursor.checkPosition(AbstractWindowedCurso > r.java: > 172) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > android.database.AbstractWindowedCursor.getInt(AbstractWindowedCursor.java: > 84) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > com.example.android.BluetoothChat.BluetoothChat > $1.handleMessage(BluetoothChat.java:325) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > android.os.Handler.dispatchMessage(Handler.java:99) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > android.os.Looper.loop(Looper.java:123) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > android.app.ActivityThread.main(ActivityThread.java:4203) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > java.lang.reflect.Method.invokeNative(Native Method) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > java.lang.reflect.Method.invoke(Method.java:521) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > com.android.internal.os.ZygoteInit > $MethodAndArgsCaller.run(ZygoteInit.java:791) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549) > 04-14 19:14:11.926: ERROR/AndroidRuntime(710): at > dalvik.system.NativeStart.main(Native Method) > 04-14 19:14:11.936: INFO/Process(76): Sending signal. PID: 710 SIG: 3 > 04-14 19:14:11.936: INFO/dalvikvm(710): threadid=7: reacting to signal > 3 > 04-14 19:14:11.966: INFO/dalvikvm(710): Wrote stack trace to '/data/ > anr/traces.txt' > 04-14 19:14:15.696: DEBUG/dalvikvm(370): GC freed 43 objects / 2112 > bytes in 94ms > 04-14 19:14:20.766: DEBUG/dalvikvm(150): GC freed 4543 objects / > 253432 bytes in 161ms > 04-14 19:14:24.676: INFO/Process(710): Sending signal. PID: 710 SIG: 9 > 04-14 19:14:24.706: ERROR/JavaBinder(76): !!! FAILED BINDER > TRANSACTION !!! > > As anyone can see, the row count is 1 !!!!! Therefore I am not exactly > sure what the bug is. Part of my DB code is also shown below: > > public static final String KEY_EX_ROWID = "_id"; > public static final String KEY_EX_REP = "repetition"; > public static final String KEY_EX_TIMESTAMP = "ex_timestamp"; > //this identifies the particular set of exercise the user was doing > public static final String KEY_EX_UNIQUE_ID = "ex_unique"; > > private static final String DATABASE_CREATE_EX = > "create table exsetTable (_id integer primary key > autoincrement, " > + "repetition integer not null, ex_timestamp integer not > null, ex_unique integer not null);"; > private static final String DATABASE_TABLE_EXSET = > "exsetTable"; > @Override > public void onCreate(SQLiteDatabase db) { > //create tables-exec can only take one query at a time. > Creating 2 different tables > > db.execSQL(DATABASE_CREATE_EX); > db.execSQL(DATABASE_CREATE_HR); > Log.d(TAG,"DB CREATION DONE"); > } > public long createExSet(int rep, int timestamp, int ex_uniqueId) { > ContentValues initialValues = new ContentValues(); > initialValues.put(KEY_EX_REP, rep); > initialValues.put(KEY_EX_TIMESTAMP, timestamp); > initialValues.put(KEY_EX_UNIQUE_ID, ex_uniqueId); > > return mDb.insert(DATABASE_TABLE_EXSET, null, initialValues); > } > public Cursor fetchExRow(long ex_rowId) { > Cursor mCursor = mDb.query(DATABASE_TABLE_EXSET, > new String[] > {KEY_EX_ROWID,KEY_EX_REP,KEY_EX_TIMESTAMP,KEY_EX_UNIQUE_ID}, > KEY_EX_ROWID + "=" + ex_rowId, null, null, null, > null); > return mCursor; > } > > I am not sure if the cursor returned from fetchExRow is valid. Would > it still give me row count 1 if it's invalid(empty)? The bug is either > in the way I am trying to retrieve data using getInt or my > databaseadapter's code. Is there a way to view the databases and > tables I created using some tools? > Thank you so much! -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/android-developers?hl=en To unsubscribe, reply using "remove me" as the subject.
