TableView:getRowAtIndex returns nil on valid rows

IronMan · January 17, 2015, 4:48pm

@Rob, I try to wait 5-10sec but still error. I use print command to get this…

I insert 3 row, and I delete first one, then I get this. but if I delete the last one is ok, same problem when I delete the second row.

Jan 17 23:41:56.272: Start Insert to Terpilih Table View

Jan 17 23:41:56.272: Row Index Peserta : 1

Jan 17 23:41:56.272: ID Peserta : 218

Jan 17 23:41:56.273: Number of Rows : 1

Jan 17 23:41:56.273: End Insert to Terpilih Table View

Jan 17 23:41:57.211: Start Insert to Terpilih Table View

Jan 17 23:41:57.212: Row Index Peserta : 2

Jan 17 23:41:57.212: ID Peserta : 176

Jan 17 23:41:57.212: Number of Rows : 2

Jan 17 23:41:57.212: End Insert to Terpilih Table View

Jan 17 23:41:58.713: Start Insert to Terpilih Table View

Jan 17 23:41:58.713: Row Index Peserta : 3

Jan 17 23:41:58.713: ID Peserta : 115

Jan 17 23:41:58.713: Number of Rows : 3

Jan 17 23:41:58.714: End Insert to Terpilih Table View

Jan 17 23:42:01.926: Start Touch Delete Terpilih Row

Jan 17 23:42:01.927: Row Index : 1

Jan 17 23:42:01.927: Target Index : 1

Jan 17 23:42:01.927: Number of Before Delete Row : 3

Jan 17 23:42:01.927: Number of Before Delete Row : 2

Jan 17 23:42:01.927: End Touch Delete Terpilih Row

Note use object:getRowAtIndex()

Jan 17 23:42:05.769: Note : Nil. Row at index 1 shouldn’t be nil. Total Rows = 2

Jan 17 23:42:05.769: Start Print Data from Terpilih Table

Jan 17 23:42:05.770: [null,176]

Jan 17 23:42:05.770: End Print Data from Terpilih Table

rob · January 17, 2015, 5:34pm

Can you explain why you are doing this? Can you post the actual code involved? We probably don’t need to see whole thing, just the code involved with rendering/creating/deleteing table entries, etc.

What version of Corona SDK are you using?

Rob

IronMan · January 17, 2015, 5:58pm

this is the code…

local function renderTerpilihRow( event ) local phase = event.phase local row = event.row local params = event.row.params row.User = display.newText( row, params.name, 0, 0, "Helvetica Neue", 18 ) row.User:setFillColor( 1, 1, 1 ) row.User.anchorX = 0 row.User.x = 15 row.User.y = row.contentHeight / 5 row.ID = params.id end local function touchTerpilihRow( event ) local phase = event.phase local row = event.target if "release" == phase then terpilihLists:deleteRow( row.index ) end end -- Code execute when submit button clicked local terpilihTable = {} local totalRows = terpilihLists:getNumRows() for tp = 1, totalRows do if ( terpilihLists:getRowAtIndex( tp ) == nil ) then print( "Note : Null. Row at index " .. tp .. " shouldn't be null. Total Rows = " .. totalRows ) else terpilihTable[tp] = tonumber(terpilihLists:getRowAtIndex( tp ).ID) end end

IronMan · January 16, 2015, 4:52pm

I have that problem to, is that a bug or what?

rob · January 17, 2015, 2:19am

@IronMan, if the tableView can display 10 total rows and your app has 20 total rows, then 10 of them are on screen, 10 of them are off screen. If rows 1-10 are on screen, then tableView:getRowAtIndex( i ) will return nil for rows 11-20.

Rob

corona273 · January 17, 2015, 5:53am

FYI in my experience the TableView widget will render one or two rows offscreen so they’re ready immediately during a fast scroll event. I haven’t ever measured exactly how many, but I’m pretty sure I’m right.

Otherwise tableView:getRowAtIndex() works as Rob describes.

IronMan · January 17, 2015, 2:24pm

@Rob, but if I delete the first row and call obj:getRowAtIndex() I get error cause data is nil, but if I delete the last row it’s fine.

so I use print to getNumRow of that table, and the reulst is different from the row that in the table. but if I delete one more then getNumRow get update.

IronMan · January 17, 2015, 2:38pm

but, I get idea to fix this problem now. but error for nil when row delete then getRowAtIndex() I think is a bug.

rob · January 17, 2015, 3:31pm

Are you saying that:

tableView:deleteRow(1)

tableView:getRowAtIndex(1)

is returning nil when the new row 1 should now be the previous row 2?

Rob

IronMan · January 17, 2015, 3:34pm

yes, is that a bug or should I use different approach?

corona273 · January 17, 2015, 4:31pm

<IronMan>: You should reference this topic re: deletion timing: http://forums.coronalabs.com/topic/47558-tableview-20-delete-a-row-without-animation/

rob · January 17, 2015, 4:34pm

Its likely because the code executes so fast, that it could be trying to reference the row right after it’s deleted but before the table has been re-indexed. As @corona273 mentions, there are animations going on when deleting the row. There could also be a micro timer in there that could give the row deletion a little async property and it purely could be a race condition. Try dropping your get index call into a timer with say a 500ms delay and see if that changes the behavior.

IronMan · January 17, 2015, 4:48pm