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How to stop UITableView moveRowAtIndexPath from leaving blank rows upon reordering

Answer 1

A:

SO... Actually problem is in Three20 framework. TTTableView, which is subclass of UITableView have two buggy methods:

///////////////////////////////////////////////////////////////////////////////////////////////////
// UIScrollView

- (void)setContentSize:(CGSize)size {
  if (_contentOrigin) {
    CGFloat minHeight = self.height + _contentOrigin;
    if (size.height < minHeight) {
      size.height = self.height + _contentOrigin;
    }
  }

  CGFloat y = self.contentOffset.y;
  [super setContentSize:size];

  if (_contentOrigin) {
    // As described below in setContentOffset, UITableView insists on messing with the 
    // content offset sometimes when you change the content size or the height of the table
    self.contentOffset = CGPointMake(0, y);
  }
}

- (void)setContentOffset:(CGPoint)point {
  // UITableView (and UIScrollView) are really stupid about resetting the content offset
  // when the table view itself is resized.  There are times when I scroll to a point and then
  // disable scrolling, and I don't want the table view scrolling somewhere else just because
  // it was resized.  
  if (self.scrollEnabled) {
    if (!(_contentOrigin && self.contentOffset.y == _contentOrigin && point.y == 0)) {
      [super setContentOffset:point];
    }
  }
}

Just comment them, And all will works fine. I don't know if this will destroy something somewhere, but at least, you know where the problem is.

tt.Kilew 2010-02-13 04:16:25

Thanks! I have actually isolated it even further with your guidance. The problem is that when reordering the row, self.scrollEnabled is NO so the super line is not called. I am going to have to look into why this was done (I'm sure it had a reason) but it might be so obscure that I can change it back.

coneybeare 2010-02-13 04:25:59

Answer 2

A:

Cross-posting my answer to this related question:

I just hit what I believe is the same problem in my app.

The situation is that I have two table sections. Items can be dragged within and between sections. Users can drag cells to any row in the first section, but in the second section the items are sorted, so for any given cell, there's only one valid row.

If I scroll the view so that the bottom of section 1 and the top of section 2 are visible, grab an item in section 1 that sorts to the bottom of section 2, and drag it into the the top of section 2, my tableView:targetIndexPathForMoveFromRowAtIndexPath:toProposedIndexPath: method gets called and I return the correct destination position, which is several rows below the bottom of the screen. In the UI, you can see an empty cell gets created at the bottom of the screen, which is not the correct destination row.

When you let go of the cell, that bogus cell that was created at the bottom of the screen (in the middle of section 2) stays there! tableView:cellForRowAtIndexPath: never even gets called for it. As soon as you try to do anything with that cell, you crash.

My first solution was to just call [tableView reloadData] at the end of tableView:moveRowAtIndexPath:toIndexPath:. But that causes a crash, so instead I call it indirectly after a delay. But then there's another bug: after the delayed reloadData call, tableView:moveRowAtIndexPath:toIndexPath: gets called again with a bogus request to move an item one past the end of the first section to that same position. So, I had to add code to ignore bogus no-op requests.

So, here's the code:

- (void)tableView:(UITableView *)tableView moveRowAtIndexPath:(NSIndexPath *)pathSrc toIndexPath:(NSIndexPath *)pathDst
{
  // APPLE_BUG: after doing the delayed table reload (see below), we get a bogus
  // request to move a nonexistant cell to its current location
  if (pathSrc.row == pathDst.row && pathSrc.section == pathDst.section)
    return;

  // update your data model to reflect the move...

  // APPLE_BUG: if you move a cell to a row that's off-screen (because the destination
  // has been modified), the bogus cell gets created and eventually will cause a crash
  [self performSelector:@selector(delayedReloadData:) withObject:tableView afterDelay:0];
}

- (void)delayedReloadData:(UITableView *)tableView
{
  Assert(tableView == self.tableView);
  [tableView reloadData];
}

Note that there's still a UI bug. On the screen, the dragged cell gets animated into the bogus empty cell. At the end of the animation, the empty cell gets redrawn with the correct data for that row, but the observant user will notice the dragged cell getting animated to the wrong spot then instantly morphed to a different cell.

This is definitely a goofy UI. I considered scrolling the proper destination row onto the screen, but if I were to do that it would fill the screen with section two and then any attempt to drag back to section one would be continually thwarted by my (now annoying) autoscrolling. I may have to change the UI, but that would require some complex and bothersome changes to my data model.

Tom Saxton 2010-04-26 17:08:58

Answer 3

A:

Hallo Tom!

You actually solved my problem! For detailed information see: http://stackoverflow.com/questions/3014906/reranging-a-uitableview

Thank you very much!

Nicolay 2010-06-11 07:47:47

Answer 4

A:

removed my answer, didn't work after all

Rene 2010-08-03 12:09:22

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How to stop UITableView moveRowAtIndexPath from leaving blank rows upon reordering

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