StackOverflow2013

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copied!<p>Here you go. A proof of concept of a speed enhancer of the scroll when you move a cell, SDK 3.1. It may not pass Apple's requirements since overriding _beginReorderingForCell and _endReorderingForCell looks a little off-spec. There are other ways to determine if a cell starts or ends reordering (e.g. subclassing <code>UITableViewCell</code> and finding some measure) but this is the easiest I think.</p> <p>The approach is quite simple: for every movement of Y pixels down, we move 2*Y pixels down, only when reordering.</p> <p>The problem is that the currently dragged cell is a subview of the table view, so it shifts with the table view if we move it. If we are to correct for that within this <code>setContentOffset</code>, it has no effect since the position of the cell will be set based on values calculated apart from the current <code>contentOffset</code>. Therefore we correct an instant later using <code>performSelector</code>.</p> <p>I left the debugging lines in there for convenience. All you need to do is to use <code>FastUITableView</code> instead of <code>UITableView</code> (esp. in you NIB)</p> <p>You may of course want to add some timing things, so that the speed only goes up after 1 second or so. That will be trivial.</p> <pre><code>@interface FastUITableView : UITableView { UITableViewCell *draggingCell; CGFloat lastY; } @end @implementation FastUITableView -(void)_beginReorderingForCell:(UITableViewCell*)cell { printf("begin reordering for cell %x\n",cell); draggingCell = cell; lastY = -1.0f; [super _beginReorderingForCell:cell]; } -(void)_endReorderingForCell:(UITableViewCell*)cell wasCancelled:(BOOL)cancelled animated:(BOOL)animated { printf("end reordering for cell %x\n",cell); draggingCell = nil; [super _endReorderingForCell:cell wasCancelled:cancelled animated:animated]; } -(void)setContentOffset:(CGPoint)pt { if ( !draggingCell ) { [super setContentOffset:pt]; return; } if ( lastY < 0 ) lastY = pt.y; CGPoint fast = pt; float diff = pt.y - lastY; //diff *= 0.5; /// <<--- control speed here fast.y = pt.y + diff; if ( fast.y > self.contentSize.height - self.superview.frame.size.height ) { CGFloat corr = fast.y - self.contentSize.height + self.superview.frame.size.height; printf("Correction: %f\n",corr); fast.y -= corr; diff -= corr; } else if ( fast.y < 0.0f ) { CGFloat corr = -fast.y; printf("Correction: %f\n",corr); diff += corr; fast.y += corr; } [self performSelector:@selector(moveCell:) withObject:[NSNumber numberWithFloat:diff] afterDelay:0.01]; lastY = fast.y; // printf("setting content offset: %f -> %f of max %f\n",pt.y, fast.y, self.contentSize.height); [super setContentOffset:fast]; } -(void)moveCell:(NSNumber*)diff { CGRect frame = draggingCell.frame; frame.origin.y += [diff floatValue]; // printf("shifting cell %x with %f\n",draggingCell,[diff floatValue]); draggingCell.frame = frame; } </code></pre>

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