UITableView: scrolling programmatically the content view - iphone

Question

Hi i'm trying to forward the touches I receive from an UIView which is in front of an UITableView. But doins so I can't make the table scroll anymore (see here).
So now I'm trying to make tha tableview scroll programmatically and I am looking at setContentOffset:animated: and scrollRectToVisible:animated: with having success only with the first.
Here is my code in a class that subclasses the UITableView:
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{
NSLog(#"BEGTB");
//previousXPan = 0.0;
UITouch * touch = [touches anyObject];
CGPoint tPoint = [touch locationInView:self];
previousYPan = tPoint.y;
[super touchesBegan:touches withEvent:event];
//
//[super touchesShouldBegin:touches withEvent:event inContentView:self];
//[[self nextResponder] touchesBegan:touches withEvent:event];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch * touch = [touches anyObject];
CGPoint tPoint = [touch locationInView:self];
NSLog(#"MOVTB");
NSLog(#"BOUNDZ %f, %f, %f, %f", self.bounds.origin.x, self.bounds.origin.y, self.bounds.size.height, self.bounds.size.width);
NSLog(#"CONTENT SIZE %f, %f", self.contentSize.height, self.contentSize.width);
CGRect rc = [self bounds];
NSLog(#"%f %f", rc.size.height, rc.size.width);
CGRect newRect = CGRectMake(rc.origin.x, rc.origin.y + self.contentSize.height, self.contentSize.width, fabs(tPoint.y - previousYPan));
NSLog(#"BOND RECT %f, %f, %f, %f", rc.origin.x, rc.origin.y, rc.size.height, rc.size.width);
NSLog(#"NEW RECT %f, %f, %f, %f", newRect.origin.x, newRect.origin.y, newRect.size.height, newRect.size.width);
//[self scrollRectToVisible:newRect animated:YES];
NSLog(#"Content OFFSET %f",tPoint.y - previousYPan);
[self setContentOffset:CGPointMake(rc.origin.x,(tPoint.y - previousYPan) *2.0 )animated:YES];
previousYPan = tPoint.y;
//[super touchesMoved:touches withEvent:event];
//[[self nextResponder] touchesMoved:touches withEvent:event];
}
But the result is really laggy and buggy. Any better idea?

Answer 1

I almost found a suitable solution (it is not like a normal scrolling but...).
First I determine the mamimum and minimum amount of pixels in the content area of the table view on the Y axis ( the height of the contentSize when the view has been fully loaded).
The I check the movement done incrementally but not referencing the position of the touch in the table view! I have to check it on a top layered UIView that covers it, because when you alter the content offset of the table you change dynamically its dimensions and you can end you having an acceleration effect .
Here is some code:
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event{
UITouch * touch = [touches anyObject];
CGPoint tPoint = [touch locationInView:[viewController draggableAreaView]];
CGRect rc = [self bounds];
float totalOS = tPoint.y - previousYPan;
if ((contentOffSetY >= minY && contentOffSetY <= maxY) ||
(contentOffSetY < minY - 5 && totalOS < 0) ||
(contentOffSetY > maxY + 5 && totalOS > 0))
{
if (totalOS > 0)
totalOS += OFFSET;
else if (totalOS < 0)
totalOS -= OFFSET;
[self setContentOffset:CGPointMake(rc.origin.x,self.contentOffset.y + totalOS)animated:NO];
}
else /*if (contentOffSetY < minY - 5 && totalOS < 0) */
{
[self resetOffset];
}
previousYPan = tPoint.y;
}
- (void)resetOffset{
CGRect rc = [self bounds];
if(contentOffSetY < minY)
{
[self setContentOffset:CGPointMake(rc.origin.x, minY + 50)animated:YES];
}
else if (contentOffSetY > maxY)
{
[self setContentOffset:CGPointMake(rc.origin.x, maxY - 50)animated:YES];
}
}
Some more tips:
here draggableAreaView is the top UIView from which I get an "absolute" position
OFFSET is a constant defined to increment linearly the speed of the scroolling (without it the touchesMoved: , called many times, gives a relative movement of just one pixel each time)
,minY and maxY are the precalculated limit values (in order to compute them I calculated the height of all the cells in the table for max and the height of the visible content view for min)
I added some displacement to minY and maxY in order to have a more visible animation