UITableView headers on the left side of sections (like Spotlight)

Been searching for this for quite a while, and I still haven't found a way to do it. I'd like to reproduce the section headers of the iPhone's Spotlight into a UITableView.

"Regular" table view headers sta开发者_如何学JAVAy visible at the top of a section when you scroll, as we all know. But there is one kind of header that I've never seen elsewhere than in the Spotlight page of Springboard: there, the headers span the whole height of the section and are not stuck on the top of the section, but on the left side.

How the heck is that achieved?

Good question. I made a little experiment. It almost looks like the view from spotlight. But it's lacking one import feature. The lower "image" doesn't push the upper image to the top if they collide.

I doubt that there is a built in solution without the use of private frameworks.

I achieved this:

As you can see the two header images at the top overlap. They don't push each other like normal headers to. And I had to deactivate the cell separators. If I would use them they would appear at the whole cell. So you have to draw them yourself. Not a big deal.

But I have no idea how I could fix the overlapping.

Here is the code that made this happen:

- (CGFloat)tableView:(UITableView *)tableView heightForHeaderInSection:(NSInteger)section {
    return 1;
}

- (UIView *)tableView:(UITableView *)tableView viewForHeaderInSection:(NSInteger)section {
    UIView *contentView = [[UIView alloc] initWithFrame:CGRectMake(0, 0, self.tableView.bounds.size.width, 44)];
    contentView.backgroundColor = [UIColor lightGrayColor];

    UIImageView *imageView = [[[UIImageView alloc] initWithFrame:CGRectMake(5, 5, 34, 34)] autorelease];
    imageView.image = [UIImage imageNamed:[NSString stringWithFormat:@"%d", section]];;

    [contentView addSubview:imageView];
    return [contentView autorelease];
}

Okay I have done something similar to what the music app and spotlight search does.

I have not subclassed UITableView, I have just tracked the sections through it's scrollViewDidScroll method, and added the header views to the left of the tableView (so you will have to put the tableview to the right in your viewController's view, which means you can't use UITableViewController).

this method should be called in the scrollViewDidScroll, ViewDidLoad, and in didRotateFromInterfaceOrientation: (if you support rotation)

keep in mind that you will have to make space in the left equal to the size of the headers in any interface orientation that you support.

-(void)updateHeadersLocation
{
for (int sectionNumber = 0; sectionNumber != [self numberOfSectionsInTableView:self.tableView]; sectionNumber++)
{
    // get the rect of the section from the tableview, and convert it to it's superview's coordinates
    CGRect rect = [self.tableView convertRect:[self.tableView rectForSection:sectionNumber] toView:[self.tableView superview]];

    // get the intersection between the section's rect and the view's rect, this will help in knowing what portion of the section is showing
    CGRect intersection = CGRectIntersection(rect, self.tableView.frame);

    CGRect viewFrame = CGRectZero; // we will start off with zero

    viewFrame.size = [self headerSize]; // let's set the size

    viewFrame.origin.x = [self headerXOrigin];

    /*

     three cases:

     1. the section's origin is still showing -> header view will follow the origin
     2. the section's origin isn't showing but some part of the section still shows -> header view will stick to the top
     3. the part of the section that's showing is not sufficient for the view's height -> will move the header view up

     */

    if (rect.origin.y >= self.tableView.frame.origin.y)
    {
        // case 1
        viewFrame.origin.y = rect.origin.y;
    }
    else
    {
        if (intersection.size.height >= viewFrame.size.height)
        {
            // case 2
            viewFrame.origin.y = self.tableView.frame.origin.y;
        }
        else
        {
            // case 3
            viewFrame.origin.y = self.tableView.frame.origin.y + intersection.size.height - viewFrame.size.height;
        }
    }

    UIView* view = [self.headerViewsDictionary objectForKey:[NSString stringWithFormat:@"%i", sectionNumber]];

    // check if the header view is needed
    if (intersection.size.height == 0)
    {
        // not needed, remove it
        if (view)
        {
            [view removeFromSuperview];
            [self.headerViewsDictionary removeObjectForKey:[NSString stringWithFormat:@"%i", sectionNumber]];
            view = nil;
        }
    }
    else if(!view)
    {
        // needed, but not available, create it and add it as a subview

        view = [self headerViewForSection:sectionNumber];

        if (!self.headerViewsDictionary && view)
            self.headerViewsDictionary = [NSMutableDictionary dictionary];

        if (view)
        {
            [self.headerViewsDictionary setValue:view forKey:[NSString stringWithFormat:@"%i", sectionNumber]];

            [self.view addSubview:view];
        }
    }


    [view setFrame:viewFrame];
}
}

also we need to declare a property that would keep the views that are visible:

@property (nonatomic, strong) NSMutableDictionary* headerViewsDictionary;

these methods return the size and X axis offset of the header views:

-(CGSize)headerSize
{
return CGSizeMake(44.0f, 44.0f);
}

-(CGFloat)headerXOrigin
{
return 10.0f;
} 

I have Built the code so that any header view that's not needed gets removed, so we need a method that would return the view whenever needed:

-(UIView*)headerViewForSection:(NSInteger)index
{
UIImageView* view = [[UIImageView alloc] init];

if (index % 2)
{
    [view setImage:[UIImage imageNamed:@"call"]];
}
else
{
    [view setImage:[UIImage imageNamed:@"mail"]];
}

return view;
}

here's how it will look :

How it will look in lanscape, I have used contraints to give 44px in the left of the tableView

Good news: See answer of How to achieve an advanced table view header

result http://i.minus.com/jyea3I5qbUdoQ.png