iOS: Stretching / Resizing UITableView Header As T

问题:

Using storyboard, I have placed an imageView as my tableView's headerView inside a ViewController.

This is how my storyboard is set up:

Depending on what data the user is viewing, the viewController will either show or hide the headerView. My question is, that when the headerView is visible and the user drags down on the tableView, how can I have the imageView stick to both the navigationBar and the tableView as it resizes to cover the space in between?

This is what it currently does:

But this is what I'm going for:

Any help would be greatly appreciated. I've looked at parallax libraries, but none support sectionTitles, and I'm not necessarily going for the parallax effect either. When the user scrolls up, I want it to bounce back to the regularView and not hide the headerView. Thanks!

UPDATE:

I have followed the advice posted by Dany below and have done the following:

-(void)scrollViewDidScroll:(UIScrollView*)scrollView {

CGRect initialFrame = CGRectMake(0, 0, 320, 160);

if (scrollView.contentOffset.y < 0) {

    initialFrame.size.height =! scrollView.contentOffset.y;
    childHeaderView.frame = initialFrame;
} }

childHeaderView is an imageView and for some reason when I drag down, the image moves up (like half of it behind the navBar) and doesn't return. Any advice would be greatly appreciated!! Thanks!

回答1:

I recently posted a blog post about accomplishing this using constraints which might help, turns out it was quite straight forward.

Here is the link: Creating parallax effect on UIScrollView using constraints

回答2:

First of all you should remove the UIImageView from the header and add it as a simple UIImageView on top of the UITableView then since UITableViewDelegate protocol conforms to UIScrollViewDelegate protocol you can implement the scrollViewDidScroll: method to check when the tableView is scrolling down and has a bouncing effect. something like this:

-(void)someInitMethod {
   initialFrame = yourHeaderView.frame;
}
-(void)scrollViewDidScroll:(UIScrollView*)scrollView {
    if(scrollView.contentOffset.y < 0) {
       initialFrame.size.height -= scrollView.contentOffset.y;
       yourHeaderView.frame = initialFrame;
    }
}

Also make sure you set the proper contentMode for your UIImageView. Also I think this implementation will create a bouncing effect but I'm not sure because I can't test it right now but I think this is a good start point for you.

回答3:

This is how I achieved it, in my case I was using a map view up the top:

1. Create a View Controller in storyboard.
2. Add a Table View and set the constraints to 0 from all sides.
3. Add a Map View (or whatever view) below the Table View so that it will get rendered over the top. It will look like it is overlapping.
4. Add constraints to the top left and right.
5. In the view controller viewDidLoad add the following: tableView.contentInset = UIEdgeInsetsMake(200, 0, 0, 0) where 200 is the height of the View. This will push the contents of the table view downwards.

6. In the view controller add the following code, which resizes the view based on the scrolling:

   func scrollViewDidScroll(scrollView: UIScrollView) {
       var scrollOffset = scrollView.contentOffset.y
       var headerFrame = mapView.frame
       if (scrollOffset < 0) {
           // Adjust map
           headerFrame = CGRect(x: mapView.frame.origin.x,
               y: mapView.frame.origin.y,
               width: mapView.frame.size.width,
               height: -scrollOffset)
       } else {
           // Adjust map
           headerFrame = CGRect(x: mapView.frame.origin.x,
               y: mapView.frame.origin.y,
               width: mapView.frame.size.width,
               height: 0)
       }
       mapView.frame = headerFrame
   }
   

If I could set contentInset from the storyboard it would be even more pretty

回答4:

Please have a look at this https://github.com/matteogobbi/MGSpotyViewController which implements the same effect as per your requirement.

回答5:

The earlier solutions on this page gave me some trouble when I needed this to work along with section titles and index bar, so I came up with the following alternative myself. Please note; I don't use autolayout in my project and I've only tested this on iOS9+;

In your project's storyboard:

1. Create a UITableView within a UIViewController (or try it with a UITableViewController).
2. Drop a UIView at the top (but within) the UITableView, so it becomes a table header above the first cell.
3. Give this header view a desired height (like 200px for example) and set the background color to "Clear Color". The Clear Color is important, the view needs to be see-through.
4. Drop a 2nd UIView within the table header UIView and make it the same size as it's parent. This will be the actual header, so feel free to give it any color, setup an image view or other content.
5. Connect this 2nd UIView to your UIViewController IBOutlet, I named it "headerView" in my case.

Next, go to your UIViewController.m:

- (void)viewDidLoad
{
    [super viewDidLoad];

    // Remove view from table header and place it in the background instead.
    [self.headerView removeFromSuperview];
    UIView *backgroundView = [UIView new];
    [backgroundView addSubview:self.headerView];
    self.tableView.backgroundView = backgroundView;
}

- (void)viewDidAppear:(BOOL)animated
{
    [super viewDidAppear:animated];

    /* Set initialScrollOffset ivar to start offset, because in my case
       the scroll offset was affected by the statusbar + navigation bar heights
       and the view controller's "extend edges under top bars" option. */
    initialScrollOffset = self.tableView.contentOffset.y;
}

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    /* Modify headerView height only if the table content gets pulled
       beyond initial offset. */
    if (scrollView.contentOffset.y < initialScrollOffset) {
        CGRect frame = self.headerView.frame;
        frame.size.height = self.tableView.tableHeaderView.frame.size.height + -scrollView.contentOffset.y;
        self.headerView.frame = frame;
    }
}

I needed this implementation only for a stretching header with background color and labels. It should be easy to add a UIImageView to this header though.

Also, steps 1 to 5 are completely optional of course. You can programmatically create your header view or use a XIB instead. As long as you make sure the table has a Clear Colored header view set with the same height as your desired header because this serves as a spacer to keep your cells and section titles in line.

EDIT:

I found an even cleaner way to accomplish this;

1. Build up your table header in interface builder as described above: 1 UIView as container with a 2nd UIView embedded within.
2. Skip the viewDidLoad code above, there is no need to pull the UIView out of it's container and we won't need to set it as a table background.
3. Change the scrollViewDidScroll: method to this:

UIViewController.m:

- (void)scrollViewDidScroll:(UIScrollView *)scrollView
{
      if (scrollView.contentOffset.y < initialScrollOffset) {
           CGRect frame = self.headerView.frame;
           frame.size.height = self.tableView.tableHeaderView.frame.size.height - scrollView.contentOffset.y;
           frame.origin.y = self.tableView.tableHeaderView.frame.origin.y + scrollView.contentOffset.y;
           self.headerView.frame = frame;
    }
}

That's it. Only visual difference from the other solution is that the contents will now scroll up along with the rest of the cells instead of being overlapped by them.

回答6:

I don't know, if this would help you or not ..

Set your scroll delegate to self.

and then implement this:

-(void)scrollViewDidScroll:(UIScrollView *)scrollView
{
    float scrollViewHeight = scrollView.frame.size.height;
    float scrollContentSizeHeight = scrollView.contentSize.height;
    float scrollOffset = scrollView.contentOffset.y;

    if (scrollOffset == 0)
    {
        // then we are at the top
    }
    else if (scrollOffset + scrollViewHeight == scrollContentSizeHeight)
    {
        // then we are at the end
        // Do what you need here 
    }
}