I've started implementing a UIScrollView that will contain many thumbnail-sized pictures and will scroll only horizontally. For this, I keep a limited number of UIImageViews created and remove/add them to the UIScrollView as the user scrolls it.
The problem is I need to find a way to optimize it as scrolling sometimes gets sluggish. Maybe it's the adding/removing from the view, I don't know.
I figure this is a common component that might have been implemented more than once, but I couldn't find any library that featured something like this. If there is something ready available, I wouldn't need to spend many hours fine tuning or figuring out how to improve my component.
This is different from the question that has been asked here many times: I don't want it to behave like the photos app. I want many pictures to be visible at a time and to scroll them smoothly, without "hard pages".
So, anyone know of a component which does something similar to this?
I managed to do something similar by using a rotated UITableView instead:
UITableView *tableView = [[UITableView alloc] initWithFrame:...];
tableView.transform = CGAffineTransformMakeRotation( -M_PI/2 );
You can then configure your UITableViewCells to display the images. You can also rotate the UITableViewCell contentsView.
I made a two dimensional scrolling component called DTGridView. You can use it with just the one row to make a purely horizontal scroll view. It has an API much like UITableView, where you have a dataSource and a delegate to tell it how many rows/columns etc and to handle touch events for the cells.
It also uses a method of cell reuse like UITableView does to save on memory. If you aren't using cell reuse on table views, you should be. :)
Related
in my app I have a uiview with a tableview inside of it. This tableview consists of only one cell which is rather high (ca. 750) and contains alot of objects (uitextfields, uitextview, images, buttons, uiscrollview, smaller uitableview, etc).
I'm experiencing a small stuttering when scrolling the tableviewcell which I can't seem to get rid of.
Is it the large amounts of objects in one cell or should I distribute the objects into multiple cells to get rid of the stuttering?
Would be great if somebody has experienced the same issue and could help me out here a little.
Thanks a lot!
I tried this trick with tableHeaderView - works perfect for me! I'm also have a large hierarchy of subviews. ALso if you need some easy custom UI elements appearance/disappearance animations you can divide it into different cells. I love doing like that because of UITextViews and UITextFields - UITableViewController makes layout for keyboard appearance automatically.
So I have a UITableViewController. The cells in this tableview have the following UIControls:
2 UILabels, one of which has a shadow and a clearColor background color.
1 Custom Progress view resized to be larger and with a different color
3 UIButtons
Functionally, they do exactly what they are supposed to do. However, I've noticed when looking at it on device that scrolling performance quickly tanks and has dropped frames all over the place, even with other interactions like pushing one of the buttons.
So I was reading around today and found http://blog.atebits.com/2008/12/fast-scrolling-in-tweetie-with-uitableview/ this article by the Tweetie guy about how to achieve fast scrolling performance by subclassing UITableViewCell and doing the drawing yourself.
The example works extremely well, but when I tried to adapt it to work with my desired configuration I realized that he isn't using any predefined UI Controls, he's mapping out everything by hand.
While I can see how this would be an extremely efficient way to do things, it strikes me as problematic for things like the progress view and the buttons, and even one of my labels to a certain extent.
So my question is this: Do I need to completely write my controls from scratch if I want my scrolling performance to be good, or is there a way to use the standard UI Controls and get good scrolling performance?
If you're adding custom controls to your cell, you should still be subclassing UITableViewCell, adding your controls in the init function, laying them out in layoutSubviews, etc. - just like any other view. As VdesmedT says, make sure you're re-using cells via the dequeue mechanism, so that you aren't allocating new cells with each scrolling operation.
OK, I will propose something obvious but to achieve UIScrollView performance, you need to be sure that the dequeue mechanism works well. I often see developers not properly set the identifier in IB and therefore missing the UITableViewCell cache benefit
I am trying to create a excel like view in my app. To do that I wanted to achieve both horizontal n vertical swipes at the same time .i.e., if the vertical scroll would fill with rows and the horizontal with columns.. have no clue hw to begin with.
This is an interesting question. For sure I would say start with UIScrollView, and set the content size bigger than the screen size, exactly how big is up to you.
Next you'll want to make some kind of implementation that efficiently figures out what cells are on screen. If I were you I would do something similar to how UITableView is done, i.e. make a custom object that keeps track of what indexes should be on screen based on the offset of the scroll view.
Next you'll need this custom object to either directly or indirectly get the visible cells to display themselves on screen when they are visible, and remove them from the superview when they aren't. I'd also recommend reusing the views that are offscreen.
This is a moderately challenging thing you are trying to make, so be sure you are very organized and don't be scared to make a few new custom object to perform specific tasks.
Sample interface file:
#protocol doubleTableViewDelegate
-(NSInteger)heightForRow:(NSInteger)row;
-(NSInteger)widthForCol:(NSInteger)col;
-(NSInteger)numberOfRows:(NSInteger)rows;
-(NSInteger)numberOfCols:(NSInteger)cols;
-(UIView *)cellForRow:(NSInteger)row col:(NSInteger)col; //get the custom table view to store and dequeue these, i.e. store them in an NSSet when they go offscreen, and give them back when a certain function is called.
//There's probably a few functions missing here still.
#end
#interface doubleTableView: UIScrollView {
id<doubleTableViewDelegate> infoDelegate;
}
//your functions to show and remove cells as needed
#end
You'll need to work out the rest, but keep updating this page and I'll try to help out.
Good luck with this, let me know how it goes.
I have a UIScrollView that I am using to simulate a UITableView like interaction because rows are a bit more complex than what UITableView has to offer. I have 4 UILables a UIImageView and a UIButton for every row. The end result is a lot of subviews.
Even with only 10 rows,the scroll view that looks fine in the simulator but has a fairly low frame rate on the iPhone 4. This is a resource consumption issue for sure.
Is there a way to optimize the redraw durring scrolling like double buffering?
If not is there another way to get customizable UITableview functionality?
thanks
Does every View have 4xUILabels, a UIImageView and a UIButton?
I would create a nib file with a custom UITableViewCell (You can make those as complex as you want), then you can reuse the cells to help with your performance.
Information on how to do this is here:
http://developer.apple.com/iphone/library/documentation/UserExperience/Conceptual/TableView_iPhone/TableViewCells/TableViewCells.html#//apple_ref/doc/uid/TP40007451-CH7-SW1
I think you probably want to create a custom subclass of a UITableViewCell as the UITableView will handle all the redrawing for you. In a custom UITableViewCell you can add as many subviews as you like.
Take a look at http://cocoawithlove.com/2009/04/easy-custom-uitableview-drawing.html.
UITableViews are subclasses of UIScrollView (or at least conform to their behavior), but you really want to let the iPhone handle the selective drawing/cell reuse for you that the UITableView provides.
You should use UITableView if it does everything you need.
However if your tableview cells are really complicated, or you want to enable paging on the scrollview, you should take a look at the PageContol sample code that Apple provides. In a nutshell, you watch for movement in scrollViewDidScroll: and load new "pages" just before they become visible. This method works very well in practice for arbitrarily long lists of pages.
I'm thinking about how I could achieve this kind of UITableView: http://snapplr.com/c1x5
So it has multiple (separately selectable) columns in it which also differ in width. Apart from that it can also scroll sideways to see programs which broadcast later on the day.
Now, I'd like to know how you would implement this kind of feature. A scrollview wouldn't be enough, it has to somehow load newer data. And of course you need to be able to know what column in the cell has been selected.
Hope to hear some thoughts.
That is a custom view.
It's possible it could be a table view, with heavily customised cells, but that would have been a hell of a lot of work to get it scroll horizontally too.
It's more likely that it's a scroll view with a custom grid view type class that have support for arbitrary grid cell widths...
I'm sure if you write something like this you'll have a lot of interested people.
I just updated MDSpreadView, which is basically a UITableView that works both horizontally and vertically, floating headers and all, with an API very similar to UITableView.