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.
Related
I need to create a screen that scrolls vertically - like the tableview but I need 3 columns and within those 3 columns I need to add images of varying height - so this will not fit into rows that a tableview can provide.
Should I create 3 tableviews and lay them out side by side - or something else. I think I could build this by simply positioning the images using coordinates but I wanted to benefit from methods that the table view can provide.
If you want the columns to act stuck together, so that they all scroll simultaneously, then I think best approach is to use UIScrollView with the images added in the correct placed "by hand." UITableView and friends is not built to handle non-lined up columns.
added If you do use a UIScrollView, and you have a large number of images you want to display (that is, the user can scroll for a long time), then it would be wise to recycle your UIImageView objects that are scrolled off the screen. This is what UITableView does with UITableViewCell objects, and that's why UITableView wins. You can win, too, if you code carefully.
Three table views would work, but in order to keep things neat and from the same datasource, I would consider using a subclassed UIPickerView and the UIPickerViewDelegate/UIPickerViewDataSource.
Particularly necessary methods:
// UIPickerViewDataSource
– numberOfComponentsInPickerView:
– pickerView:numberOfRowsInComponent:
// UIPickerViewDelegate
– pickerView:rowHeightForComponent:
- pickerView:viewForRow:forComponent:reusingView:
According to my opinion You should have to take three UITableView in xib file and take its IBOutlet then give each UITableView an unique tag and then implement UITableView's Delegate methods and in that Methods Check for Tag and then assign values.
Along With this, the other solution, you can also use UIPickerView and then implement UIPickerView's delegate methods also..
Happy Coding !!!
do anyone have experience with UITableView inside a custom UITableViewCell ?
I had a try and the UITableView in the UITableViewCell looks like that can't respond to user inputs (i.e scrolling).
Before going any further I would like to know if I am wasting my time !
Does anyone have seen something like that around ? Any reference would be helpful.
Thanks
I haven't done this, but I discourage this. This could cause odd things to happen.
In a similar vein, Apple says not to use UIWebView inside of a UIScrollView. The reason is because a web view is a subclass of the scroll view. Nesting them can cause unexpected behaviors. Note that the table view is also a subclass of the scroll view. While Apple doesn't explicitly mention your case, I assume that it is the same idea.
If yo must, subclass UITableViewCell and see what happens. It's not that difficult. Make the cell implement the UITableViewDelegate protocol.
Since the parent TableView responds to the vertical swipe gesture, your child TableView is not going to ever see it. Where should the swipe gesture "go"? It has to go one place or the other, so one of the TableViews will always not behave "correctly". I do think that trying to put a TableView inside a TableViewCell and getting it to work just like a root TableView is probably a waste of time.
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 implement a filmstrip-like UIScrollView that will be populated with thumbnails of catalog pages. Selecting a thumbnail image will cause the main UIScrollView to move to the selected page. The Catalog may contain 100 - 200 pages, and I want to load them lazily only when required.
I have done this in a UIScrollView with paging enabled, but haven't seen anything on the best way to do this in a non-paging scenario. There will be 6 thumbnails visible in the UIScrollView (+ 1 when the view is being scrolled) at any one time. I want to dequeue and reuse the thumbnail's UIView when the view is scrolled, as I am doing in the main UIScrollView (which is a paging scroll view).
Thanks -
Jk
I am also going to suggest you take a look at some sample code of Apple, that is, Photo Scroller. If you are a registered iOS developer, you should also take a look at the WWDC10 session about scroll views in iPhone applications.
http://developer.apple.com/library/ios/#samplecode/PhotoScroller/Listings/main_m.html
What you need to do is mimic the behavior of a table view (which is nothing more than a subclass of UIScrollView). What you should mimic is the reuse of the cells. It is pretty easy to implement and will dramatically reduce the memory foot print of your application since you only load the content that is currently visible in the scroll view.
I hope this helps.
Check out the scrollview suite sample code from apple. The tiled example can probably be repurposed very easily.
http://developer.apple.com/library/ios/#samplecode/ScrollViewSuite/
Check out this class..it may proove helpful..
VSScroller
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. :)