I am building a small Search app on iPad. I want to show the search results. Do I use UIScrollView or UITableView?
The number of search results are unknown & as the user scrolls vertically I'll want to dynamically keep fetching the results & fill whatever container I will be using. Something like what Google Reader (on web) has.
For this purpose which is better suited? UIScrollView or UITableView? Also please guide me as to how dynamically populate the results?
This is an awesome question. I have a different approach for a solution to this problem. It is not the exact answer; But I would assume that the logic might be helpful -
Algorithm:
Decide on a certain number of records being pulled into the UITableView. (lets say 8 ).
You can use a UIScrollView with a small size (rather than setting it with smaller stepping size & frame).
Using the clipsToBounds property (set it to NO), you can actually track the amount of scroll, and check if it goes out of bounds
After you go beyond the bounds, initialize a new UIScrollView with a fresh-list of tables, and get another 8 data entries, and this can be continued.
Reduce the size, set the property and it would work.
But the problem with this is that ; if you try to touch outside the scrolling area => it will not scroll up/down.
Please refer to this tutorial, which can offer some intel on this idea.
And for setting the Scroll amount for Page control => Refer to this question on Stack Overflow.
Related
I'm trying to understand how autolayout works under XCode6, but there's a lot of mysterious things that runs away from my mind. Autolayout and constraints philosofy can be very hard to learn, but I realized that life can be easier using these tools...
For your information, I need to build a chat view with a table (the messages) and a view containing a text field (the send message pane) nested in a UIView that is again nested in a UIScrollView, so I can shift up the scroll view as the keyboard appears under the textfield.
I read a lot of tutorials and watched a lot of video until I found the useful tutorial Using UIScrollView with Auto Layout in iOS. There's a Xcode project in Github of what the tutorial explains, too.
In his tutorial, Mike Woelmer tells that
One of the big pain points with the old way of setting up a
UIScrollView was communicating the content size to the scroll view. It
was fairly straightforward to calculate your content size if the
content in the UIScrollView was an image. But it was not as easy if
your scroll view included a mixed bag of buttons, labels, custom
views, and text fields. Lengthy code adjustments were needed to
reflect constant changes in device rotations and phone size
differences.
So Mike explains the way to adapt the UIView, using placeholder and forcing the view inside the scrollview to fits the device's screen, creating in viewDidLoad some NSLayoutConstraint:
The solution is to look outside the scroll view and attach a
constraint to the view controller’s main view. This cannot be done in
interface builder, so we will have to write some code. Interface
builder is still complaining, though, so we have to add a placeholder
width constraint to make it happy.
I tried to use parts of the code of the tutorial for my project, but I cannot get a working view controller for my needs (I always get errors). Which is the best approach to do this? Am I on the right road?
Last but not least, I'm italian, so pardon for my english. If something is not clear enough, please leave me a comment.
Basically you have to set both alignment and size constraints in order for Autolayout to take care of the rest for you. If you don't provide enough information you get warning. If you provide conflicting information you get errors.
You need basically to provide enough information for Autolayout to calculate the UIView frame property (i.e., x-position, y-position, width, height).
For example, by providing the distance constraints from the top, right, bottom, and left edges, Autolayout has enough information to draw that UIView's frame rectangle. But you could also provide just the distance constraints from the top and left edges and then provide a size and height constraint.
You can also configure the key constraints you need and then click 'resolve auto layout issues' and choose 'add missing constraints' though sometimes it doesn't give you what you want. It is better to understand that how Autolayout accomplishes what I described above.
If you mess up, it's usually easier to clear all the constraints and start over. Do it a few times and you'll get the hang of it.
I would like to make a table-view with expanding ability.
When you press a row, the row should expand to show options like delete, copy and so on.
I have found an example for iOS, but I didn't get it running on Mac OS X, because NSTableView and UITableView are very different.
http://www.cocoacontrols.com/platforms/ios/controls/kofiles
Has anyone another template?
Or maybe even get this example running on Mac OS X?
I don't have code to hand you but you can use a view-based NSTableView. Your prototype view can resize itself to include controls if it's selected. All that's a bit complex to condense into a reasonably brief answer but if you use a view-based table view and treat the prototype view like any other that would grow and show extra controls, then wire this behavior to the selection state, it should work.
Note: you will have to write some code for the expansion portion, to handle resizing it, showing the controls, and notifying the table view that one of its rows changed height. Lots of documentation and examples exist out there for each individual component of your problem. Post more specific questions as you run into roadblocks.
Initially I was under the impression that it uses the table row slideup/down animations while inserting/deleting new rows but I doubt if it's doing that as it does it so fluidly even with thousands of items in the list (otherwise it would take a lot of time for the deletions/insertions to work).
Am I right in my assumption that it's simply attaching a new instance of the News list at the bottom of the screen, shrinking the above one while the one at the bottom expands to fill up space?
UPDATE:
Please see this video of what I mean: http://dl.dropbox.com/u/4960327/ReederAnim.mov
I can not tell you exactly how Silvio Rizzi made this, but as you see in the playback, a list view is added behind the shown list view, and the front list view fades out (.alpha = 0.0;) while the list view behind it expands its height per row.
When you desicate it frame by frame it becomes quite clear what he does, and it is really not that advanced. But I have to admit, with the white "milky" polished interface, it looks quite neat.
In addition, you can see that while animating, the background list view only renders the top 7 entries (hopefully calculated by dividing the view height with the average height of the cells shown) making the list view quick to load. Then afterwards, he can load an extended array of cells once you start scrolling, or in a background thread starting once the animation is complete.
I am relatively new to Objective-C and iOS development.
What I want to do is have it that I have an array of length 52 representing a deck of cards, with each value in the array corresponding to a card image. When a button is pressed, the card that comes out will appear in an image view (already done), as well as appear as the right most element in a horizontal scroll view.
I do not however know how to do this in Objective-C, neither the horizontal view nor the appending to the end (or right).
Any help will be much appreciated,
Thank you very much for your time.
AB
What you're looking to do is called Paging with a UIScrollView. Download the "Page Control" Sample project by apple here :
http://developer.apple.com/library/ios/#samplecode/PageControl/Introduction/Intro.html#//apple_ref/doc/uid/DTS40007795
Think of each page in that project as another card. You can add/subtract from it whilst the program is running. You can take a look at my open source "Dollar Bets" app on github for another example here:
https://github.com/Rich86man/Dollar-Bets
Check out MainViewController
I'm developing an application that requires me to display many short strings of text in table cells. Currently, I'm using a default table view cell with about 14 UILabels added. Half of these labels contain static text that will not be changed, while the other half contains dynamic data that has to be updated when the table is scrolled.
As my clients are complaining that the table is lagging, I am wondering if there is a more optimized way to display the data, and improve scrolling performance. For example, would the table cells render faster as the table is scrolled if the fixed text is rendered directly onto the view, instead of being contained in UILabels? What other methods can I use to improve scrolling performance?
Performance issues in table view scrolling can be caused by any number of issues. For example:
Make sure the UILabels are opaque to avoid blending. (You can select the color blended layers option in the Core Animation instrument to verify this).
Make sure you're recycling table view cells by using dequeueReusableCellWithIdentifier:
It might be helpful if you could post your implementation of tableView:cellForRowAtIndexPath:
additionally to anshuchimala's answer i would recommend you to remove the static labels and integrate it into a UIImageVie which you use in your tableviewcell as a background image.
Apart from that opacity (as mentioned by anshuchimala) is a big performance-blocker, but also the extensive use ofNSDateFormatter instances can vastly decrease your performance (especially the instantion of NSDateFormatter instances need a lot of power)