I am trying to support infinite scroll in tableview.
I know tableview lets scroll infinitely, but my case is different.
Initially, I will load 30 items in my tableview as the user scrolls down close to 30th element, I will make a http request to get next 30 items so its not like I am loading 60 items at once.
My way about going to do this is when my table is initally filled with 30 items, once the footerview is seen, then I will request the next 30 items.
My question is how to detect footerview is seen? Is there something like 'will appear' for just footerview?
Let me know if there is other better way of completing my scenario above
Thanks!!
A UITableView is a subclass of UIScrollView, and UITableViewDelegate conforms to UIScrollViewDelegate.
So you can set yourself as the tableViewDelegate and implement scrollViewDidScroll:. You can then either check the scrollView.contentOffset yourself, or call [myTableView visibleCells]. I am sure there are various other methods as well.
The behavior you are trying to implement is known as pull-to-refresh.
There are several implementation of it already available, e.g.:
https://github.com/leah/PullToRefresh
https://github.com/enormego/EGOTableViewPullRefresh
Give it a try, or read the code the learn the details. If you are curious, the way the trick is done is by implementing the delegate methods for the scroll view and checking the value of scrollView.contentOffset.y.
Related
I have a UITableView in my application. When the table is scrolled almost to the end, I download more data and reload the table.
If the tableView was scrolling, at the time I call [tableView reloadData]; scrolling stops. How can I achieve effect of not stopping the scroll meanwhile reloadData? I think I need to somehow save scrolling speed and then restore it, but how to do this?
P.D. I really searched this question before asking.
I thing, this method (insertRowsAtIndexPaths:withRowAnimation:) is the key.
There is a use case and a nice tip described on SO: the use case and the tip.
Since UITableView is subclass of UIScrollView, you can use UIScrollViewDelegate's scrollViewWillEndDragging:withVelocity:targetContentOffset:
method to determine how far it is supposed to scroll and then after table reload call setContentOffset:animated: with that target offset (or beginning/ending of tableview if it becomes smaller) to simulate continued scrolling
EDIT: since your targetContentOffset is probably going to be CGRectZero, you will have to recalculate it somehow using velocity from the same method
if i am not wrong you are looking for a function call Lazy load. I can recommend you to search SVPullToRefresh
here!
I'd like to implement a feed in iOS 7 that is only pulling new data if it appears the user has a chance of viewing it. I know UITableView is a subclass of UIScrollView that does this well, but I can't get the cells to behave the way I'd like - I'd like it to look similar to facebook or twitter's newsfeed where you can reload by pulling down and load more by hitting the bottom.
I've seen other questions such as this but I'm looking for vertical scrolling only, with absolutely no horizontal movement. I'd like to use a method calling (for example) nextTenPostsFromIndex: that instantiates from zero, and applies to whatever index was the last on the screen if hitting the bottom.
My question: Is the best way to go about this to create a UIScrollView, place a subview inside of it, and programmatically space them on the available scrollview space, and apply the same drawing methods again with repopulated data if nextTenPostsFromIndex is called or checkForNewPosts (if pulling down from the top)? Would this be a reasonable way to implement Facebook's iOS7 newsfeed, or others like it?
Short answer: No. You really ought to use UITableView for things like this. You can use a custom cell or whatever you want. If it helps you, also know that since UITableView is a subclass of UIScrollView, you can do anything you would normally do with a scrollview, including assigning a delegate which acts based on the current position when scrolling.
Ok, so I have a normal viewController that has a UIScrollView in it that gives details about distilleries. What I wanted to do was have a list of spirits that are distilled at the distillery that they are reading about. So I attempted to implement a UITableView inside of my UIScrollView, and after hooking everything up and writing all the delegate and datasource methods I come to find out that a UITableView will not work inside of a UIScrollView. So does anybody have any ideas as to what kind of User Interface Object I can use to accomplish something like a UITableView's dynamic characteristics? I don't want to use a UITextView because it just looks cheap and unstructured. I need something that can dynamically change the number of items shown because not all distilleries will have the same amount of spirits distilled there.
If you are implementing a UITableView, there is no need to create a UIScrollView.
As a UITableView will automatically increase its size and behave like a scrollable view whenever the content size is larger than the screen.
I've been searching a ton and can not seem to find an answer...
I have a tableView which scrolls all the days of all the months. And I have a titleForHeaderInSection: and viewForHeaderInSection: which displays a section header at the top of each month-section which replaces appropriately at the top, cool. But how can I create a single header where the titleLabel changes to the proper month as I scroll (in other words, Not have multiple section headers, just one)?
I can't tell whether this should be setup as "one (big) section with a header that changes" or "a headerView that changes", or whatever... Any examples would be greatly appreciated. Thank you in advance.
You can create a static view and place it above your tableView. Then you can use the visibleCells property to determine which cells are visible. When those cells change to the cells of a new section you can update the static view that is above the UITableView.
Once you are the delegate of the UITableView you are also the delegate of the UIScrollView it is built on.
So you can catch the scrollViewDidScroll: delegate call and update your header there.
So to lay it out:
1.) Create a Header View above your UITableView
2.) Become the delegate of the UITableView
3.) Implement the scrollViewDidScroll: method to detect scrolls
4.) Inside the scrollViewDidScroll method use the visibleCells property of the UITableView to determine which cells are being shown and to update your header view appropriately.
I've never done anything like this, but I don't see why it wouldn't work.
EDIT: As Husker Jeff pointed out. It is probably easier to use indexPathsForVisibleRows to determine what is on screen. You can then use that fairly easily to determine which section/sections are being displayed. Thanks Jeff!
Maybe I'm missing something obvious, but I'm have a hard time programmatically setting the row selection in a tableView. The goal is to simply have a tableView open with a row already selected. The problem appears to be that I have to wait until the tableView is fully loaded before I can modify the selection.
I've read various strategies such as calling reloadData for the tableView in the viewController's viewWillAppear method, then immediately calling selectRowAtIndexPath for the target row. But when I do that, I get a range exception because the tableView has zero rows at that point. The UITableViewDelegate methods (numberOfRowsInSection, etc.) don't appear to be called immediately in response to reloadData (which makes sense if the table rows are drawn "lazily").
The only way I've been able to get this to work is to call selectRowAtIndexPath after a short delay, but then you can see the tableView scroll the selected row into view.
Surely, there's a better way of doing this?
Well, you can use another strategy. You can create a hidden table view, configure how you want and than show to user. Use the tableview.hidden = YES.