I have several parts in my app where I use custom table view cells.
Their content is created with subviews.
The problem is that on some of these cells, the content does not appear at all or does not appear correctly until after the cell was selected for the first time.
One example is a custom cell which has a custom subview which can be set after its creation. This view does not appear at all before I selected the cell and its views were redrawn. Calling -[setNeedsDisplay] in the subview's setter method does not help either.
The problems was that I was using the cells themselves to calculate their height. For some reason, the subviews (which were part of the cell used to calculate the height) weren't appearing correctly in the cells that were used for the actual displaying.
Therefore my advice: Never use a UITableViewCell to calculate its own height. This may work in principle (it doesn't crash), but might bite you later in unexptected and hard-to-debug ways.
Related
I am creating a grouped table with two sections.In the first section i have 5 cells and in the second section i have two buttons in the lass cell of it.
I have created labels and buttons on each of the cells in the first section and the labels are populated dynamically by the values selected in the previous screen.
Everything works fine as expected,except the borders of the table view gets ruined,it looks like half drawn and incomplete.When i make the table view to scroll up and when its back in the original position,the top borders are spoiled and when i scroll to the bottom the lower borders of the group gets affected making them incomplete.
I am setting the label's and button's attributes in each of cell after initializing them in the viewDidLoad method.
Please suggest me an idea to solve this issue.
Thank you one and all
I am setting the label's and button's attributes in each of cell after
initializing them in the viewDidLoad method.
This is incorrect. You should save the texts for the labels & buttons in a model class & set them in the cellForRowAtIndexPath: method. As, you are not doing this in the aforementioned method, your cell is redrawn when you scroll and the texts are nullified.
I´m new trying to make some apps using objective c, so I´ve an idea using uitableview but I don't imagine how can I get this.
I´m trying to do something like you do in a spreadsheet where you have a fixed header and the first column too
So when scroll the uitableview vertically the header will stay visible at top of the table and rows will change
And finally when you scroll in horizontal direction the first cell of the row will stay visible and will change the header depending of how you scroll the uitableview
I hope you could give me an idea how to get this, because I don't imagine how to do this, also I don´t have a lot of experience with this programming language.
Thanks!
In a non-grouped table, section headers "stick" at the top of the table as the table scrolls. You can provide a custom UIView (or sub-class thereof) for a section header through the delegate method –tableView:viewForHeaderInSection:. This header view could be created on-the-fly programmatically or loaded from a NIB file. Either way, you can have it contain whatever you want, even update it as the app runs (provided you have given yourself access through ivars or class variables to the views contained in your header view.) If you go this route, you'll want to be clever about allocating resources that comprise this view, so that you are not constantly allocating new resources! This delegate method can be called frequently, and on all but the first call you could simply return the previously created (but updated as and if necessary) header view.
UITableView isn't designed to do this, although I am sure you could figure out some way eventually.
My approach would be to use a fixed UIView of some sort (possibly a UILabel, etc) in a UIViewController's nib as the header/locked cell, and add the UITableView under that. You couldn't then use a UITableViewController, but would have to implement the delegate and dataSource methods in your UIViewController, and use a UISwipeGestureRecognizer to pick up the gestures from the tableView and update the other views.
I've done this by adding a UIView that mimics the first cell in my table. In my case I am using a subclass of UITableViewCell, but that is perhaps not relevant. Normally this view is hidden with an alpha of 0.
If you view controller is the delegate of the UITableView then it will also be the delegate for the inherited UIScrollView. So in your view controller you can implement scrollViewDidScroll. When the scrollView's contentOffset is positive I set my custom view's alpha to 1 (I also do some small size tweaks to make sure there is a perfect match), and when the contentOffset returns to 0 or negative, I reset the alpha back to 0.
prepend the first row of data in your array to what ever in the first row is your headings, put the text in bold with attributed text, It wont be sticky but you will have headings...
I have a UIView (created in IB) with a grouped UITableView as a subview. Below this table view is a UIButton. The XIB containing the view will be loaded by a few different viewcontrollers, and so the contents of the table view can vary between one and four cells.
Here's what I want to achieve: when the view loads, the height of the tableview (tableView.frame.size.height) should be adjusted depending on the number of cells, and the button should be placed just beneath the table view.
Can this be done? Could it somehow be done if the view is created programmatically?
Thanks in advance
Edit: Pxl's suggestion was just what I was looking for. A while later, the need arose to have more than just a button below the table view - this was accomplished by creating a separate view containing everything I needed, and implementing the tableView:viewForFooterInSection: and tableView:heightForFooterInSection: functions.
A note for those of you trying to do the same thing: the tableview has to be programmatically created if you want different heights for the footers, or footers for only some of the sections. This is because the footer height set in IB will override the one returned from the tableView:heightForFooterInSection: function.
if there are only a handful of rows, may i suggest that you create a special UITableViewCell that contains just a button?
then make that button cell the bottom row of the last group all the time. make the group so that it will be unlabeled and appear as if the button is sitting at the bottom of your tableview. this way you won't have to muck around with recalculating the tableview's frame and redrawing it.
if the tableview will scroll due to there being many rows, then you'd be calculating the height of the tableview up to a set max (at which point the tableview will need to scroll to show more rows).
once you've determined the height of the tableview you'll need to display your rows, make a frame of the appropriate size, set the tableview's frame to it, position the button just under the tableview, and then redraw the view.
the layout and positioning in this case will need to be done programmatically.
UITableview is a subclass of UIView, so you can change its frame to suit your needs just like a UIView, and UITableView will manage drawing itself to whatever frame you give it.
Just use the methods UITableViewDataSource and UITableViewDelegate provides you.
height = [self tableView:numberOfRowsInSection]*[self tableView:heightForRowAtIndexPath:] + A_CONSTANT_FOR_HEADER_AND_FOOTER_HEIGHT
I agree with pxl that adding a cell with the button in it may be the easiest way to accomplish what you want.
Whether or not you do that, the table view's sizeToFit method should resize the view to (just) fit its contents. If that doesn't work, you can use numberOfSections and rectForSection: to build a loop that determines the height of the table's contents, and reset its frame manually. (And then position the button underneath.)
On an iPhone, how do you figure out the width of a table view cell's content view when it is showing a certain accessory view (disclosure indicator, etc)?
I need this in order to calculate the correct cell height for cells that contain wrapping, variable-length text. But when the table view delegate is asked for a cell height, it doesn't actually have the actual cell instance, so it can't just query the content view bounds directly.
I can easily hard-code a 20-pixel margin on the right which appears to be accurate for a plain style table view in portrait orientation with a disclosure indicator, but would prefer to do it the Right Way so that it keeps working if Apple decides to tweak the margin.
(This is related to this question.)
Personally, I would just hard code the values -- simpler and things will break in a predictable way.
But were I to do this programmatically, I would create a UITableViewCell, set up the editing properties / accessory views you need to measure, and then ask it how big its contentView is.
Of course I would probably heavily cache this -- doing allocations when asking UITableView asks you for height information sounds to me like it would be slow (check with a profiler first though, as always).
I would have a subclass of UITableViewCell that holds all its subelements. You can cange the frame of certain elements when the cell enters and exists editing mode. There is a good example of this in Apple's Table View Programming guide under the section on creating a custom table view cell.
I believe the UITableViewCell's contentView property is the view that contains your labels etc., so the width of that should be your available size to use.
I want to resize my table view cells from inside the cell instead of from the UITableViewDelegate. I am resizing them based on asynchronous content, so I can't size them in the delegate.
I tried setting self.frame inside the cell, but the table view was really unhappy about that. Cells were overlapping and all kinds of craziness was going on.
You simply have to use the table view to control height. You can tell the table a cell has altered by using the calls to remove and then re-add specific cells, so you don't have to reload the whole table - but the height has to be fetched using the delegate callback tableView:heightForRow:atIndexPath:
I don't see why this is not practical though. You can have any number of asynch systems running that update a central height cache held by the table view delegate - every time you create a cell you can assign it the delegate as a reference so it has a way to talk back to the table and let it know cells need reloading and what the new heights are.
If you think about it, the poor table view is a scroll view that has to manage all these separate cells and keep them together visually - so it's really unkind of a cell to go rogue and start altering frames without letting the table view know what is going on anyway. It's best to let the table drive and tell it what to do.
No you can not set the cell's size without using the UITableViewDelegate. Changing the size of the cell with actually change the size of the cell, but it will not change the offsets that the UITableView draws the cells with. Which will result in overlaps, and gaps all over the place.
Your friend is tableView:heightForRowAtIndexPath:, and it should be fast. If you override it, then the table view can no longer make the assumption that all rows are of the same height. And thus it must query all rows for their height each time it fetches cells to draw.
You should try to manage the cells contentView propertys frame, instead of the cells frame itself
heres a reference http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UITableViewCell_Class/Reference/Reference.html#//apple_ref/occ/instp/UITableViewCell/contentView