This may be a general discussion instead of a real question. When I started using NSTableView and NSOutlineView, I thought : oh, a instance of NSView may do almost everything. So I return a NSView instance in my delegate and dataSource.
Of couse it did not work and I realized that NSTableView consitsts of instances of NSCell which inherits directly from NSObject.
I sensed that it may be important to understand why Cocoa constructed NSTableView based on NSCell but NSView. But few documents explain it clearly. Therefore I turn to Stackoverflow. Does anyone know that? Thank you at advance!
You can switch to a view based NSTableView or NSOutlineView in the inspector
The reason for a cell based cell would be if your only want to display a string. If you only want to display a string it would be a waste of resources to init a whole view to each cell. It is basically about memory control vs. what you need to display.
#d00dle's answer shows how to use an NSView backed table view, but it doesn't answer the question of why NSTableViews historically used NSCells in the first place.
The answer is that NSViews are heavy objects and expensive to manage. NSTableViews typically need many many rows and columns of "view-like" things, and if you naively added them all as actual NSViews, you can't maintain a responsive UI.
This is reflected in the trickiness Apple added to support NSView-backed table and outline views; it creates a limited number of NSViews and recycles them in clever ways to reduce the total number of NSViews in use at any given moment.
Related
I am developing my first app for OSX. Sorry for asking stupid questions. I have spent a few hours trying to figure this out on my own, with no luck so far.
I want to make an iTunes-like interface. I used NSSplitView, placed NSView for navigation and NSTableView above that. [I am aware that there better alternatives to NSSplitView, yet my goal is to both - develop an app and also to learn Cocoa/OSX in the process.]
Atop NSView panel designated for navigation, I am trying to place NSTableView. However, my table is not being displayed. I therefore have questions...
I understand that for cells to be populated, controller must implement NSTableViewDataSource. I tried that, but was so far unsuccessful - to the point that I don't see the table. Please advise:
Can I have a working NSTableView-derived custom class also implementing NSTableViewDataSource? If this cannot work, please advise why or point me to an explanation.
Am I correct in thinking that all elements can be manipulated programmatically, in the sense that I use IBOutlet in headers to point to the right object, yet do nothing with InterfaceBuilder - have everything controlled from within my Objective-C code? Do I have to use IB?
Thank you.
Yes that will work but it's an unusual approach. Generally the tableview delegate/datasource is something enclosing the tableview. You'd normally only subclass NSTableView if you require some additional functionality not provided by default (for me that has been custom behaviour to input).
Yes you can do it all programmatically, however you will find it much easier to use IB. The IB-loaded views are created programmatically under the hood, using the information contained in the nib file. You will find it long-winded and tedious pretty quickly.
WRT to your issue with not seeing the table, you will need to add logging/breakpoints on the few key delegate/datasource methods to ensure they are being called (start with the daddy of them all numberOfRowsInTableView:). If they are not then you aren't setting the delegate/datasource correctly in the tableview.
I have a simple case of an iOS application I would like to measure: a UITableView built with custom extended cells. Each cell is a composition of a main views and some subviews. Based on some criteria I am hiding or showing subviews in table cell.
Supposing I have to decide if adding subviews when needed, or built xib with all the outlets and hide/show when needed.
What could be the best approach for deciding between those two ?
Supposing also you didn't read Apple guidelines about composition of cell, what concrete steps you would do either via code (by putting NSLog statement for example), or via Xcode instruments (which one to choose etc...) to confirm the choice.
This is quite a new matter for me, so please be as much specific as you can.
This http://blog.giorgiocalderolla.com/2011/04/16/customizing-uitableviewcells-a-better-way/ is a great resource.
Having many subviews with transparent backgrounds degrades scrolling performance.
Dynamically adding subViews could get difficult to track, and if you don't do it "right" then you'll end up with cells with too many "extra" subviews, via the cell reuse queueing mechanism.
You'll have to add the subViews in the init method of the cell itself and not in the cellForRow method of your data source. (unless you're using some way to track the creation/availability of any given subview, like viewWithTag etc.)
I have a NSTableView that holds a name to all of my NSImageView's, and depending on the order that the NSImageViews were added, the last one would be in the front.
But in the case that I want the user to be able to bring a NSImageViews in front of another, how would I do that?
Thanks in advance.
As explained on the NSView reference page, the z-order of a view's subview is given by their oder in the view's subviews array. You can insert a new subview relative to the others using -addSubview:positioned:relativeTo:, and you can reorder the existing subviews by getting the subviews property, reordering the views therein as you like, and then calling -setSubviews: to set the new order.
Specifically, the docs say:
The order of the subviews may be considered as being back-to-front,
but this does not imply invalidation and drawing behavior.
What you are asking about, I think, is how to control the z-order of views.
For historical performance reasons this is not well supported in AppKit (unlike UIKit in iOS), since until somewhat recently you couldn't actually have sibling views that overlap.
A common approach to this (on recent OS X releases) is to use Core Animation (in particular, CALayer) which does support z-ordering natively, but this is probably overkill for what you need (and in any event is going to have a learning curve for you).
What are you actually trying to do? Are these images (image views) precisely on top of one another? If so, the easiest (and much better performing) approach is to have a single NSImageView and to just send -setImage:... to it to change the displayed image.
How would I make an NSCell with more than one UI element in it and display it in an NSTableView? For NSCells with a single value I could implement tableView:objectValueForTableColumn:row: but I don't know how to do this for NSCells with more than one. At the moment I have an NSView in an NSCollectionView and all the elements are bound to an NSArrayController. But I'd rather have an NSTableView or similar.
I've switched to JAListView for table and outline views in my Mac apps: https://github.com/joshaber/JAListView
It has the advantage of using NSViews for table items instead of NSCells, allowing for greater freedom in implementing your design.
There's a few other alternatives out there too trying to solve similar gaps in NSTableView and its subclasses:
http://groups.google.com/group/cocoa-unbound/browse_thread/thread/87b2a1b5725eac05
You return the primary value in the tableView:objectValueForTableColumn:row: method, and then set up the cell further in tableView:willDisplayCell:forTableColumn:row:.
Either that, or you create a custom NSCell subclass that can customize itself based on the objectValue that you give it.
I've got an NSTableView that displays (via bindings) data from an NSTreeController. The application frequently appends/changes data to/in the bound array.
The problem is that if the user has selected a row in the table, but has scrolled so that the selected data is no longer visible, when the application updates the array it causes the display to auto-scroll so that the selected line is once again on screen. This is pretty
frustrating to users, especially since new data can arrive at any time.
Is there any way of disabling this feature?
You may have to subclass NSTableView and override -scrollRowToVisible:, temporarily bracketing the call to super. This may also require a custom BOOL ivar in your subclass to keep track of whether you want to scroll.
I would start by setting a breakpoint there to see when exactly the autoscroll is triggered. This should help to find the proper moments to toggle the ivar.
Are you using an NSTreeController with an NSOutlineView or an NSArrayController with an NSTableView? Using an NSTreeController with an NSTableView doesn't make a lot of sense to me?
If you're using an NSTableView you should probably be using an NSArrayController to manage its data and this rearranging of the rows is a feature of the NSArrayController. Try turning off the Auto Rearrange Content option on your controller within IB.
When it's on, the array controller will rearrange its objects on addition, removal and changes to objects that would affect the sort ordering (if any) and cause any table views or outline views to reload their data.
I don't know of a similar feature for NSTreeController mainly because I don't use it since it's never worked well for me. I, sadly, recommend to just use the datasource methods for the NSOutlineView and supply your data the old-fashioned way. In my experience, NSTreeController is only well suited for the most trivial tasks.