问题
I couldn't find a good answer anywhere to this. I am using a UINavigationController for my iPhone app, with everything is generated programmatically, nothing in Interface Builder. I am trying to port my app to iPad, using a UISplitViewController and my existing UINavigationController, but I am not sure where I should have the logic of my program separating the view controllers for iPhone or iPad.
Do I set up my main file to use a different app delegate or do I use the same app delegate and have the user interface conditionally set up within it?
Besides this, whenever I try to compile my app on the simulator it does not recognize the UISplitViewController or even the condition in which I check if the class exists.
Can please someone put me in the right direction, remembering that I am not using any xibs?
回答1:
If you want to see an example of a completely programmatic iPhone / iPad interface that uses a split view, you can download the source code of my application Molecules.
Within that application, I use one application delegate, but I set up the interface differently depending on which user interface idiom is present (iPad or iPhone). For the iPhone, I instantiate a root view controller which manages the appropriate interface for that device. For the iPad, I first create a UISplitViewController and attach it to the root window, then create my iPad-specific root view controller and place it as the detail view of the split view controller (with a navigation controller that I use for item selection as the left-hand controller for the split view).
Again, I recommend looking at that application project to see how I set this up programmatically. The code's available under a BSD license, so you can copy and paste this into your own application if you'd like.
As far as the compilation errors you're getting, you will need to migrate your application target to be a universal application using the "Upgrade Current Target for iPad" menu option. Once that has completed, set your build SDK to 3.2. Go to your application's build settings and set its Deployment Target to the earliest OS you want to support with your application (with 3.0 being the farthest back you can go).
Finally, you will need to weak-link UIKit. For how to do that, see my answer here. Weak linking of frameworks is no longer necessary if you are building using the iOS 4.2 or later SDK. Simply check for the presence of the appropriate classes at runtime by seeing if their +class method returns nil.
来源：https://stackoverflow.com/questions/2796587/how-do-i-make-a-universal-iphone-ipad-application-that-programmatically-uses-u