UIActivityItemSource协议代理方法未触发问题求助（iOS/Objective-C）

Hey there! Let's break down why your UIActivityItemSource protocol methods aren't triggering—this is a common pitfall, so here are the most likely causes to check:

• Incorrectly passing the source object to UIActivityViewController
  Make sure you're adding your UIActivityItemSource-conforming object directly to the activityItems array of UIActivityViewController, not just passing raw data. For example:

  // Correct: Pass your source object
  let activityVC = UIActivityViewController(activityItems: [yourCustomSource], applicationActivities: nil)
  
  // Incorrect: Passing raw data skips the source methods
  let activityVC = UIActivityViewController(activityItems: ["Default text"], applicationActivities: nil)
  

• Mistyped protocol method signatures
  Double-check that your method names and parameters match exactly. The two required methods are easy to miswrite:

  • activityViewControllerPlaceholderItem(_ activityViewController: UIActivityViewController) -> Any (returns a placeholder matching your final data type, e.g., "" for text, UIImage() for images)
  • activityViewController(_ activityViewController: UIActivityViewController, itemForActivityType activityType: UIActivity.Type?) -> Any? (note the optional UIActivity.Type? parameter)
    In Swift, avoid marking these methods as private—they need to be accessible to the system.

• Early deallocation of UIActivityViewController or source object
  If your UIActivityItemSource instance is a local variable, or the UIActivityViewController isn't strongly referenced, it might be deallocated before the share sheet loads. Fix this by holding a strong reference, e.g., in your view controller:

  var shareSheetVC: UIActivityViewController?
  
  func presentShareSheet() {
      let source = MyActivityItemSource()
      shareSheetVC = UIActivityViewController(activityItems: [source], applicationActivities: nil)
      present(shareSheetVC!, animated: true)
  }
  

• Activity type filtering or nil return values
  If you've set excludedActivityTypes on the share sheet, some activities won't trigger the methods. Also, if you return nil from itemForActivityType for a selected activity, the system might not process your data (though the method should still fire).

• Missing protocol conformance declaration
  Ensure your class explicitly declares conformance to UIActivityItemSource and inherits from NSObject (since this is an Objective-C protocol):

  class MyActivityItemSource: NSObject, UIActivityItemSource {
      // Implement required methods here
  }
  

If you're still stuck, sharing a small snippet of your UIActivityItemSource implementation could help pinpoint the issue!

内容的提问来源于stack exchange，提问作者user6631314