UIDocumentPickerViewController blocks UI while importing files from iCloud

Number:rdar://27844889 Date Originated:15-Aug-2016 01:08 PM
Status:Open Resolved:
Product:iOS Product Version:10b5
Classification:UI/Usability Reproducible:Always

When importing files from iCloud using a UIDocumentPickerViewController configured for import (UIDocumentPickerModeImport), the iCould Drive UI completely blocks user interaction, making it appear as the app has became unresponsive. 

The activity indicator in the toolbar animates (see iCloud.png), but no touch interaction is processed (buttons can’t be pressed, scrolling is not possible, etc.). This state can take several minutes to complete for large files that have not yet been cached locally by iCloud. This is especially bothersome on slow networks. 

Steps to Reproduce:

Upload a new large file to iCloud. Then immediately use an app that supports UIDocumentPickerViewController in import mode to import the new file. Observe the UI becoming unresponsive during upload. 

You can use Dropbox (14.2.2) to test this. Use the central “+” button, select “Create or Upload File”, “Upload File”, “iCloud Drive”.

Expected Results:

- The UI should show determinate progress during the import process. 
- It should be possible to cancel the import process. 
- It should be clearly indicated that the UI is currently disabled (by say graying it out). 

Dropbox does a much better job in this case (see Dropbox.png). 

Actual Results:

The import UI blocks (potentially for several minutes), without any precise progress indication or the ability to cancel the import operation. In addition, due to blocked user interaction, the app appears to hang, which might promote the users to kill it. 


Observed on both iOS 10 and iOS 9. 


We considered using UIDocumentPickerModeOpen as a workaround, by manually copying files into our sandbox. However not all file providers support this mode. We rely on those providers being available and can thus not switch away from UIDocumentPickerModeImport for the time being. 

We received a lot of user complaints for various issues related to UIDocumentPickerViewController. Due to this being a system component there is really nothing we can do on our own to fix the issues. At the same time, it appears like this is an app-provided UI, which means the users automatically blame the app for any issues.


Duped as rdar://27844932


iCloud: https://cloudup.com/cGyRH9-KzWX Dropbox: https://cloudup.com/cLAvvehkpNx

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