I have an app (on MacOS) that I am moving to IOS. The app needs to read and write external data files that are in the “Files” folder in the device. I have added a picker of class UIDocumentPickerMBS but I can not connect the results of the “documentPickerDidPickDocuments” event handler back to the app with the picker.
Does anyone have advice or an example of using UIDocumentPickerMBS to access an external data file from the app. I need to connect the picker event to the app, but I don’t see how to do this. I think this is a structural problem regarding the sandboxing, and I have failed so far.
Thanks for any help or examples (beyond the MBS example “Document Picker iOS” project, which does not show how to access data in the selected file).
Well, if you subclass UIDocumentPickerMBS to get the events implemented, you could keep a property with the reference back to the caller there.
Alternatively you can use AddHandler within the screen you are in.
So here this variant:
Sub Pressed() Handles Pressed
table1.RemoveAllRows
OpenButton.Enabled = False
ExportButton.Enabled = False
Var types() As String
types.append "image/jpeg"
types.append ".txt"
types.append "com.adobe.pdf"
Var asCopy As Boolean = True
picker = New UIDocumentPickerMBS(UIDocumentPicker.ModeOpen, types, asCopy)
AddHandler picker.documentPickerDidPickDocuments, AddressOf documentPickerDidPickDocuments
AddHandler picker.documentPickerWasCancelled, AddressOf documentPickerWasCancelled
picker.Present
End Sub
and you add two methods to your screen:
Public Sub documentPickerDidPickDocuments(picker as UIDocumentPickerMBS, URLs() as String)
If picker.documentPickerMode = picker.ModeExportToService Then
MessageBox "Exported."
Else // import/open
For Each url As String In urls
Var file as new FolderItem(url, FolderItem.PathModes.URL)
Table1.AddRow file.DisplayName
Next
end if
OpenButton.Enabled = True
ExportButton.Enabled = True
End Sub
and a method for cancel:
Public Sub documentPickerWasCancelled(picker as UIDocumentPickerMBS)
OpenButton.Enabled = True
ExportButton.Enabled = true
End Sub
this way you get the event directly inside the screen where you calk it from. No subclass needed.
I have finally figured out my problem, which was due mainly to my being new to IOS.
Thanks to those who replied with help, especially Christian and the MBS team, who sent several solutions.
As a newcomer to IOS Xojo programming, I did not understand several terms, and did not understand the central importance of the term “Screen”. The example “Document Picker iOS.xojo_binary_project” did in fact have the answer for me, but it took some time for me to understand. An important lesson learned.
When I moved my working app to IOS from MacOS, I had not studied the differences, hoping to be able to find examples to get me going.
It took me a while to understand in the MBS example (“Document Picker iOS”) that the Property ‘screen’ with Type ‘MainScreen’ made screen inherit the class ‘MainScreen’. This was how to use a subclass within the picker that permits accessing properties (variables in my case) of the main app. This is the connection that I was missing between the picker event handler and variables in the main app. The picker allows me to access the external data file and bring the data values into the variables by referencing ‘screen.variablename’. This is all basic stuff, of course, but it took some time, and several failed attempts, before I made the connection with the example.
Now I discover the 'IOS Guide" in xojo.helpdocsonline.com/, a resource that would have helped before I started the migration and which I will consult in the future.
I am an ancient programmer, 82 yo, who started with Fortran around 1964, now in too much of a hurry.
).