1 Reply
      Latest reply on Apr 30, 2019 11:58 AM by jfahrenkrug
      DevFelix Level 1 Level 1 (0 points)

        Before iOS 12.2 we used the following code to implement our own handling for a UIDropInteraction. However, this functionality is broken on iOS 12.2, we no longer can find a view (or subview) of wkwebview where we can add our own UIDropInteraction.


        UIView *dropInteractionContainingView = nil;
        UIDropInteraction *defaultDropInteractionToRemove = nil;
        for (UIView *subview in self.webview.scrollView.subviews) {
            for (id<UIInteraction> interaction in subview.interactions) {
                if ([interaction isKindOfClass:[UIDropInteraction class]]) {
                    dropInteractionContainingView = subview;
                    defaultDropInteractionToRemove = interaction;
                //on iOS 12.2 these two variables are always nil.
        if (dropInteractionContainingView != nil && defaultDropInteractionToRemove != nil) {
            //Now we replace the existing unwanted uidropinteraction with our own, custom implementation.
            UIDropInteraction *customDropInteraction = [[UIDropInteraction alloc] initWithDelegate:self];
            [dropInteractionContainingView removeInteraction:defaultDropInteractionToRemove];
            [dropInteractionContainingView addInteraction:customDropInteraction];


        Any ideas how to fix this in iOS 12.2?

        • Re: WKWebview: UIDropInteraction is broken on iOS 12.2
          jfahrenkrug Level 1 Level 1 (0 points)

          This is a great question and I just debugged this myself. Here's what's different in iOS 12.2: The UIDragInteraction is only added _after_ the WKContentView is added to a _window_ (not just a superview).


          Here's how I found it:

          I searched through the WebKit source and found this: https://github.com/WebKit/webkit/blob/65619d485251a3ffd87b48ab29b342956f3dcdc7/Source/WebKit/UIProcess/ios/WKContentViewInteraction.mm#L4953

          That's the method that creates and adds the UIDragInteraction. It turns out that this method (setupDataInteractionDelegates) actually exists on WKContentView. So I set a symbolic breakpoint on "-[WKContentView setupDataInteractionDelegates]". Sure enough that breakpoint was hit. I then displayed the backtrace in lldb:


          (lldb) bt
          * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 50.1
            * frame #0: 0x00000001115b726c WebKit`-[WKContentView(WKInteraction) setupDataInteractionDelegates]
              frame #1: 0x00000001115a8852 WebKit`-[WKContentView(WKInteraction) setupInteraction] + 1026
              frame #2: 0x00000001115a5155 WebKit`-[WKContentView didMoveToWindow] + 79


          So we see that the interactions are only added AFTER the view is added to a view hierarchy that is attached to a window. Your old code should work, as long as you only call it after the WKWebView has been added to a window.