Drag and drop

[PureWeen]

Description of Change

Preview release of Drag and Drop

FYI only works on iOS11+ because that's when the drag and drop apis were added

Issues Resolved

• fixes [Spec] DragGestureRecognizer DropGestureRecognizer  #10778

API Changes

DropGestureRecognizer

public class DropGestureRecognizer
{
     public bool AllowDrop;
     public DragEventArgs DragOver;
     public ICommand DragOverCommand;
     public object DragOverCommandParameter;

     public DropEventArgs Drop;
     public ICommand DropCommand;
     public object DropCommandParameter;

}

DragGestureRecognizer

public class DragGestureRecognizer
{
     public bool CanDrag;
     public DropCompletedEventArgs DropCompleted;
     public ICommand DropCompletedCommand;
     public object DropCompletedCommandParameter;

     public DragItemsStartingEventArgs DragStarting;
     public ICommand DragStartingCommand;
     public object DragStartingCommandParameter;
}

DragItemsStartingEventArgs

public class DragItemsStartingEventArgs
{
     bool Cancel;
     DataPackage Data;
}

DataPackageOperation

[Flags]
public enum DataPackageOperation
{
     None, Copy
}

DragEventArgs

public class DragEventArgs
{
     DataPackage Data;
     DataPackageOperation AcceptedOperation
}

DropCompletedEventArgs

public class DropCompletedEventArgs
{
}

DropEventArgs

public class DropEventArgs
{
     DataPackageView Data;
     bool Handled;
}

DataPackage

This is used to setup the data for transfer

public class DataPackage
{
     public ImageSource Image {Get;set;}
     public string Text;
     public DataPackageView View
}

DataPackageView

This is a read-only copy of the DataPackage object.
This is all the user gets on the drop event to retrieve the data. They can't modify the package

public class DataPackageView
{
     public ImageSource GetImageAsync();
     public string GetTextAsync();
}

Platforms Affected

• Core/XAML (all platforms)
• iOS 11+
• Android
• UWP

Testing Procedure

• Galleries Tests Provided

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)

[rmarinho]

Testing a comment

[samhouts]

Should you have a null image source? No. Was it the first thing I tried? Yes.

        <Image x:Name="Image" Margin="10,292,10,0" HeightRequest="338" BackgroundColor="Aqua">
            <Image.GestureRecognizers>
                <DragGestureRecognizer CanDrag="True"></DragGestureRecognizer>
            </Image.GestureRecognizers>
        </Image>

	at Xamarin.Forms.Platform.Android.DragAndDropGestureHandler.ConvertToClipDataItem (Xamarin.Forms.ImageSource source, System.Collections.Generic.List`1[T] mimeTypes) [0x0008a] in D:\agent\1\s\Xamarin.Forms.Platform.Android\DragAndDropGestureHandler.cs:321
	at Xamarin.Forms.Platform.Android.DragAndDropGestureHandler+<>c__DisplayClass18_0.<OnLongPress>b__0 (Xamarin.Forms.DragGestureRecognizer rec) [0x000dd] in D:\agent\1\s\Xamarin.Forms.Platform.Android\DragAndDropGestureHandler.cs:245
	at Xamarin.Forms.Platform.Android.DragAndDropGestureHandler.SendEventArgs[TRecognizer] (System.Action`1[T] func, Xamarin.Forms.View view) [0x00066] in D:\agent\1\s\Xamarin.Forms.Platform.Android\DragAndDropGestureHandler.cs:113
	at Xamarin.Forms.Platform.Android.DragAndDropGestureHandler.OnLongPress (Android.Views.MotionEvent e) [0x00028] in D:\agent\1\s\Xamarin.Forms.Platform.Android\DragAndDropGestureHandler.cs:218
	at Xamarin.Forms.Platform.Android.InnerGestureListener.Android.Views.GestureDetector.IOnGestureListener.OnLongPress (Android.Views.MotionEvent e) [0x00009] in D:\agent\1\s\Xamarin.Forms.Platform.Android\InnerGestureListener.cs:120
	at Android.Views.GestureDetector+IOnGestureListenerInvoker.n_OnLongPress_Landroid_view_MotionEvent_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_e) [0x0000f] in <a522ecdee49144d0b8411a1cab7b9ada>:0
	at at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.49(intptr,intptr,intptr) in :0```

[samhouts]

HotPotato.zip

Works great on Android.
Doesn't seem to work at all on iOS.
UWP just crashes for me, but that's another story.

[BurkusCat]

@PureWeen I really like this API. I've been using it a little bit on UWP and it seems very solid :) (I've posted one issue around the UWP cursor and a docs issue around how to use commands but other than that it is pretty great!)