How do I implement dragging of an NSImage inside of an NSView?

Question

I've never dealt much with NSViews so I am at a loss on this. I have a custom class that contains an NSImage ivar. I also have a subclass of NSView that contains an array of instances of my custom class. The NSImage from the custom class gets drawn at the center of the NSView upon creation. I need to be able to drag that NSImage around the NSView freely.

I have implemented the following methods to get started:

-(void)mouseDown:(NSEvent *)theEvent
{
    [self beginDraggingSessionWithItems: /* I don't know what to put here */
                                  event:theEvent
                                 source:self];
}

I have tried placing the NSImage object from my custom class in an array as the item to drag but an exception is raised. I also tried creating an NSDraggingItem to place in there but it could not write the object to the pasteboard and raised an exception.

-(void)draggingSession:(NSDraggingSession *)session willBeginAtPoint:(NSPoint)screenPoint
{
    NSLog(@"began");
}

-(void)draggingSession:(NSDraggingSession *)session movedToPoint:(NSPoint)screenPoint
{
    NSLog(@"moved");
}

-(void)draggingSession:(NSDraggingSession *)session endedAtPoint:(NSPoint)screenPoint operation:(NSDragOperation)operation
{
    NSLog(@"ended");
}

These methods get called properly as I click and drag my mouse around my subclass of NSView however they are useless until I can get the object to move.

I believe the answer may be to create an NSDraggingItem for each image and use that to move them freely around the view however I could not get it to work with even one object and do not know how to properly implement this idea. Any help is appreciated.

score 0 · Accepted Answer · answered May 12 '13 at 16:26

Went through a lot of headache on this one but finally figured it out. Instead of using beginDraggingSessionWithItems:event:source I used dragImage:at:offset:event:pasteboard:source:slideBack:. I keep track of the coordinates of each image in the view and can tell whether a specific image was clicked on or not by utilizing the following method I wrote in mouseDown:

-(BOOL)clickedAtPoint:(NSPoint)point InsideRect:(NSRect)rect
{
    if ((point.x < (rect.origin.x + rect.size.width) &&
        point.y < (rect.origin.y + rect.size.height)) &&
        point.x > rect.origin.x && point.y > rect.origin.y) {
            return YES;
        }
    return NO;
}

`dragImage:at:offset:event:pasteboard:source:slideBack:` is deprecated as of 10.10 SDK. — Boris Dušek, Jul 07 '14 at 06:55

How do I implement dragging of an NSImage inside of an NSView?

1 Answers1