从集合视图中拖动项目并放入其他视图IOS

Question

I have a collection view with some images. And I have another UIView. I want the image from the collection view to be dragged and drop into UIView such that on dropping on the UIView some action say colour changes. Also the image should remain in its original place after drop.

This is my code for the collection view.

-(UICollectionViewCell *) collectionView:(UICollectionView *)collectionView cellForItemAtIndexPath:(NSIndexPath *)indexPath{
UICollectionViewCell*aCell = [collectionView dequeueReusableCellWithReuseIdentifier:@"myCell" forIndexPath:indexPath];

UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(3,5,100,100)];
imgView.contentMode = UIViewContentModeScaleAspectFit;
imgView.clipsToBounds = YES;
imgView.image = [UIImage imageNamed: [imagePackArray objectAtIndex:indexPath.row]];
[aCell addSubview:imgView];
 aCell.backgroundColor = [UIColor redColor];
  return aCell;

}

I tried panning gesture to implement this however was unsuccessful.

- (IBAction)handlePan:(UIPanGestureRecognizer *)sender {
NSLog(@"panning");
CGPoint translation = [sender translationInView:self.view];
sender.view.center = CGPointMake(sender.view.center.x + translation.x,
                                     sender.view.center.y + translation.y);
[sender setTranslation:CGPointMake(0, 0) inView:self.view];

}

Please see the screen shot. I want to drag the image from the collection view to the cart image (which is in the UIView)

What approach should I take? Can someone guide me or provide code snippets/links which can help?

Answer 1

I found a library by Markus Gasser . You can find it below:

On Github (authoritative): https://github.com/frenetisch-applaudierend/ios-drag-and-drop or On Bitbucket: https://bitbucket.org/foensi/ios-drag-and-drop

It's a very clean library that comes with a sample app. It shows how you can move views from one stack to another; all nicely animated.

Caveat: Using with UICollectionView

I've tried it out with CollectionViews: if you register the whole view as a dragSource (which the demo shows), I found that you can no longer scroll the content. This is because the drag-and-drop controller's gesture recogniser captures all gesture events and does not pass it through to the underlying UICollectionView .

I asked the author about this, and he had this to say:

I meant to implement a mechanism to provide a different gesture recognizer for dragging, but I never really needed it in my projects. What I'm currently doing in this situation is to define only a subview of the UICollectionViewCell as the drag source. So if the user scrolls over the collection view it'll still work, but dragging from let's say the cell's icon will start drag and drop. Another possible way would be to set a delegate to the UICollectionView panGestureRecognizer and implement -gestureRecognizer:shouldBeRequiredToFailByGestureRecognizer: to fail on other pan recognizers (though I never used this).

So all in all very useful — but I've still got to work out how to make scrolling work.