macos - NSCollectionView 拖放示例

Question

我正在尝试在 NSCollectionView 中实现拖放，这将允许重新排列 View 中的单元格。我已经设置了委托(delegate)并实现了以下方法:

-(BOOL)collectionView:(NSCollectionView *)collectionView writeItemsAtIndexes:(NSIndexSet *)indexes toPasteboard:(NSPasteboard *)pasteboard {
    NSLog(@"Write Items at indexes : %@", indexes);
    return YES;
}

- (BOOL)collectionView:(NSCollectionView *)collectionView canDragItemsAtIndexes:(NSIndexSet *)indexes withEvent:(NSEvent *)event {
    NSLog(@"Can Drag");
    return YES;
}

- (BOOL)collectionView:(NSCollectionView *)collectionView acceptDrop:(id<NSDraggingInfo>)draggingInfo index:(NSInteger)index dropOperation:(NSCollectionViewDropOperation)dropOperation {
    NSLog(@"Accept Drop");
    return YES;
}

-(NSDragOperation)collectionView:(NSCollectionView *)collectionView validateDrop:(id<NSDraggingInfo>)draggingInfo proposedIndex:(NSInteger *)proposedDropIndex dropOperation:(NSCollectionViewDropOperation *)proposedDropOperation {
    NSLog(@"Validate Drop");
    return NSDragOperationMove;
}

我不知道如何进一步解决这个问题。有了这个，我可以看到现在我可以拖动单个集合项，但是如何制作 Drop ？

Answer 1

您只实现了委托(delegate)方法，但某些方法没有逻辑。例如，要拖动集合项，我将添加以下逻辑:

-(BOOL)collectionView:(NSCollectionView *)collectionView writeItemsAtIndexes:(NSIndexSet *)indexes toPasteboard:(NSPasteboard *)pasteboard {
    NSData *indexData = [NSKeyedArchiver archivedDataWithRootObject:indexes];
    [pasteboard setDraggedTypes:@[@"my_drag_type_id"]];
    [pasteboard setData:indexData forType:@"my_drag_type_id"];
    // Here we temporarily store the index of the Cell, 
    // being dragged to pasteboard.
    return YES;
}

- (BOOL)collectionView:(NSCollectionView *)collectionView acceptDrop:(id<NSDraggingInfo>)draggingInfo index:(NSInteger)index dropOperation:(NSCollectionViewDropOperation)dropOperation {
    NSPasteboard *pBoard = [draggingInfo draggingPasteboard];
    NSData *indexData = [pBoard dataForType:@"my_drag_type_id"];
    NSIndexSet *indexes = [NSKeyedUnarchiver unarchiveObjectWithData:indexData];
    NSInteger draggedCell = [indexes firstIndex];
    // Now we know the Original Index (draggedCell) and the 
    // index of destination (index). Simply swap them in the collection view array.
    return YES;
}

您还需要将 Collection View 注册为awakefromnib中的拖动类型

[_myCollectionView registerForDraggedTypes:@[@"my_drag_type_id"]];

并确保您已将 Collection View 设置为可选择。