UIDragInteraction拖拽UIDropInterac

if (IOS11) {
UIDragInteraction* drag = [[UIDragInteraction alloc] initWithDelegate:self];
[self addInteraction:drag];
self.userInteractionEnabled = true;
}
**************代理
API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @protocol UIDragInteractionDelegate <NSObject>
@required
//提供数据源 长按UI开始拖拽

• (NSArray<UIDragItem *> *)dragInteraction:(UIDragInteraction *)interaction itemsForBeginningSession:(id<UIDragSession>)session;
  @optional
  //提供UITargetedDragPreview的相关信息 长按UI是有个lift（UI举起效果，系统自动生成）
  //返回nil 没有效果； 不实现该方法 interaction.view自动生成UITargetedDragPreview
• (nullable UITargetedDragPreview *)dragInteraction:(UIDragInteraction *)interaction previewForLiftingItem:(UIDragItem *)item session:(id<UIDragSession>)session;
  //drag发生时调用
• (void)dragInteraction:(UIDragInteraction *)interaction willAnimateLiftWithAnimator:(id<UIDragAnimating>)animator session:(id<UIDragSession>)session;
  //将要开始drag
• (void)dragInteraction:(UIDragInteraction *)interaction sessionWillBegin:(id<UIDragSession>)session;
  //是否允许数据移动 app内移动有效，跨app总是复制数据
• (BOOL)dragInteraction:(UIDragInteraction *)interaction sessionAllowsMoveOperation:(id<UIDragSession>)session;
  //是否允许跨应用程序进行drag ipad
• (BOOL)dragInteraction:(UIDragInteraction *)interaction sessionIsRestrictedToDraggingApplication:(id<UIDragSession>)session;
  //设置预览视图是否显示原始大小
• (BOOL)dragInteraction:(UIDragInteraction *)interaction prefersFullSizePreviewsForSession:(id<UIDragSession>)session;
  //已经结束移动
• (void)dragInteraction:(UIDragInteraction *)interaction sessionDidMove:(id<UIDragSession>)session;
  //drag将要结束时调用
• (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session willEndWithOperation:(UIDropOperation)operation;
  //drag已经结束时调用
• (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session didEndWithOperation:(UIDropOperation)operation;
  //拖拽源进行了放置操作后调用
• (void)dragInteraction:(UIDragInteraction *)interaction sessionDidTransferItems:(id<UIDragSession>)session;
  //设置是否允许向拖拽中的项目添加数据 返回数据载体数组 drag时点击拖拽的组件调用
• (NSArray<UIDragItem *> *)dragInteraction:(UIDragInteraction *)interaction itemsForAddingToSession:(id<UIDragSession>)session withTouchAtPoint:(CGPoint)point;
  //设置允许进行拖拽中追加数据的拖拽行为会话
• (nullable id<UIDragSession>)dragInteraction:(UIDragInteraction *)interaction sessionForAddingItems:(NSArray<id<UIDragSession>> *)sessions withTouchAtPoint:(CGPoint)point;
  //将要向拖拽组件中追加数据时调用
• (void)dragInteraction:(UIDragInteraction *)interaction session:(id<UIDragSession>)session willAddItems:(NSArray<UIDragItem *> *)items forInteraction:(UIDragInteraction *)addingInteraction;
  //设置拖拽动作取消的视图动画 返回nil则消除动画
• (nullable UITargetedDragPreview *)dragInteraction:(UIDragInteraction *)interaction previewForCancellingItem:(UIDragItem *)item withDefault:(UITargetedDragPreview *)defaultPreview;
  //drag动画将要取消时调用
• (void)dragInteraction:(UIDragInteraction *)interaction item:(UIDragItem *)item willAnimateCancelWithAnimator:(id<UIDragAnimating>)animator;

API_AVAILABLE(ios(11.0)) API_UNAVAILABLE(watchos, tvos) @protocol UIDropInteractionDelegate <NSObject>

@optional
//是否可以处理来自Drag的数据

• (BOOL)dropInteraction:(UIDropInteraction *)interaction canHandleSession:(id<UIDropSession>)session;
  //Drag的UI元素进入Drop的区域
• (void)dropInteraction:(UIDropInteraction *)interaction sessionDidEnter:(id<UIDropSession>)session;
  //第二次判断是否可以接收 无法接收用UIDropOperationCancel
• (UIDropProposal *)dropInteraction:(UIDropInteraction *)interaction sessionDidUpdate:(id<UIDropSession>)session;
  //Drag的UI元素离开Drop的区域
• (void)dropInteraction:(UIDropInteraction *)interaction sessionDidExit:(id<UIDropSession>)session;
  //取出来自drag的数据
  1
  NSLog(@"%f,%f",[session locationInView:self.view].x,[session locationInView:self.view].y)
• (void)dropInteraction:(UIDropInteraction *)interaction performDrop:(id<UIDropSession>)session;
  //drop结束
• (void)dropInteraction:(UIDropInteraction *)interaction concludeDrop:(id<UIDropSession>)session;
  //整个Drag和Drop结束
• (void)dropInteraction:(UIDropInteraction *)interaction sessionDidEnd:(id<UIDropSession>)session;
  //手指松开，控制Drag Preview 如何自然的过渡到Drop之后的Preview
• (nullable UITargetedDragPreview *)dropInteraction:(UIDropInteraction *)interaction previewForDroppingItem:(UIDragItem *)item withDefault:(UITargetedDragPreview *)defaultPreview;
  //手指松开Drop时，控制Drop区域的其他UI元素如何展示动画
• (void)dropInteraction:(UIDropInteraction *)interaction item:(UIDragItem *)item willAnimateDropWithAnimator:(id<UIDragAnimating>)animator;