正常模式 / Normal Mode:

• 不拦截子部件的手势事件
• Do not intercept the GestureDetector events of the child widget
• 不能拖动和删除子部件
• Can't drag and delete the children widget

编辑模式 / Draggable mode:

• 长按子部件进入编辑模式
• Long press the children widget to enter the draggable mode
• 进入编辑模式后，不再需要长按来拖动子部件，直接拖动就可以了
• In the draggable mode, do not need to long press to drag the children widget, just drag it.
• 在可删除子部件上显示删除按钮
• Show the delete button on the deletable child widget
• 拦截可拖动可删除的子部件的手势事件
• Intercept the GestureDetector events of the draggable and deletable child widget
• 可以拖动和删除子部件
• Can drag and delete the children widget
• 返回键 退出编辑模式
• Press the Back key to exit the draggable mode.

事件 / Events

• onChanged(List<T> items)
  • 当子项目改变时触发(拖动过后，删除后)
  • Trigger when the items changed(dragged, deleted)
• onDraggableModeChanged(bool mode)
  • mode为true则进入了编辑模式，为false则退出了编辑模式.
  • When mode is true then in the draggable mode. If false it mean exited the draggable mode.
• Future<bool> onBeforeDelete(int index, T item)
  • 删除item的确认事件，返回true删除，返回false不删除
  • The event for confirm to delete a item, if return true then delete, if false then no action.

DraggableContainerState的方法 / The DraggableContainerState methods:

• Future<void> addSlot({T item, bool triggerEvent: true})

  • 添加一个新的槽。
  • Add a new slot.

• Future<void> addSlots(int count, {bool triggerEvent: true})

  • 添加多个槽，用对应数量的null填充
  • Add multiple slots and fill with null.

• Future<T> popSlot()

  • 移除最后一个槽位，返回对应的item
  • Remove the last slot and return the item.

• findSlot(Offset position)

  • 根据坐标寻找槽
  • find the slot use Offset position.

• T getItem(int index)

  • 使用index获取item，空的槽item为null
  • Use index get item, the empty slot's item is null.

• bool insteadOfIndex(int index, T item, {bool triggerEvent: true, bool force: false})

  • 使用item替换到index的位置
  • Use item to instead of the index position.

• bool moveTo(int from, int to, {bool triggerEvent: true, bool force: false})

  • 将item从from移动到to
  • Move the item from the 'from' index to the 'to' index.

• bool removeItem(T item, {bool triggerEvent: true})

  • 根据item删除item
  • Delete item according to item

• bool removeIndex(int index, {bool triggerEvent: true})

  • 删除index位置的item
  • Delete item from the index position.

• bool addItem(T item, {bool triggerEvent: true})

  • 添加item，永远添加到第一个null的位置，找不到null则返回false代表添加失败
  • Add item, always add to the first null position, if can't find null, return false it mean to add failure.

关于上文提到的参数 / About the Parameters:

• bool triggerEvent:
  • 是否触发onChanged事件
  • Trigger the onChanged event or not
• bool force:
  • 如果目标item的deletable为false，则强制覆盖
  • Forced override if the target item's deleteable is false