Fixing Draggable Event Position In React Native Calendar Kit

Are you experiencing issues with draggable events appearing in the wrong position when using React Native Calendar Kit with multiple resources and resource scrolling? You're not alone! This article dives into a common problem encountered when implementing custom draggable events in a multi-resource calendar environment. We'll explore the bug, its causes, and provide a step-by-step guide to reproduce and potentially resolve the issue.

Understanding the Draggable Event Position Bug

When working with React Native Calendar Kit, a powerful library for creating calendar interfaces in React Native applications, you might encounter a peculiar bug. This issue arises specifically when you have multiple resources, enable resource pagination and scrolling, and implement custom draggable events. The symptom? The draggable event, when dragged, appears shifted or misaligned from its original position. This can lead to a frustrating user experience, as the visual representation of the event doesn't accurately reflect its actual location on the calendar.

The core problem lies in how the library calculates the position of the draggable event relative to the calendar grid when resource scrolling is enabled. The library's internal logic might not be correctly accounting for the scrolling offset, resulting in the misalignment. This becomes particularly noticeable when the number of resources exceeds the resourcePerPage setting, triggering resource pagination and scrolling.

To truly understand the scope of this issue, let's break down the specific conditions that trigger it:

• Multiple Resources: The bug manifests when you have more resources than can be displayed on a single page, necessitating resource scrolling.
• Resource Pagination Enabled (resourcePagingEnabled={true}): Pagination divides the resources into pages, adding another layer of complexity to positioning.
• Resource Scrolling Enabled (enableResourceScroll={true}): This allows users to scroll through resources horizontally, which introduces an offset that needs to be considered.
• resourcePerPage: Setting this prop to a value lower than the total number of resources triggers pagination and scrolling, highlighting the bug.
• Custom Draggable Event (renderDraggableEvent): Using a custom component to render the draggable event seems to exacerbate the issue, suggesting a potential conflict with the library's internal positioning mechanisms.

The visual indicators of this bug are quite clear: the dragged event has a noticeable offset from its original slot on the calendar. In the provided example, the draggable event is styled with red borders to make this misalignment easily identifiable.

Reproducing the Issue: A Step-by-Step Guide

To better grasp the bug and potentially find a solution, it's crucial to be able to reproduce it consistently. Here's a detailed guide to replicate the draggable event position issue in React Native Calendar Kit:

1. Set up your resources: First, you need to define an array of resources. Ensure you have more resources than you intend to display per page. For instance:

const resources = [
  { id: 'room1', title: 'Meeting Room 1' },
  { id: 'room2', title: 'Meeting Room 2' },
  { id: 'room3', title: 'Conference Room' },
  { id: 'room4', title: 'Room 4' },
  { id: 'room5', title: 'Room 5' },
  { id: 'room6', title: 'Room 6' },
  { id: 'room7', title: 'Room 7' },
  { id: 'room8', title: 'Room 8' },
  { id: 'room9', title: 'Room 9' },
  { id: 'room10', title: 'Room 10' },
];

This creates ten different resources, simulating a scenario with multiple rooms or personnel.

2. Create an event: Next, define an event and associate it with a specific resource by mapping the resourceId to an existing resource id:

const now = new Date();

const events = [
  {
    id: 'event1',
    title: 'Event 1',
    start: { dateTime: now.toISOString() },
    end: { dateTime: new Date(new Date().setHours(now.getHours() + 1)).toISOString() },
    resourceId: 'room3',
  },
] satisfies EventItem[];

This code snippet creates a single event, "Event 1", scheduled for the current time and lasting for an hour. It's assigned to the resource with the ID `'room3'`. Make sure you import `EventItem` from the `react-native-calendar-kit` library.

3. Manage the selected event state: To handle drag interactions, you'll need to manage the state of the selected event:

 const [selectedEvent, setSelectedEvent] = React.useState<SelectedEventType | undefined>(
    undefined
  );

This initializes a state variable `selectedEvent` to `undefined`, which will hold the currently selected event during drag operations. Also make sure you import `SelectedEventType` from the `react-native-calendar-kit` library.

4. Implement a drag end handler: Create a function to clear the selectedEvent state when a drag operation ends:

 const handleDragEnd = React.useCallback(() => {
    setSelectedEvent(undefined); // Clear the selected event after editing
  }, []);

This `handleDragEnd` function is crucial for resetting the state after a drag, ensuring proper behavior for subsequent interactions.

5. Define a custom draggable event renderer: This is where you'll customize the appearance of the draggable event. The provided example adds red borders to make the misalignment more visible:

  const renderDraggableEvent = React.useCallback(
    (props: DraggableEventProps) => (
      <DraggableEvent
        {...props}
        TopEdgeComponent={
          <View
            style={{
              height: 15,
              backgroundColor: 'red',
              position: 'absolute',
              width: '100%',
            }}>
            <Text style={{ textAlign: 'center', fontSize: 10 }}>Drag</Text>
          </View>
        }
        BottomEdgeComponent={
          <View
            style={{
              height: 15,
              backgroundColor: 'red',
              position: 'absolute',
              bottom: 0,
              width: '100%',
            }}>
            <Text style={{ textAlign: 'center', fontSize: 10 }}>Drag</Text>
          </View>
        }
      />
    ),
    []
  );

This `renderDraggableEvent` function takes `DraggableEventProps` as input and returns a custom `DraggableEvent` component. The `TopEdgeComponent` and `BottomEdgeComponent` are styled with red backgrounds to highlight the positioning issue. Don't forget to import `DraggableEventProps` and `DraggableEvent` from the `react-native-calendar-kit` library.

6. Configure the CalendarContainer and CalendarBody: Finally, integrate all the components and props into your CalendarContainer and CalendarBody:

    <CalendarContainer
        events={events}
        resources={resources}
        resourcePerPage={5}
        resourcePagingEnabled={true}
        enableResourceScroll={true}
        selectedEvent={selectedEvent}
        onLongPressEvent={setSelectedEvent}
        allowDragToEdit={true}
        allowDragToCreate={true}
        onDragSelectedEventEnd={handleDragEnd}>
        <CalendarHeader />
        <CalendarBody renderDraggableEvent={renderDraggableEvent} />
      </CalendarContainer>

Here's a breakdown of the key props:
*   `events`: The array of events to display.
*   `resources`: The array of resources.
*   `resourcePerPage`: Limits the number of resources displayed per page to 5.
*   `resourcePagingEnabled`: Enables pagination for resources.
*   `enableResourceScroll`: Allows horizontal scrolling of resources.
*   `selectedEvent`: The currently selected event for dragging.
*   `onLongPressEvent`: Sets the selected event on a long press.
*   `allowDragToEdit`: Enables event dragging for editing.
*   `allowDragToCreate`: Enables event creation via dragging.
*   `onDragSelectedEventEnd`: Calls `handleDragEnd` when a drag operation finishes.
*   `renderDraggableEvent`: Uses the custom `renderDraggableEvent` function.

7. Observe the Misalignment: With this setup, long-press and drag an event. You should observe that the custom draggable event shifts to the left of the original event position, confirming the bug.

By following these steps, you can consistently reproduce the issue and have a solid foundation for testing potential solutions.

Analyzing the Root Cause

To effectively address the draggable event position bug, it's essential to delve into its underlying cause. The issue seems to stem from the interaction between resource scrolling, pagination, and the custom draggable event rendering. Here's a breakdown of the potential contributing factors:

• Scroll Offset Calculation: The core problem likely lies in how the CalendarContainer or CalendarBody calculates the position of the draggable event when resource scrolling is enabled. The horizontal scroll offset, representing the distance the resource list has been scrolled, might not be correctly factored into the event's positioning.
• Pagination and Resource Mapping: When resourcePagingEnabled is set to true, the resources are divided into pages. The library needs to accurately map the event's resourceId to the correct position within the currently visible page. If this mapping is flawed, the event will appear in the wrong column.
• Custom Draggable Event Component: The use of a custom renderDraggableEvent function might introduce complexities. The library's internal drag handling logic might not be fully compatible with custom rendering, leading to positioning discrepancies. It's possible that the custom component's styling or layout is interfering with the library's calculations.
• Asynchronous Updates: There might be asynchronous updates within the calendar component that affect the layout. If the draggable event's position is calculated before these updates are complete, it could result in misalignment.

To confirm these hypotheses, you would need to dive into the source code of React Native Calendar Kit, specifically the CalendarContainer, CalendarBody, and DraggableEvent components. Pay close attention to the following:

• Event Positioning Logic: Examine how the library calculates the x and y coordinates of the draggable event based on its start and end times, resource ID, and scroll offset.
• Resource Mapping: Analyze how the library maps the resourceId to the corresponding column in the calendar grid, especially when pagination is enabled.
• Drag Handling: Investigate the drag handling logic within the DraggableEvent component and how it interacts with the calendar's layout.

By carefully dissecting these aspects of the code, you can gain a deeper understanding of the bug's root cause and identify potential areas for modification.

Potential Solutions and Workarounds

While a definitive solution might require changes to the React Native Calendar Kit library itself, there are several potential workarounds and approaches you can try to mitigate the issue:

1. Adjusting Scroll Offset: The most direct approach is to manually adjust the position of the draggable event to account for the scroll offset. This would involve:

   • Accessing the current scroll offset of the resource list.
   • Calculating the difference between the event's intended position and its actual position.
   • Applying a translation to the draggable event's style to correct the misalignment.

   This approach requires a good understanding of the calendar's layout and how the scroll offset is managed. You might need to use the onScroll event of the resource list to track the scroll offset and update the event's position accordingly.

2. Modifying Custom Draggable Event: If the custom renderDraggableEvent function is contributing to the issue, try simplifying it or adjusting its styling. You could try:

   • Removing any custom styling that might interfere with the library's layout.
   • Using the default DraggableEvent component provided by the library as a baseline.
   • Adding logging statements to the custom component to inspect its props and styling during a drag operation.

   By isolating the custom component, you can determine if it's the source of the problem or if the issue lies elsewhere.

3. Disabling Resource Scrolling or Pagination: As a temporary workaround, you could try disabling resource scrolling or pagination. This would eliminate the scroll offset issue but might not be a viable long-term solution if you need these features. If disabling resource scrolling resolves the issue, it further points to the scroll offset calculation as the primary culprit.

4. Exploring Alternative Calendar Libraries: If the issue proves too difficult to resolve, you might consider exploring alternative React Native calendar libraries. There are several other options available, each with its own strengths and weaknesses. However, switching libraries can be a significant undertaking, so it should be considered as a last resort.

It's important to note that these are just potential workarounds, and the effectiveness of each approach might vary depending on your specific implementation. Thorough testing is crucial to ensure that any solution you implement correctly addresses the issue without introducing new problems.

Contributing to React Native Calendar Kit

If you've identified a potential solution or have a deeper understanding of the bug's root cause, consider contributing back to the React Native Calendar Kit community. You can:

• Submit a pull request: If you have a fix, create a pull request with your proposed changes. Be sure to include a clear description of the issue, the solution, and any testing you've performed.
• Open an issue: If you don't have a fix but have valuable insights, open a new issue on the library's GitHub repository. Provide as much detail as possible, including steps to reproduce the issue, your environment information, and any observations you've made.
• Participate in discussions: Engage in existing discussions related to the bug. Sharing your experiences and ideas can help the community collectively find a solution.

By contributing to the library, you can help improve it for everyone and ensure that other developers don't encounter the same issues.

Conclusion

The draggable event position bug in React Native Calendar Kit with multiple resources and resource scrolling is a challenging issue, but by understanding its causes and exploring potential solutions, you can mitigate its impact on your application. Remember to thoroughly test any workarounds you implement and consider contributing back to the library to help the community.

For further exploration and a deeper dive into React Native Calendar Kit, check out the official React Native Calendar Kit Documentation.