Скачать или смотреть How to Prevent OnMouseEnter() and OnMouseExit() from Interfering with OnMouseDrag() in Unity

Discover how you can avoid the repeated calls of `OnMouseEnter()` and `OnMouseExit()` while dragging objects in Unity. Learn simple workarounds to improve your game logic!
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This video is based on the question https://stackoverflow.com/q/73792116/ asked by the user 'Ahri' ( https://stackoverflow.com/u/20046154/ ) and on the answer https://stackoverflow.com/a/73796536/ provided by the user 'Nikolai' ( https://stackoverflow.com/u/10699097/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding the OnMouseEnter() and OnMouseExit() Issue in Unity

If you're developing a game in Unity, you may encounter a frustrating issue where the methods OnMouseEnter() and OnMouseExit() are called repeatedly while you're dragging an object with OnMouseDrag(). This is particularly annoying, as it can lead to unexpected changes in your object's appearance and behavior, especially when the mouse is moved quickly.

The Problem Explained

When you drag an object with the mouse, you'd expect that as long as the object is being dragged, it wouldn't trigger the enter and exit events. However, the Unity event system processes these methods in a sequence that can lead to confusion. Here's how it works:

Mouse Movement: As you move your mouse, Unity determines that the position has changed.

Exit Detection: If you're moving your mouse fast enough, Unity may register that the mouse has exited the object, leading to the call of OnMouseExit().

Drag Event: After exiting detection, Unity processes the dragging event and calls OnMouseDrag(), moving the object to the new mouse position.

Enter Detection: Due to the object's new position, Unity checks again and finds the mouse is now over the object, calling OnMouseEnter().

This cycle continues, especially if you move your mouse quickly, which can create a visually jarring effect where an object constantly switches between red and white colors, and corresponding debug messages flood the console.

A Possible Solution: Custom Dragging Logic

To prevent OnMouseEnter() and OnMouseExit() from interfering during a drag action, you can implement your own dragging logic with state management. Below, we outline a clean and straightforward method using flags to manage mouse hover and drag states.

Step-by-Step Implementation

Create a New Script: Replace your existing dragging logic with the following example, which includes custom hover and drag states.

[[See Video to Reveal this Text or Code Snippet]]

Key Changes & Benefits

State Management: The use of _hovered and _dragged flags distinguishes whether the object is under mouse hover or being dragged. This separates the logic for enter and exit method calls.

Controlled Exit Handling: The OnMouseExit() function only sets the hover state to false if the object isn’t being dragged, preventing premature exit handling.

Improved Visual Feedback: Your game's visuals will be consistent, providing a smoother player experience with fewer jarring color changes.

Conclusion

By implementing your own drag logic, you can gain complete control over the behavior of your Unity objects during user interactions. This avoids the annoying issues linked to swift mouse movements triggering OnMouseEnter() and OnMouseExit() during drag actions.

Implement these changes for a more robust and user-friendly game experience!