虚拟摇杆在移动游戏开发中，是很常见的需求，今天我们在Unity中，使用UGUI来实现一个简单的虚拟摇杆功能。

1.打开Unity，新创建一个UIJoystick.cs脚本，代码如下：

using UnityEngine;using UnityEngine.EventSystems; public class UIJoystick : MonoBehaviour, IDragHandler, IEndDragHandler{ /// <summary> /// 被用户拖动的操纵杆 /// </summary> public Transform target; /// <summary> /// 操纵杆可移动的最大半径 /// </summary> public float radius = 50f; /// <summary> /// 当前操纵杆在2D空间的x,y位置 /// 摇杆按钮的值【-1，1】之间 /// </summary> public Vector2 position; //操纵杆的RectTransform组件 private RectTransform thumb; void Start() { thumb = target.GetComponent<RectTransform>(); } /// <summary> /// 当操纵杆被拖动时触发 /// </summary> public void OnDrag(PointerEventData data) { //获取摇杆的RectTransform组件，以检测操纵杆是否在摇杆内移动 RectTransform draggingPlane = transform as RectTransform; Vector3 mousePos; //检查拖动的位置是否在拖动rect内， //然后设置全局鼠标位置并将其分配给操纵杆 if (RectTransformUtility.ScreenPointToWorldPointInRectangle (draggingPlane, data.position, data.pressEventCamera, out mousePos)) { thumb.position = mousePos; } //触摸向量的长度（大小） //计算操作杆的相对位置 float length = target.localPosition.magnitude; //如果操纵杆超过了摇杆的范围，则将操纵杆设置为最大半径 if (length > radius) { target.localPosition = Vector3.ClampMagnitude (target.localPosition, radius); } //在Inspector显示操纵杆位置 position = target.localPosition; //将操纵杆相对位置映射到【-1，1】之间 position = position / radius * Mathf.InverseLerp (radius, 2, 1); } /// <summary> /// 当操纵杆结束拖动时触发 /// </summary> public void OnEndDrag(PointerEventData data) { //拖拽结束，将操纵杆恢复到默认位置 position = Vector2.zero; target.position = transform.position; }}

2.如图创建UGUI，所用资源可在网上自行下载。

效果图如下：

3.打包运行即可。这样一个简单的虚拟摇杆就实现了。

下面是对以上虚拟摇杆代码的扩展（ps：只是多了一些事件，便于其他脚本访问使用）废话不多说来代码了

using System;using UnityEngine;using UnityEngine.UI;using UnityEngine.EventSystems; // // Joystick component for controlling player movement and actions using Unity UI events.// There can be multiple joysticks on the screen at the same time, implementing different callbacks.// public class UIJoystick : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler{ /// /// Callback triggered when joystick starts moving by user input. /// public event Action onDragBegin; /// /// Callback triggered when joystick is moving or hold down. /// public event Action onDrag; /// /// Callback triggered when joystick input is being released. /// public event Action onDragEnd; /// /// The target object i.e. jostick thumb being dragged by the user. /// public Transform target; /// /// Maximum radius for the target object to be moved in distance from the center. /// public float radius = 50f; /// /// Current position of the target object on the x and y axis in 2D space. /// Values are calculated in the range of [-1, 1] translated to left/down right/up. /// public Vector2 position; //keeping track of current drag state private bool isDragging = false; //reference to thumb being dragged around private RectTransform thumb; //initialize variables void Start() { thumb = target.GetComponent(); //in the editor, disable input received by joystick graphics: //we want them to be visible but not receive or block any input #if UNITY_EDITOR Graphic[] graphics = GetComponentsInChildren(); // for(int i = 0; i < graphics.Length; i++) // graphics[i].raycastTarget = false; #endif } /// /// Event fired by UI Eventsystem on drag start. /// public void OnBeginDrag(PointerEventData data) { isDragging = true; if(onDragBegin != null) onDragBegin(); } /// /// Event fired by UI Eventsystem on drag. /// public void OnDrag(PointerEventData data) { //get RectTransforms of involved components RectTransform draggingPlane = transform as RectTransform; Vector3 mousePos; //check whether the dragged position is inside the dragging rect, //then set global mouse position and assign it to the joystick thumb if (RectTransformUtility.ScreenPointToWorldPointInRectangle(draggingPlane, data.position, data.pressEventCamera, out mousePos)) { thumb.position = mousePos; } //length of the touch vector (magnitude) //calculated from the relative position of the joystick thumb float length = target.localPosition.magnitude; //if the thumb leaves the joystick's boundaries, //clamp it to the max radius if (length > radius) { target.localPosition = Vector3.ClampMagnitude(target.localPosition, radius); } //set the Vector2 thumb position based on the actual sprite position position = target.localPosition; //smoothly lerps the Vector2 thumb position based on the old positions position = position / radius * Mathf.InverseLerp(radius, 2, 1); } //set joystick thumb position to drag position each frame void Update() { //in the editor the joystick position does not move, we have to simulate it //mirror player input to joystick position and calculate thumb position from that #if UNITY_EDITOR target.localPosition = position * radius; target.localPosition = Vector3.ClampMagnitude(target.localPosition, radius); #endif //check for actual drag state and fire callback. We are doing this in Update(), //not OnDrag, because OnDrag is only called when the joystick is moving. But we //actually want to keep moving the player even though the jostick is being hold down if(isDragging && onDrag != null) onDrag(position); } /// /// Event fired by UI Eventsystem on drag end. /// public void OnEndDrag(PointerEventData data) { //we aren't dragging anymore, reset to default position position = Vector2.zero; target.position = transform.position; //set dragging to false and fire callback isDragging = false; if (onDragEnd != null) onDragEnd(); }}

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