虛擬搖桿在移動遊戲開發中，是很常見的需求，今天我們在Unity中，使用UGUI來實現一個簡單的虛擬搖桿功能。

1.開啟Unity，新建立一個UIJoystick.cs指令碼，程式碼如下：

using UnityEngine;
using UnityEngine.EventSystems;
 
public class UIJoystick : MonoBehaviour,IDragHandler,IEndDragHandler
{  
  /// <summary>
 /// 被使用者拖動的操縱桿
  /// </summary>
  public Transform target;
 
  /// <summary>
 /// 操縱桿可移動的最大半徑
  /// </summary>
  public float radius = 50f;
  
  /// <summary>
 /// 當前操縱桿在2D空間的x,y位置
  /// 搖桿按鈕的值【-1，1】之間
  /// </summary>
  public Vector2 position;
    
 //操縱桿的RectTransform元件
 private RectTransform thumb;
 
 void Start()
 {
 thumb = target.GetComponent<RectTransform>();
 }
 
  /// <summary>
 /// 當操縱桿被拖動時觸發
  /// </summary>
  public void OnDrag(PointerEventData data)
 {
 //獲取搖桿的RectTransform元件，以檢測操縱桿是否在搖桿內移動
 RectTransform draggingPlane = transform as RectTransform;
 Vector3 mousePos;
 
 //檢查拖動的位置是否在拖動rect內，
 //然後設定全域性滑鼠位置並將其分配給操縱桿
 if (RectTransformUtility.ScreenPointToWorldPointInRectangle (draggingPlane,data.position,data.pressEventCamera,out mousePos)) {
  thumb.position = mousePos;
 }
  
 //觸控向量的長度（大小）
 //計算操作杆的相對位置
 float length = target.localPosition.magnitude;
 
 //如果操縱桿超過了搖桿的範圍，則將操縱桿設定為最大半徑
 if (length > radius) {
  target.localPosition = Vector3.ClampMagnitude (target.localPosition,radius);
 }
  
 //在Inspector顯示操縱桿位置
 position = target.localPosition;
 //將操縱桿相對位置對映到【-1，1】之間
 position = position / radius * Mathf.InverseLerp (radius,2,1);
 }
  /// <summary>
 /// 當操縱桿結束拖動時觸發
  /// </summary>
  public void OnEndDrag(PointerEventData data)
 {
 //拖拽結束，將操縱桿恢復到預設位置
 position = Vector2.zero;
 target.position = transform.position;
 }
}

2.如圖建立UGUI，所用資源可在網上自行下載。

效果圖如下：

3.打包執行即可。這樣一個簡單的虛擬搖桿就實現了。

下面是對以上虛擬搖桿程式碼的擴充套件（ps：只是多了一些事件，便於其他指令碼訪問使用）廢話不多說來程式碼了

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,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,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,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();
  }
}

以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支援我們。