Unity3D基于UGUI实现虚拟摇杆

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;
 }
}

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();
  }
}