我要评论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();
}
}
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持移动技术网。
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