Unity3D 自定义UI组件画圆、圆弧、扇形

来源：https://forum.unity3d.com/threads/draw-circles-or-primitives-on-the-new-ui-canvas.272488/

效果：





代码：

using UnityEngine;
using UnityEngine.UI;

public class DrawSquald : MaskableGraphic
{
[SerializeField]
Texture m_Texture;

[Range(0, 1)]
[SerializeField]
private float fillAmount;

public float FillAmount
{
get { return fillAmount; }
set
{
fillAmount = value;

// This detects a change and sets the vertices dirty so it gets updated
//这会检测到一个更改，并将顶点设置为脏，以便它被更新
SetVerticesDirty();
}
}

//是否填充
public bool fill = true;
//圆弧厚度
public int thickness = 5;

//分段
[Range(0, 360)]
public int segments = 360;

public override Texture mainTexture
{
get
{
return m_Texture == null ? s_WhiteTexture : m_Texture;
}
}

/// <summary>
/// Texture to be used.
/// </summary>
public Texture texture
{
get { return m_Texture; }

set
{
if (m_Texture == value)
return;
m_Texture = value;
SetVerticesDirty();
SetMaterialDirty();
}
}

// Using arrays is a bit more efficient 使用数组更有效率
UIVertex[] uiVertices = new UIVertex[4];
Vector2[] uvs = new Vector2[4];
Vector2[] pos = new Vector2[4];

protected override void Start()
{
uvs[0] = new Vector2(0, 1);
uvs[1] = new Vector2(1, 1);
uvs[2] = new Vector2(1, 0);
uvs[3] = new Vector2(0, 0);
}

protected override void OnPopulateMesh(VertexHelper vh)
{
float outer = -rectTransform.pivot.x * rectTransform.rect.width;
float inner = -rectTransform.pivot.x * rectTransform.rect.width + thickness;

float degrees = 360f / segments;
int fa = (int)((segments + 1) * this.fillAmount);

// Updated to new vertexhelper
vh.Clear();

// Changed initial values so the first polygon is correct when circle isn't filled
float x = outer * Mathf.Cos(0);
float y = outer * Mathf.Sin(0);
Vector2 prevX = new Vector2(x, y);

// Changed initial values so the first polygon is correct when circle isn't filled
x = inner * Mathf.Cos(0);
y = inner * Mathf.Sin(0);
Vector2 prevY = new Vector2(x, y);

for (int i = 0; i < fa - 1; i++)
{
// Changed so there isn't a stray polygon at the beginning of the arc
//改变了，所以在圆弧的开头没有一个杂散多边形
float rad = Mathf.Deg2Rad * ((i + 1) * degrees);
float c = Mathf.Cos(rad);
float s = Mathf.Sin(rad);

pos[0] = prevX;
pos[1] = new Vector2(outer * c, outer * s);

if (fill)
{
pos[2] = Vector2.zero;
pos[3] = Vector2.zero;
}
else
{
pos[2] = new Vector2(inner * c, inner * s);
pos[3] = prevY;
}

// Set values for uiVertices
for (int j = 0; j < 4; j++)
{
uiVertices[j].color = color;
uiVertices[j].position = pos[j];
uiVertices[j].uv0 = uvs[j];
}

// Get the current vertex count
int vCount = vh.currentVertCount;

// If filled, we only need to create one triangle
vh.AddVert(uiVertices[0]);
vh.AddVert(uiVertices[1]);
vh.AddVert(uiVertices[2]);

// Create triangle from added vertices
vh.AddTriangle(vCount, vCount + 2, vCount + 1);

// If not filled we need to add the 4th vertex and another triangle
if (!fill)
{
vh.AddVert(uiVertices[3]);
vh.AddTriangle(vCount, vCount + 3, vCount + 2);
}

prevX = pos[1];
prevY = pos[2];
}
}
}
使用：

使用就很简单了，附加到一个空的GameObject上面，由于是UI组件，因此需要放在Canvas下面。具体参数的功能可以参照效果图。

版本要求5.2及以上....最低版本具体是5.2还是5.3给忘了...