openGl glGetUniformLocation returns -1

openGl glGetUniformLocation returns -1

**它总是 returns -1 ,这里是代码

simple_fragment_shader

precision mediump float;
varying vec4 v_Color;
void main()
{
    gl_FragColor = v_Color;
}

simple_vertex_shader

attribute vec4 a_Position;
attribute vec4 a_Color;
varying vec4 v_Color;
void main()
{
    v_Color = a_Color;
    gl_Position = a_Position;
    gl_PointSize = 10.0;
}

为什么aColorLocation = glGetUniformLocation(program, A_COLOR)返回-1

其中 private val A_COLOR = "a_Color"

program = 3

a_Color 是一个属性。使它成为制服或使用 glGetAttribLocation.