An example of drawing a triangle in Android using Scala. Converted from an example in Pro Android 3 http://www.apress.com/9781430232223

MyActivity.scala

package com.example.AndroidPlaytime

import javax.microedition.khronos.opengles.GL10
import javax.microedition.khronos.egl.EGLConfig
import android.opengl.{GLSurfaceView, GLU}
import android.content.Context
import java.nio.{ByteOrder, ByteBuffer}
import android.app.Activity
import android.os.Bundle
import android.view.Window

class MyActivity extends Activity {
  var view: GLSurfaceView = null

  override def onPause() = {
    super.onPause()
    view.onPause()
  }

  override def onResume() = {
    super.onResume()
    view.onResume()
  }

  override def onCreate(savedInstanceState: Bundle) = {
    super.onCreate(savedInstanceState)
    requestWindowFeature(Window.FEATURE_NO_TITLE)

    view = new GLSurfaceView(this)
    view.setEGLConfigChooser(8 , 8, 8, 8, 16, 0)
    view.setRenderer(new SimpleTriangleRender(this))
    // view.setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY)
    view.setRenderMode(GLSurfaceView.RENDERMODE_CONTINUOUSLY)

    this.setContentView(view)
  }
}

abstract class AbstractRenderer extends android.opengl.GLSurfaceView.Renderer {
  def draw(gl:GL10)

  def onDrawFrame(gl: GL10) = {
    gl.glDisable(GL10.GL_DITHER)
    gl.glClear(GL10.GL_COLOR_BUFFER_BIT | GL10.GL_DEPTH_BUFFER_BIT)
    gl.glMatrixMode(GL10.GL_MODELVIEW)
    gl.glLoadIdentity()
    GLU.gluLookAt(gl, 0f, 0f, -5f, 0f, 0f, 0f, 0f, 1.0f, 0f)
    gl.glEnableClientState(GL10.GL_VERTEX_ARRAY)
    draw(gl)
  }

  def onSurfaceChanged(gl: GL10, width: Int, height: Int) = {
    gl.glViewport(0,0,width,height)
    val ratio:Float = width/height
    gl.glMatrixMode(GL10.GL_PROJECTION)
    gl.glLoadIdentity()
    gl.glFrustumf(-ratio, ratio, -1, 1,3,7)
  }

  def onSurfaceCreated(gl: GL10, config: EGLConfig) = {
    gl.glDisable(GL10.GL_DITHER)
    gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_FASTEST)
    gl.glClearColor(0.5f, 0.5f, 0.5f, 1)
    gl.glShadeModel(GL10.GL_SMOOTH)
    gl.glEnable(GL10.GL_DEPTH_TEST)
  }
}

class SimpleTriangleRender(context:Context) extends AbstractRenderer
{
  private[this] val verts = 3

  private[this] val vbb = ByteBuffer.allocateDirect(verts * 3 * 4)
  vbb.order(ByteOrder.nativeOrder())

  private[this] val ibb = ByteBuffer.allocateDirect(verts * 2)
  ibb.order(ByteOrder.nativeOrder())

  private[this] val vertBuffer = vbb.asFloatBuffer()

  private[this] val indexBuffer = ibb.asShortBuffer()

  private[this] val coords: Array[Float] = List(
    -0.5f, -0.5f, 0.0f,
     0.5f, -0.5f, 0.0f,
     0.0f,  0.5f, 0.0f
  ).toArray

  (0 until verts).foreach(i =>
    (0 until 3).foreach(j => {
       vertBuffer.put(coords(i*3+j))
    })
  )

  private[this] val indexes = Array[Short](0, 1, 2)
  (0 until 3).foreach(j => {
     indexBuffer.put(indexes(j))
  })

  vertBuffer.position(0)
  indexBuffer.position(0)

  def draw(gl: GL10): Unit = {
    gl.glColor4f(1.0f, 0f, 0f, 0.5f)
    gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertBuffer)
    gl.glDrawElements(GL10.GL_TRIANGLES, verts, GL10.GL_UNSIGNED_SHORT, indexBuffer)
  }
}