render to FrameBuffer not working in combination with ShapeRenderer in a custom Actor (libgdx) - libgdx

Question

I try to implement a custom Actor which displays contents of a FrameBuffer by extending Image. Inside I'd like to draw using a ShapeRenderer.
public class CustomActor extends Image {
private FrameBuffer frameBuffer = null;
private ShapeRenderer shapeRenderer = new ShapeRenderer();
private int width;
private int height;
public CustomActor() {
width = Gdx.graphics.getWidth();
height = Gdx.graphics.getHeight();
shapeRenderer.setAutoShapeType(true);
}
#Override
public void draw(Batch batch, float parentAlpha) {
if (frameBuffer == null) {
frameBuffer = new FrameBuffer(Pixmap.Format.RGB565, width / 2, height / 2, false);
TextureRegion textureRegion = new TextureRegion(frameBuffer.getColorBufferTexture());
textureRegion.flip(false, true);
setDrawable(new TextureRegionDrawable(textureRegion));
}
frameBuffer.begin();
// render content
Gdx.gl.glClearColor(0, 1, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
shapeRenderer.begin(ShapeRenderer.ShapeType.Filled);
shapeRenderer.setColor(Color.WHITE);
shapeRenderer.rect(0, 0, frameBuffer.getWidth() / 2, frameBuffer.getHeight() / 2);
shapeRenderer.end();
if (frameBuffer != null) {
frameBuffer.end();
}
super.draw(batch, parentAlpha);
}
}
When deleting the ShapeRenderer part I can see the green background in the scene. But as soon as I use the ShapeRenderer the content is black. There is no white rectangle visible.
Any ideas what I am doing wrong?

Answer 1

Just found out that using my own SpriteBatch (with begin() and end()) after the FrameBuffer end() it works. So the problem seems to have to do with the calling order of the FrameBuffers methods and the SpriteBatches methods. Ending the given actor batch before beginning the FrameBuffer and "re"-beginning it to draw the actor is also working (see comment above).