Libgdx - FrameBuffer rendering and FitViewport - libgdx

Question

I use ortho camera and FitViewport at my project.
In my render() method i create a fremeBuffer to store actual state of my game, then create a pixmap of that buffer and finally i set a new shader and do my postprocess stuff with that frame:
//--- render frame to buffer
screenBuffer.begin();
camera.update();
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.draw(img, 0, 0);
batch.end();
stage.draw();
//--- create pixmap from that buffer
pixmap = ScreenUtils.getFrameBufferPixmap(0, 0,screenBuffer.getWidth(), screenBuffer.getHeight());
batch.flush();
screenBuffer.end();
//--- create texture from pixmap
renderedScreenTexture = new Texture(pixmap);
//--- finally render frame with postprocess shader
camera.update();
Gdx.gl.glClearColor(1, 0, 0, 1);
Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
batch.setShader(monoShader);
batch.setProjectionMatrix(camera.combined);
batch.begin();
batch.draw(renderedScreenTexture, 0,0);
batch.draw(renderedScreenTexture, 0, 0, 640, 320, 0, 0, 640, 320, false, true);
batch.end();
At my resize method I have:
viewport.update(width, height);
camera.position.set(camera.viewportWidth / 2,camera.viewportHeight / 2, 0);
The problem is that after resizing a window FitViewport doesen't work.
When i remove a creating frameBuffer from render method FitViewport works fine.
Can anybody tell me what is wrong with my code or whole concept?

Answer 1

Try this:
// the viewPort you are using
FitViewport v = viewport;
// end your buffer with your viewPort's position and size
screenBuffer.end(v.getScreenX(),v.getScreenY(),
v.getScreenWidth(),v.getScreenHeight());

Answer 2

You may have to call fitViewport.apply() before drawing your frameBuffer.