Doesn't show sprites in thread - libgdx

Question

I make simple game using libgdx. I want to display sprites in other thread (not in main thread). But If I run there are not sprites. In my logcat I see the instance of sprites but the graphic doesn,t display.
my code :
#Override
public void render() {
Gdx.gl.glClearColor(1, 1, 1, 1);
Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);
rbg.render();
camera.update();
Thread th = new Thread(new Runnable(){
#Override
public void run() {
Gdx.app.postRunnable(new Runnable(){
#Override
public void run() {
camera.update();
batch.getProjectionMatrix();
pokazPostac();
}
});
}
});
th.start();
}
public void pokazPostac(){
Random r = new Random();
batch.setProjectionMatrix(camera.combined);
spriteb.setSize(64, 100);
batch.begin();
switch (r.nextInt(6)){
case 0:
spriteb.setPosition(64, 128);
spriteb.draw(batch);
Gdx.app.log("", ""+spriteb.getX());
break;
case 1:
spriteb.draw(batch);
spriteb.setPosition(192, 256);
break;
case 2:
spriteb.draw(batch);
spriteb.setPosition(320, 128);
break;
case 3:
spriteb.draw(batch);
spriteb.setPosition(448, 256);
break;
case 4:
spriteb.draw(batch);
spriteb.setPosition(640, 128);
break;
case 5:
spriteb.draw(batch);
spriteb.setPosition(704, 256);
break;
}
batch.end();
}

Answer 1

Because you tagged this as OpenGL then you should keep in mind that OpenGL is single threaded and with the exception of probably some new features multi threaded rendering is considered an error.
So normally you create a window, assign OpenGL to that and just after that you can call OpenGL functions. So if any of these steps are done in different threads it will most likely fail. So basically when you create a context it can only be current in 1 thread, you can switch if you want but that may introduce a slowdown. So because your context is current in thread 1 and you attempt to call OpenGL functions from thread 2 those calls will fail because the current context is none for thread 2.
What you can do however is, you update where you want, like do "physics" in a separate thread and commit these changes into the rendering thread, but even in this case you must render from the same thread you created the window + initialized OpenGL from or just simply stick to a single threaded design.