Q:

LibGDX stage fading to black color

I have multiple screens with stages in my game and I have been implementing a simple fade transition between them. 
It works now, but I want that the screen fades out to black. The clear color of the game is white, though, so only the stage is obviously faded out, and the background keeps white. I have tried adding Actions.color(Color.BLACK, Interpolation.fade) to the stage but nothing really happens at all. 
How could I implement the fade transition correctly?

A:

Stage doesn't have drawable content only a group that contains all children.
So create full Screen black Image and add to stage as background. Then inside show() that make it white by action, as your required background. 
@Override
public void show() {

    final Image image=new Image(new TextureRegion(GdxTest.getTexture()));
    image.setSize(stage.getWidth(),stage.getHeight());
    image.setOrigin(stage.getWidth()/2,stage.getHeight()/2);
    image.setColor(Color.BLACK);

    stage.addActor(image);
    stage.addListener(new ClickListener(){

        @Override
        public void clicked(InputEvent event, float x, float y) {

            image.addAction(Actions.sequence(Actions.color(Color.BLACK,2),Actions.run(new Runnable() {
                @Override
                public void run() {
                    ((GdxTest)Gdx.app.getApplicationListener()).setScreen(new SecondScreen());
                }
            })));

            super.clicked(event, x, y);
        }
    });

    image.addAction(Actions.color(Color.WHITE,2)); 
}

getTexture() method
public static Texture getTexture(){

    Pixmap pixmap;
    try {
        pixmap = new Pixmap(1, 1, Pixmap.Format.RGBA8888);
    }catch (GdxRuntimeException e)
    {
        pixmap=new Pixmap(1,1, Pixmap.Format.RGB565);
    }
    pixmap.setColor(Color.WHITE);
    pixmap.drawRectangle(0,0,1,1);

    return new Texture(pixmap);
}

