Java SE (Java Platform, Standard Edition)

I have a JPanel "mainPanel" that I want to add and remove other JPanels to, when a user changes from screen to screen. Right now I have it set up so that mainPanel has a 1x1 GridLayout,

JPanel mainPanel = new JPanel();
GridLayout gridLayout = new GridLayout();
gridLayout.setRows(1);
gridLayout.setColumns(1);
mainPanel.setLayout(gridLayout);


JPanel currentScreen = new JPanel();
mainPanel.add(currentScreen,null);
mainPanel.setVisible(true);

JPanel newScreen = new JPanel();
mainPanel.setVisible(false);

public void getScreen(JPanel new_Screen) {
   currentScreen.setVisible(false);
   mainPanel.add(new_Screen, null);
}

This successfully hides the currentScreen, but adds a new GirdLayout cell, making each JPanel take up 50% of the mainPanel (whereas I want newScreen to take up the entire mainPanel).

So I tried the following,

public void getScreen(JPanel new_Screen) {
   mainPanel.remove(currentScreen);
   mainPanel.add(new_Screen, null);
}

Which doesn't do anything, currentScreen is the only thing left showing.
So I changed it to this,

public void getScreen(JPanel new_Screen) {
   mainPanel.remove(currentScreen);
   mainPanel.repaint();
   mainPanel.add(new_Screen, null);
}

and now the mainPanel is completely blanked out. This is all counterintuitive to me, and seems like it should be an easy problem to overcome.

Is there a better way of doing this?

I briefly tried making mainPanel a JLayeredPane instead of JPanel but it wasn't working for me...

I want the added JPanels to take up 100% of mainPanel, and simply make the one I want to see visible. Is there a layout I'm missing that will allow this?