Can't work FlowLayout with a JPanel, but can with contentPane...

Question

Hi,
I usually use setBounds to layout my components but I am trying FlowLayout and GridLayout this time. I tried FlowLayout and got it to work when not using a JPanel. But when I try adding the JTextField to a JPanel like in the code below, the JTextField doesn't appear and only the yellow background appears. I don't know why. Thanks for your help.
       Container contentPane = getContentPane();
       contentPane.setBackground( Color.YELLOW );
       registerJPanel = new JPanel();
       registerJPanel.setLayout(new FlowLayout());
       usernameloginJTextField = new JTextField("hi");
       registerJPanel.add(usernameloginJTextField);
       setTitle( "Application");
       setSize( 400,400);
       setVisible( true );

Answer 1

know how i can put each new component on a new line?
registerJPanel.setLayout(new GridLayout(0,1));