java中frame布局,Java Swing JFrame布局

I just wrote a simple code where I want a textfield and a button to appear on the main frame, but after running all I see is the textfield.

If I write the code of the button after the textfield then only the button is displayed.

Any idea why?

JFrame mainframe=new JFrame();

mainframe.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

mainframe.setBounds(0,0,200,200);

JButton jb=new JButton();

jb.setText("Leech");

mainframe.add(jb);

JTextField link=new JTextField(50);

mainframe.add(link);

mainframe.pack();

mainframe.setVisible(true);

解决方案

Add your components to a JPanel and then add that panel to the ContentPane of JFrame.

JFrame window = new JFrame();

JPanel mainframe = new JPanel();

window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

window.setBounds(0,0,200,200);

JButton jb = new JButton();

jb.setText("Leech");

mainframe.add(jb);

JTextField link = new JTextField(50);

mainframe.add(link);

window.getContentPane().add(mainframe);

window.pack();

window.setVisible(true);