Set component at center of the page

问题

How can I set a component (say button) at center of the panel?

I used Flowlayout with layout constraint as center, but I am getting button at top-center position of the panel.

回答1:

This can be achieved using either GridBagLayout as mentioned by AVD¹ or BoxLayout. See this answer for sample code.

Personally I'd use GBL for this because fewer lines of code are required to get the component laid out & on-screen (centered in the parent container).

1. I do not understand why that answer is not getting more up-votes, but that aside..

回答2:

Use GridBagLayout instead of FlowLayout.

JPanel panel=new JPanel();
panel.setLayout(new GridBagLayout());
panel.add(new JButton("Sample")); // will use default value of GridBagConstraints

回答3:

Use a null layout and set the button's bounds, like this:

// assuming you're extending JPanel
private JButton button; // data field

...

this.setLayout(null);
this.addComponentListener(new ComponentAdapter(){
   public void componentResized(ComponentEvent e){
       setButtonBounds();
   }
});

private void setButtonBounds(){
   int bw = 90; // button width
   int bh = 30; // button height
   int w = getWidth();
   int h = getHeight();
   button.setBounds((w - bw) / 2, (h - bh) / 2, bw, bh);
}

If you start getting many buttons or a complex layout, consider using MigLayout.

来源：https://stackoverflow.com/questions/9090609/set-component-at-center-of-the-page