nulllayoutframe.java

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package layout;

import java.awt.*;
import javax.swing.*;

public class NullLayoutFrame extends JFrame {
  JPanel contentPane;
  //创建3个按钮
  JButton jButton1 = new JButton();
  JButton jButton2 = new JButton();
  JButton jButton3 = new JButton();

  public NullLayoutFrame() {
    try {
      setDefaultCloseOperation(EXIT_ON_CLOSE);
      jbInit();
    }
    catch(Exception e) {
      e.printStackTrace();
    }
  }
  
  public static void main(String[] args) {
    NullLayoutFrame frame = new NullLayoutFrame();
    Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
    Dimension frameSize = frame.getSize();
    frame.setLocation((screenSize.width - frameSize.width) / 2,
        (screenSize.height - frameSize.height) / 2);
    frame.setVisible(true);
  }

  private void jbInit() throws Exception  {
    contentPane = (JPanel) this.getContentPane();
    //将布局设为null
    contentPane.setLayout(null);
    this.setSize(new Dimension(400, 300));
    this.setTitle("NullLayout示例");
    jButton1.setText("jButton1");
    jButton2.setText("jButton2");
    jButton3.setText("jButton3");
    //设置按钮的位置和大小
    jButton1.setBounds(new Rectangle(26, 25, 98, 157));
    jButton2.setBounds(new Rectangle(130, 25, 251, 52));
    jButton3.setBounds(new Rectangle(129, 85, 252, 97));
    //为窗口面板加入按钮
    contentPane.add(jButton1, null);
    contentPane.add(jButton2, null);
    contentPane.add(jButton3, null);
  }
}