为什么Swing在这里推迟'全面绘制'JFrame？

Question

我在这里遇到了我的代码问题，我无法解释。我有两个Jframes，第一个有一个按钮，点击它时会导致第二帧。这工作正常。但是有一个问题在这里：第一帧出现为skeleton，没有添加JComponents。它正在等待，直到所有的语句都被执行，即paints的JComponents的JFrame显示为skeleton。

这是为什么？我怎样才能在执行下一行代码之前“完全显示/绘制”所有组件？

下面是我的代码

import java.awt.Dimension; 
import java.awt.FlowLayout; 
import java.awt.event.ActionEvent; 
import java.util.logging.Level; 
import java.util.logging.Logger; 
import javax.swing.JButton; 
import javax.swing.JFrame; 
import javax.swing.JLabel; 

/** 
* 
* @author JWizard 
*/ 
public class Test { 

    private JFrame frame; 
    private JButton button; 

    public Test() { 
     initGUI(); 
     button.addActionListener((ActionEvent e) -> { 
      JFrame frame1 = new JFrame("Second Jframe"); 
      frame1.setPreferredSize(new Dimension(300, 300)); 
      frame1.getContentPane().add(new JLabel("Swing Component")); 
      frame1.pack(); 
      frame1.setVisible(true); 
      frame1.setLocationRelativeTo(null); 
      /** 
      * After executing the above line, 
      * 'frame1.setLocationRelativeTo(null);', I am expecting the program 
      * to have fully "painted" my fame1 GUI, showing the label. 
      */ 
      try { 
       Thread.sleep(7000); 
       System.out.println("statement 1"); 
       Thread.sleep(7000); 
       System.out.println("statement 2");//after executing this statment thats when 
       //the program paints the components of frame1 
      } catch (InterruptedException ex) { 
       Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); 
      } 
     }); 

    } 

    private void initGUI() { 
     frame = new JFrame("Frame 1"); 
     button = new JButton("Go to Frame 2"); 
     frame.setLayout(new FlowLayout(FlowLayout.LEADING)); 
     frame.setPreferredSize(new Dimension(300, 300)); 
     frame.getContentPane().add(button); 
     frame.pack(); 
     frame.setVisible(true); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     frame.setLocationRelativeTo(null); 

    } 

    public static void main(String[] args) { 
     Test text = new Test(); 
    } 

} 

Answer 1

试试这个：

public Test() { 
     initGUI(); 
     button.addActionListener((ActionEvent e) -> { 
      JFrame frame1 = new JFrame("Second Jframe"); 
      frame1.setPreferredSize(new Dimension(300, 300)); 
      frame1.getContentPane().add(new JLabel("Swing Component")); 
      frame1.pack(); 
      frame1.setVisible(true); 
      frame1.setLocationRelativeTo(null); 

      new SwingWorker<Void, Void>() { 
       @Override 
       protected Void doInBackground() throws Exception { 
        try { 
         Thread.sleep(7000); 
         System.out.println("statement 1"); 
         Thread.sleep(7000); 
         System.out.println("statement 2"); 
        } catch (InterruptedException ex) { 
         Logger.getLogger(Test.class.getName()).log(Level.SEVERE, null, ex); 
        } 
        return null; 
       } 
      }.execute(); 
     }); 

}