Java GridBagLayout组件未全屏显示

问题描述：

我是Java新手，尝试使用GridBagLayout生成我的第一个GUI。使用下面的代码，我得到我的全屏，但不显示组件“label_url_eingabe”和“url_eingabe”（空窗口）。当我最小化窗口时，它们被显示！当我将窗口大小设置为特定值时，我会得到相同的行为。所以这些组件在我的程序的最初开始时并未显示。Java GridBagLayout组件未全屏显示

package ofb_reader_package; 

import javax.swing.JFrame; 
import javax.swing.JLabel; 
import javax.swing.JTextField; 
import java.awt.GridBagConstraints; 
import java.awt.GridBagLayout; 

public class OFB_Reader_GUI extends JFrame { 

// Definition der GUI Komponenten 

    // Eingabefeld URL 

    JLabel label_url_eingabe; 
    JTextField url_eingabe; 

    //this.OFB_Reader_GUI(); 

// Eigenschaften Hauptfenster "OFB_Reader_GUI" 
    public OFB_Reader_GUI() { 

     // Eigenschaften Hauptfenster 
     setVisible(true); 
     setSize(500, 300); 
     setDefaultCloseOperation(EXIT_ON_CLOSE); 
     setLocationRelativeTo(null); 
     setTitle("Mark's OFB Reader"); 
     setResizable(true); 
     setExtendedState(JFrame.MAXIMIZED_BOTH); 
     setLayout(null); 




     this.label_url_eingabe = new JLabel("URL:"); 
     this.url_eingabe = new JTextField(10); 

     this.getContentPane().setLayout(new GridBagLayout()); 
     GridBagConstraints c = new GridBagConstraints(); 


     // POSITIONIERUNGEN MIT GRIDBAGLAYOUT 

     // URL Eingabe Label und Einghabefeld 
     c.fill = GridBagConstraints.HORIZONTAL; 
     c.gridx = 0; 
     c.gridy = 0; 
     c.ipadx = 35; 
     c.weightx = 1.0; 
     c.weighty = 1.0; 
     c.anchor = GridBagConstraints.NORTHWEST; 
     this.getContentPane().add(this.label_url_eingabe, c); 


     c.fill = GridBagConstraints.HORIZONTAL; 
     c.gridx = 1; 
     c.gridy = 0; 
     c.ipadx = 35; 
     c.weightx = 1.0; 
     c.weighty = 1.0; 
     c.anchor = GridBagConstraints.NORTHWEST; 
     add(this.url_eingabe, c); 

    } 
}

这是主要的：

package ofb_reader_package; 

import javax.swing.*; 



public class OFB_Reader_main_class { 

    public static void main(String[] args){ 

     new OFB_Reader_GUI(); 
     new OFB_Reader_main_class(); 

    } 
}

JFrame setVisible是** last **方法调用，而不是第一个。调用JFrame方法的顺序是最重要的**。在打包JFrame并使其可见之前，您必须创建Swing组件并将它们添加到JPanel或JFrame。最后，不要使用空布局。使用[Swing布局]（https://docs.oracle.com/javase/tutorial/uiswing/layout/visual.html）创建您的GUI。 –

答

非常感谢您的帮助！我现在明白了：

package ofb_reader_package; 

import javax.swing.*; 

import java.awt.*; 



public class OFB_Reader_GUI_and_Main { 





    public static void addComponentsToPane(Container pane) { 

     JLabel label_url_eingabe; 
     JTextField url_eingabe; 

     pane.setLayout(new GridBagLayout()); 
     GridBagConstraints c = new GridBagConstraints();   

     label_url_eingabe = new JLabel("URL:"); 
     c.fill = GridBagConstraints.HORIZONTAL; 
     c.gridx = 0; 
     c.gridy = 0; 
     pane.add(label_url_eingabe, c); 

     url_eingabe = url_eingabe = new JTextField(10); 
     c.fill = GridBagConstraints.HORIZONTAL; 
     c.gridx = 1; 
     c.gridy = 0; 
     pane.add(url_eingabe, c); 

    } 

    private static void createAndShowGUI() { 
     //Create and set up the window. 
     JFrame frame = new JFrame("GridBagLayoutDemo"); 
     frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 

     //Set up the content pane. 
     addComponentsToPane(frame.getContentPane()); 

     //Display the window. 
     frame.pack(); 
     frame.setVisible(true); 
     } 






public static void main(String[] args){ 

    //Schedule a job for the event-dispatching thread: 
    //creating and showing this application's GUI. 
    javax.swing.SwingUtilities.invokeLater(new Runnable() { 
     public void run() { 
      createAndShowGUI(); 
     } 
    }); 
} 
}

Java GridBagLayout组件未全屏显示

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