如何在面板上垂直堆疊文本字段？

Question

我正在研究GUI GUI GPA計算程序。我設置了我的按鈕，這樣一旦它被點擊，一些文本字段和組合框將被添加到面板中，但每次點擊時，所有附加組件都以單行水平排列。有沒有一種方法來操縱佈局，以便新的附加組件可以在現有組件下面新建一行？謝謝！

這裏是我的代碼：

public class gpaCalculator extends JFrame { 
    ArrayList<Class> allClasses = new ArrayList<Class>(); 
    ArrayList<Class> classesTaken = new ArrayList<Class>(); 
    ArrayList<Class> classesTaking = new ArrayList<Class>(); 
    ArrayList<Class> classesWillTake = new ArrayList<Class>(); 

    private JFrame frame; 
    private JPanel panel1; 
    private JPanel panel2; 
    private JPanel panel3; 

    private JButton addNewCourse; 
    private JButton finishedCalculate; 
    private JButton showClassesEntered; 
    private JButton removeAllClass; 

    /** 
    * Courses 
    **/ 
    public gpaCalculator() { 
     frame = new JFrame("GPA Calculator"); 
     this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
     int height = (int) Toolkit.getDefaultToolkit().getScreenSize().getHeight(); 
     int width = (int) Toolkit.getDefaultToolkit().getScreenSize().getWidth(); 
     this.setSize(width, height); 
     this.setLayout(new FlowLayout(8)); 
     panel1 = new JPanel(new FlowLayout(FlowLayout.LEFT)); 
     panel2 = new JPanel(new FlowLayout(FlowLayout.CENTER)); 
     panel3 = new JPanel(new FlowLayout(FlowLayout.RIGHT)); 

     addNewCourse = new JButton("Add a new course!"); 
     addNewCourse.addActionListener(new ButtonListener()); 

     finishedCalculate = new JButton("Calculate my GPA & Enter target GPA"); 
     finishedCalculate.addActionListener(new ButtonListener2()); 

     showClassesEntered = new JButton("Display classes entered"); 
     showClassesEntered.addActionListener(new ButtonListener3()); 

     removeAllClass = new JButton("Remove all entered classes"); 
     removeAllClass.addActionListener(new ButtonListener4()); 

     this.add(addNewCourse); 
     this.add(finishedCalculate); 
     this.add(showClassesEntered); 
     this.add(removeAllClass); 

     this.add(panel1); 
     this.add(panel2); 
     this.add(panel3); 

     this.setLocationRelativeTo(null); 
     this.setVisible(true); 
    } 

    private class ButtonListener implements ActionListener { 

     @Override 
     public void actionPerformed(ActionEvent args) { 

      String[] courseCreditHourCombo = {"1", "2", "3", "4"}; 
      String[] courseGradeCombo = {"A+", "A", "A-", "B+", "B", "B-", "C+", "C", "C-", "D", "E", "F", "U"}; 
      String[] courseTypeCombo = {"Have taken", "Currently taking", "Will be taking"}; 
      JLabel creditHourLabel = new JLabel("Course credit houe"); 
      JLabel nameLabel = new JLabel("Course name: "); 
      JLabel calculatedGPALabel = new JLabel("Calculated GPA"); 
      JLabel courseTypeLabel = new JLabel("Course status"); 
      JLabel gradeLabel = new JLabel("Course grade "); 
      JComboBox courseCreditHour = new JComboBox(courseCreditHourCombo); 
      JTextField courseName = new JTextField(10); 
      courseName.setEditable(true); 
      JComboBox courseGrade = new JComboBox(courseGradeCombo); 
      JComboBox courseType = new JComboBox(courseTypeCombo); 
      JTextField calculatedGPA = new JTextField(10); 

      panel1.add(nameLabel); 
      panel1.add(courseName); 
      panel1.add(creditHourLabel); 
      panel1.add(courseCreditHour); 
      panel1.add(courseTypeLabel); 
      panel1.add(courseType); 
      panel1.add(gradeLabel); 
      panel1.add(courseGrade); 

      int classCredit = (Integer) courseCreditHour.getEditor().getItem(); 
      String className = courseName.getText(); 
      String classGrade = (String) courseGrade.getEditor().getItem(); 
      String classType = (String) courseType.getEditor().getItem(); 

      Class theClass = new Class(className, classGrade, classType, classCredit); 
      allClasses.add(theClass); 

      if (classType.equals("Have taken")) { 
       Class newClass = new Class(className, classGrade, classType, classCredit); 
       classesTaken.add(newClass); 
      } else if (classType.equals("Currently taking")) { 
       Class newClass = new Class(className, classType, classCredit); 
       classesTaking.add(newClass); 
      } else { 
       Class newClass = new Class(className, classType, classCredit); 
       classesWillTake.add(newClass); 
      } 
     } 
    } 

    private class ButtonListener2 implements ActionListener { 

     @Override 
     public void actionPerformed(ActionEvent arg0) { 
      // TODO Auto-generated method stub 
      panel2.removeAll(); 
      JLabel currentGPALabel = new JLabel("Current GPA: "); 
      JLabel currentGPA = new JLabel(); 
      JLabel targetGPALabel = new JLabel("Target GPA: "); 
      JTextField targetGPA = new JTextField(10); 
      targetGPA.setEditable(true); 

      panel2.setSize(200, 200); 
      panel2.add(currentGPALabel); 
      panel2.add(currentGPA); 
      panel2.add(targetGPALabel); 
      panel2.add(targetGPA); 

      double counter = 0; 
      for (Class c : classesTaken) { 
       counter = counter + c.getWeightedClassGPA(); 
      } 
      double currentGPADouble = counter/(classesTaken.size() + 1); 
      currentGPA.setText(String.valueOf(currentGPADouble)); 
      //System.out.println(currentGPADouble); 
     } 
    } 

    private class ButtonListener3 implements ActionListener { 
     @Override 
     public void actionPerformed(ActionEvent arg0) { 
      // TODO Auto-generated method stub 
      panel3.removeAll(); 
      JLabel classesEntered = new JLabel("Courses entered: "); 

      panel3.setSize(200, 200); 
      panel3.add(classesEntered); 

      classesEntered.setText("Classes entered: " + allClasses); 
     } 
    } 

    private class ButtonListener4 implements ActionListener { 
     @Override 
     public void actionPerformed(ActionEvent e) { 
      // TODO Auto-generated method stub 
      allClasses.clear(); 
     } 
    } 
} 

Answer 1

將它們裝入的GridBagLayout。

http://docs.oracle.com/javase/6/docs/api/java/awt/GridBagLayout.html