如何使用動作偵聽器中設置的變量

Question

我在理解如何使用動作偵聽器來更改變量的值時遇到問題。

在我的程序中，我需要通過選擇一些單選按鈕來存儲用戶的選擇。

我有一個卡片佈局的主類，然後幾個類，每個是不同的面板。在其中一個面板中，我有一些單選按鈕，並將actionlistener作爲內部類。

當我嘗試在主類中打印變量值時，它會在用戶做出選擇之前立即打印，因爲我實例化面板類並從中獲取變量。由用戶改變。

我知道我不應該用線性方式來思考Java，但是我怎樣才能確保在用戶更改之後而不是之前獲取變量？我將無法做到這一點嗎？我知道我的思想存在一些缺陷，但我已經好幾年沒有適當地睡過，我無法理解這一點。

public class Screen3 extends JPanel{ 

JRadioButton addition = new JRadioButton("Addition"); 
JRadioButton subtraction = new JRadioButton("Subtraction"); 
JRadioButton multiplication = new JRadioButton("Multiplication"); 
JRadioButton division = new JRadioButton("Division"); 
JRadioButton all = new JRadioButton("All"); 

JRadioButton single = new JRadioButton("Single"); 
JRadioButton two = new JRadioButton("Double"); 
JRadioButton triple = new JRadioButton("Triple"); 
JRadioButton mix = new JRadioButton("Mix"); 

JRadioButton five = new JRadioButton("5"); 
JRadioButton ten = new JRadioButton("10"); 

private int type, digit, rounds; 

public Screen3() { 

JPanel firstButtonPanel = new JPanel(); 
    JPanel secondButtonPanel = new JPanel(); 
    ButtonGroup myFirstGroup = new ButtonGroup(); 
    ButtonGroup mySecondGroup = new ButtonGroup(); 

    myFirstGroup.add(addition); 
    myFirstGroup.add(subtraction); 
    myFirstGroup.add(multiplication); 
    myFirstGroup.add(division); 
    //myFirstGroup.add(all); 

    mySecondGroup.add(single); 
    mySecondGroup.add(two); 
    mySecondGroup.add(triple); 
    //mySecondGroup.add(mix); 

    firstButtonPanel.setLayout(new FlowLayout()); 
    firstButtonPanel.add(addition); 
    firstButtonPanel.add(subtraction); 
    firstButtonPanel.add(multiplication); 
    firstButtonPanel.add(division); 
    //firstButtonPanel.add(all); 

    secondButtonPanel.setLayout(new FlowLayout()); 
    secondButtonPanel.add(single); 
    secondButtonPanel.add(two); 
    secondButtonPanel.add(triple); 
    //secondButtonPanel.add(mix); 

    JPanel buttons = new JPanel(); 
    buttons.setLayout(new BorderLayout()); 
    buttons.add(selectionLabel, BorderLayout.NORTH); 
    buttons.add(firstButtonPanel, BorderLayout.CENTER); 
    buttons.add(secondButtonPanel, BorderLayout.SOUTH); 

ButtonGroup myThirdGroup = new ButtonGroup(); 
    JPanel endButtons = new JPanel(); 

    myThirdGroup.add(five); 
    myThirdGroup.add(ten); 

    endButtons.add(five); 
    endButtons.add(ten); 

    endPanel.setLayout(new BorderLayout()); 
    endPanel.add(rounds, BorderLayout.NORTH); 
    endPanel.add(endButtons, BorderLayout.CENTER); 

    setLayout(new BorderLayout()); 
    add(buttons, BorderLayout.NORTH); 

Selection sn = new Selection(); 

    addition.addActionListener(sn); 
    subtraction.addActionListener(sn); 
    multiplication.addActionListener(sn); 
    division.addActionListener(sn); 

    single.addActionListener(sn); 
    two.addActionListener(sn); 
    triple.addActionListener(sn); 

    five.addActionListener(sn); 
    ten.addActionListener(sn); 
} 

public int getType() { 
    return type; 
} 

public int getDigit() { 
    return digit; 
} 

public int getRounds() { 
    return rounds; 
} 

public class Selection implements ActionListener { 
    public void actionPerformed(ActionEvent e) { 
     if(addition.isSelected()) { 
      type = 1; 
     } 
     else if(subtraction.isSelected()) { 
      type = 2; 
     } 
     else if(multiplication.isSelected()) 
      type = 3; 
     else if(division.isSelected()) 
      type = 4; 
     //else if(all.isSelected()) 
      //type = 5; 

     if(single.isSelected()) { 
      digit = 1; 
      System.out.println("single"); 
     } 
     else if(two.isSelected()) 
      digit = 2; 
     else if(triple.isSelected()) 
      digit = 3; 

     if(five.isSelected()) 
      rounds = 5; 
     else if(ten.isSelected()) 
      rounds = 10; 
    } 
} 

}

這裏是主類：

public class Driver { 

public JFrame frame = new JFrame("Math Game"); 

public JPanel screens = new JPanel(new CardLayout()); 

int digit = 1; 
int rounds = 1; 
int type = 1; 

Driver() { 

} 

public void show() { 

    JPanel buttonPanel = new JPanel(); 
    JButton next = new JButton("Next"); 
    JButton previous = new JButton("Previous"); 
    buttonPanel.add(previous); 
    buttonPanel.add(next); 

    Screen1 screen1 = new Screen1(); 
    Screen2 screen2 = new Screen2(); 
    Screen3 screen3 = new Screen3(); 

    screens.add(screen1, "welcome"); 
    screens.add(screen2, "next"); 
    screens.add(screen3, "selection"); 

    frame.add(screens); 
    frame.add(buttonPanel, BorderLayout.PAGE_END); 
    frame.setSize(400, 500); 
    frame.setLocationRelativeTo(null); 
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
    frame.setVisible(true); 

    next.addActionListener(new ActionListener() 
    { 
     public void actionPerformed(ActionEvent ae) 
     { 
      CardLayout cl = (CardLayout)(screens.getLayout()); 
      cl.next(screens); 
     } 
    }); 

    previous.addActionListener(new ActionListener() 
    { 
     public void actionPerformed(ActionEvent ae) 
     { 
      CardLayout cl = (CardLayout)(screens.getLayout()); 
      cl.previous(screens); 
     } 
    }); 
} 

public static void main(String args[]) { 
    SwingUtilities.invokeLater(new Runnable() { 
     public void run() { 
      Driver dr = new Driver(); 
      dr.show(); 
     } 
    }); 
} 

}

我只是嘗試的System.out.println（screen3.getType（））的測試打印;無論是show（）還是主

Answer 1

使用JOptionPane/JDialog其中有modality。

有上How to Make Dialogs

在示例這裏讀JDialog後僅印刷閉合：

public static void main(String[] args) { 
    SwingUtilities.invokeLater(new Runnable() { 
     @Override 
     public void run() { 
      JDialog jd = new JDialog(); 
      jd.setDefaultCloseOperation(JDialog.DISPOSE_ON_CLOSE); 
      jd.setModal(true); 
      jd.pack(); 
      jd.setVisible(true); 

      System.out.println("Here"); 
     } 
    }); 
} 

在這個例子中這裏JOptionPane後僅印刷閉合：

public static void main(String[] args) { 
    SwingUtilities.invokeLater(new Runnable() { 
     @Override 
     public void run() { 
      JPanel panel=new JPanel(); 
      panel.add(new JLabel("Hello, world!")); 

      JOptionPane.showMessageDialog(null, panel, "Panel Message",JOptionPane.PLAIN_MESSAGE); 

      System.out.println("Here"); 
     } 
    }); 
} 

我知道我不應該用Java以線性方式思考，但是我怎樣才能確保在 用戶更改了變量之後獲取變量，而不是之前？

使用模式JDialog/JOptionPane您只需使用公共干將訪問包含的類實例中的變量之後：

public class Test { 
    public static void main(String[] args) { 
     X x= new X();//will only return after dialog closed 

     System.out.println(x.getY()); 
    } 
} 

class X { 

    private int y=0;//will be assigned during dialog/joptionpanes life span 

    public X() { 
     SwingUtilities.invokeLater(new Runnable() { 
      @Override 
      public void run() { 
       //creates and shows the modal dialog/optionpane which will allow modification of variable y through some input/controls 
      } 
     }); 
    } 

    public int getY() { 
     return y; 
    } 
}