我在理解如何使用actionlistener来改变变量的值时遇到了问题。
在我的程序中，我需要通过选择一些单选按钮来存储用户做出的选择。
我有一个带有卡片布局的主类，然后是几个类，每个类都是不同的面板。在其中一个面板中，我有一些单选按钮，actionlistener作为内部类。
当我尝试在主类中打印变量值时，会在用户做出选择之前立即打印它，因为我实例化面板类并从中获取变量我在变量发生之前得到变量由用户。
我知道我不应该以线性的方式思考Java，但是如何确保在用户更改变量之后才获取变量而不是之前？我将无法做到这一点吗？我知道我的想法存在一些缺陷，但我已经多年没睡好了，我只是无法理解这一点。
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;
}
}
}
这是主要课程：
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();
}
});
}
}
我只是尝试System.out.println的测试打印（screen3.getType（））;在show（）或main
中答案 0 :(得分：3)
使用JOptionPane / JDialog，其modality。
在示例中此处仅在JDialog关闭后打印：
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");
}
});
}
在此示例中此处仅在JOptionPane关闭后打印：
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");
}
});
}
我知道我不应该用Java来线性思考，但我怎么能这样做 确保我在变量被变换后获取变量 用户而不是之前？
使用模态JDialog / JOptionPane之后，您只需使用公共 getters 来访问类实例中包含的变量：
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;
}
}