java - JOptionPane 取消按钮和获取输入

Question

我试图让用户输入那里的名字，如果它留空，它会再次询问，如果他们填写它，它会设置一个 JLabel 或点击取消退出。
我的最后一个 if 语句是错误的，它不喜欢 nameEnt。

public Player() {
    //setBackground(Color.green);
    setSize(600, 400);
    name = new JLabel();//Input hint
    JOptionPane nameOption = new JOptionPane();
    String nameEnt = nameOption.showInputDialog("First Name: ");
    if (!nameEnt.matches("[a-zA-Z]+")) {
        name.setText(nameEnt);
    }
    if (nameEnt.length() == 0) {
        //if this condition is true JOption stays until name is entered or canceled 
    }
    if (nameEnt == nameOption.CANCEL_OPTION) {
        System.exit(0);
    }
}

Answer 1

JOptionPane.CANCEL_OPTION 是一个静态 int 字段，您不能将 String 与 int 与 ==.

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良好做法

在你的情况下，你想一次性使用确定和取消按钮 JOptionPane.showConfirmDialog 和 JOptionPane.showInputDialog() 这是不可能的，我建议使用这个代替:

JTextField nameF = new JTextField(20);//create TextField

JPanel myPanel = new JPanel();//cerate JPanel
myPanel.add(new JLabel("Name"));
myPanel.add(nameF);//add your JTextField to your panel

int result;
do {
    result = JOptionPane.showConfirmDialog(null, myPanel,
            "Title of Panel", JOptionPane.OK_CANCEL_OPTION);//add your panel to JOptionPane
    if (result == JOptionPane.OK_OPTION) {//if the user press OK then
        if (nameF.getText().isEmpty()) {//check if the input is empty
            //if this condition is true JOption stays until name is entered or canceled 
        } else if (!nameF.getText().matches("[a-zA-Z]+")) {//check if the input match with your regex
            //name match exactly
            //name.setText(nameF.getText());
        }
    }
} while (result != JOptionPane.CANCEL_OPTION);//If the user hit cancel then exit