如何在JavaSwing中获取JTextField的值?
我有一个JTextField和一个JButton。我试图在用户单击按钮时获取文本字段中的用户类型如何在JavaSwing中获取JTextField的值?,java,swing,jbutton,jtextfield,Java,Swing,Jbutton,Jtextfield,我有一个JTextField和一个JButton。我试图在用户单击按钮时获取文本字段中的用户类型 public String insideTextField; public void login() { loginFrame = new JFrame("Test"); loginFrame.setIconImage(imageIcon.getImage()); loginFrame.setSize(400,400); loginFrame.setLayout(
public String insideTextField;
public void login() {
loginFrame = new JFrame("Test");
loginFrame.setIconImage(imageIcon.getImage());
loginFrame.setSize(400,400);
loginFrame.setLayout(new GridLayout(12, 3));
loginFrame.add(usernameField);
loginFrame.add(loginButton);
loginButton.addActionListener(e -> {
insideTextField = usernameField.getText();
loginFrame.setVisible(false);
});
loginFrame.setVisible(true);
}
我希望insideTextField
是我调用此方法后用户在文本字段中键入的内容。但它是空的。但是,loginFrame
将被隐藏,因为loginFrame.setVisible(false)代码>所以按钮可以工作了
我做错了什么?你的期望包含着神奇的思维。请理解insideTextField
包含一个字符串对象,该对象实际上是不可变的(不能更改)。是的,当您创建insideetextfield
时,您会为它分配恰好位于JTextField中的字符串,很可能是一个空的“
字符串,但是请理解,当JTextField的文本属性更改时,insideetextfield
不会更改,事实上不能自行神奇地更改。解决方案是not有一个insideTextField
字段,而是给类一个getter方法,在需要时提取JTextField中的当前字符串。例如:
public String getUserName() {
return usernameField.getText();
}
旁注:我通常使用模态JDialog而不是JFrame来获取登录凭据。这样,因为对话框是模态的,所以我知道用户何时使用它。事实上,JOptionPane可以作为一个快速而肮脏的模式对话框创建者。例如,如果我们有这样一个登录JPanel:
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.BorderFactory;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JPasswordField;
import javax.swing.JTextField;
@SuppressWarnings("serial")
public class LoginPanel extends JPanel {
private static final int GAP = 3;
private JTextField usernameField = new JTextField(10);
private JPasswordField passwordField = new JPasswordField(10);
public LoginPanel() {
setLayout(new GridBagLayout());
GridBagConstraints gbc = getGbc(0, 0);
add(new JLabel("User Name:"), gbc);
gbc = getGbc(1, 0);
add(usernameField, gbc);
gbc = getGbc(0, 1);
add(new JLabel("Password:"), gbc);
gbc = getGbc(1, 1);
add(passwordField, gbc);
setBorder(BorderFactory.createEmptyBorder(GAP, GAP, GAP, GAP));
}
private static GridBagConstraints getGbc(int x, int y) {
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = x;
gbc.gridy = y;
gbc.fill = GridBagConstraints.HORIZONTAL;
gbc.weightx = 1.0;
gbc.weighty = 1.0;
gbc.insets = new Insets(GAP, GAP, GAP, GAP);
gbc.anchor = x == 0 ? GridBagConstraints.WEST : GridBagConstraints.EAST;
return gbc;
}
public String getUserName() {
return usernameField.getText();
}
public char[] getPassword() {
return passwordField.getPassword();
}
}
同样,使用getter方法提取JTextField中的文本,我们可以在JOptionPane中显示它,如下所示:
JFrame frame = new JFrame("LoginExample");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
// fill the JFrame with the main GUI
// ....
frame.pack();
// create the LoginPanel JPanel here
LoginPanel loginPanel = new LoginPanel();
// and display it in a JOptionPane here
int result = JOptionPane.showConfirmDialog(frame, loginPanel,
"User Log-In", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
if (result == JOptionPane.OK_OPTION) {
String userName = loginPanel.getUserName();
char[] password = loginPanel.getPassword();
// test to make sure code is working
System.out.println("User Name: " + userName);
// check for name/password validity here
// ... if name/password OK, then show JFrame:
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
发布一个完整的最小示例,再现问题并显示问题:您发布的代码从未对InsideTextField执行任何操作请参见要回答的编辑