Java 检查空文本框
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Checking of empty textbox
提问by
I am trying to show a messagebox when either the username or password textbox is empty but when I run the project the only textbox showing is "JOptionPane.showMessageDialog(null,"Your Username or Password is incorrect");" Please help and Thank You!
当用户名或密码文本框为空时，我试图显示一个消息框，但是当我运行该项目时，唯一显示的文本框是“JOptionPane.showMessageDialog(null,”您的用户名或密码不正确”)；” 请帮忙，谢谢！
private void jButton1ActionPerformed(ActionEvent evt) {
String user=txtUsername.getText();
char[] pass=txtPassword.getPassword();
if(user == null) {
JOptionPane.showMessageDialog(null,"Username Field is empty");
} else if(pass==null) {
JOptionPane.showMessageDialog(null,"Password Field is empty");
} else {
String sql="select * from account where username=? and password=?";
try{
pst=conn.prepareStatement(sql);
pst.setString(1,txtUsername.getText());
pst.setString(2,txtPassword.getText());
rs=pst.executeQuery();
if (rs.next()) {
GridlockMain a=new GridlockMain();
a.setVisible(true);
} else {
JOptionPane.showMessageDialog(null,"Your Username or Password is incorrect");
txtUsername.setText(null);
txtPassword.setText(null);
}
} catch (SQLException e) {
JOptionPane.showMessageDialog(null,e);
}
}
}
回答by Masudul
JTextField.getText()does not return nullif you keep it empty. Try to check value using isEmptymethod at ifcondition.
JTextField.getText()null如果您将其保留为空，则不会返回。尝试isEmpty在if条件下使用方法检查值。
String user=txtUsername.getText();// It return empty String ""
// even no data is entered.
if(user.isEmpty){
JOptionPane.showMessageDialog(null,"Username Field is empty");
}
......
回答by subash
try this..
尝试这个..
if(!user.length() > 0){
JOptionPane.showMessageDialog(null,"Username Field is empty");
}
else if(!pass.length > 0){
JOptionPane.showMessageDialog(null,"Password Field is empty");
}
回答by Bilbo Baggins
It returns an empty string "" compare the
它返回一个空字符串 "" 比较
StringUtils.isEmpty(txtUsername.getText())
回答by Ali Asghar Ataie
if (user.length() == 0) {
JOptionPane.showMessageDialog(null, "Username Field is empty");
} else if (pass.length() == 0) {
JOptionPane.showMessageDialog(null, "Password Field is empty");
}
回答by WhiteFringe
I also struggled with the text Validation process. I found a very easy way to test this. Here, instead of using JOptionPaneto show a message to the user, I just didn't allow them to enter, or press the button. Here's my code:
我也在文本验证过程中挣扎。我找到了一个非常简单的方法来测试这个。在这里，JOptionPane我没有使用向用户显示消息，而是不允许他们进入或按下按钮。这是我的代码：
//Validate whether user Has input some information:
if(UserNameTA.getText() == null || UserNameTA.getText().trim().isEmpty())
{
btnEnter.setEnabled(false);
}
else
{
//Make a new JFrame for login
new ProfileHome().setVisible(true);
frame.dispose();
}
btnEnter.setEnabled(true);
I hope this at least guides you to your success.
我希望这至少能引导你走向成功。
回答by Gorgatz M
String user = txtUsername.getText();
String pw = txtPassword.getText();
if(user.isEmpty() || (pw.isEmpty()))
{
JOptionPane.showMessageDialog(null, "Your Username or Password is incorrect" );
}
else
{
//proceed to query
