Java Textfield getText（）不等待用户输入

Question

I have a String called temp that is set to "void" to begin with. I want the while statement to wait for the user to enter some characters in the text box before re evaluating the while loop? Currently, it prints "Enter Data" then just continues to set the value of temp to null. How would I go about trying to do this?

String temp = "VOID";

while(UserScreen.textField.getText().equals("") && temp == "")
{
    UserScreen.messageAppend("Enter data");
    temp = UserScreen.textField.getText();
    UserScreen.messageAppend(temp);    
}

Answer 1

The getText() method of textfield your using isnt a blocking method, and will thus be executed as soon as it is called. Your best bet would most likely be to attach a listener to the textfield, for example:

textField.addActionListener(new ActionListener() {
  public void actionPerformed(ActionEvent e) {
      temp = UserScreen.textField.getText();
      UserScreen.messageAppend(temp);    
  }
});

The listener gets called when you press enter. If you need to listen for every single change in the textfield then use a documentListener instead:

textField.getDocument().addDocumentListener(new DocumentListener() { ... });

Answer 2

With JTextField you can use an KeyListener for receiving keyboard events (keystrokes). Something like this:

KeyListener keyListener = new KeyListener() {
  public void keyPressed(KeyEvent keyEvent) {
    // here you validation
  }
}
nameTextField.addKeyListener(keyListener);

Also the Temp is VOID therefore should be temp.equals("VOID")

while(UserScreen.textField.getText().equals("") && temp.equals("VOID"))