Is there some way to detect if a JTextField is deselected, i.e. the field WAS selected but now you have selected something else. The reason why I want to do this is because I want to check my users forms for any illegal characters before they try to submit their data. If there is some easier way to do that, instead of the way I'm trying to solve it, I'll gladly accept enlightenment.
At first though use a FocusAdapter and override focusLost(FocusEvent fe) which will be called when JTextField loses focuses, i.e another component is selected.
However because you have a purpose:
I want to check my users forms for any illegal characters before they
try to submit their data
Id suggest a read on How to Use the Focus Subsystem - Validating Input
Better options than a FocusAdapter - tailored made for validating/restricting user input:
DocumentFilter. See here and this variation for an example.
InputVerifier. See here for an example
JFormattedTextField. See here for an example
Related
I know there are many questions on how to focus on a certain text field and so on, but it seems that the issue I am facing is a bit different. So, I have a JTextField which has functionality to autocomplete the text if something that is currently in it has been typed before by the user. I also have a set of buttons that perform insertion of some predefined portion of text into the text field when pressed. The problem is that every time any new text appears in the text field, the autocomplete can trigger and append the text that was used by the user previously. In order to it more friendly, I decided to select the part appended by the autocomplete. All the code is executed in the ED thread. Consider the case when the text field was not in focus :
Both code samples are in the actionPerformed method of the button.
// does not work
if (textField.requestFocusInWindow()) {
textField.getDocument().insertString(...);
}
The insertString() is overriden and has all the logic to select appended string by the autocomplete. So, the only thing I need is that the text field is selected before the string is inserted.
I tried :
// does work
textField.requestFocusInWindow();
SwingUtilities.invokeLater(() -> {
textField.getDocument().insertString(...);
});
The official doc says :
The call to the requestFocusInWindow method initiates the focus transfer, but it does not immediately move the focus ...
This sort of makes sense, since to acquire the focus, a call must be made to the window manager of the clients operating system (that's how I understand that, correct me if I am wrong).
Is the second example working mainly because both events (getting focus and inserting the string) are added to the event queue and the insertion appears after the focus request (actually at the end of the queue) or am I missing something? Is it a valid solution? Can it be done better?
Note: simply adding a listener to the text field ( to react when it is in focus) is not a solution, since the logic I described here is only a part of the whole functionality used.
I'm (a beginner) creating a sign up form in netbeans. What I really want to happen is, a JOptionPane will appear when the textfield loses focus if a users input is wrong . I've been searching for the answer on the internet for the whole day but the answers I find don't satisfy me.
You need to implement a FocusListener, add it to your textField and in your focusLost implementation of the FocusListener you need to do whatever you want it to do when focus is lost.
http://docs.oracle.com/javase/tutorial/uiswing/events/focuslistener.html
I'm not experienced with NetBeans but I'm assuming you use the graphical tool to create your form. I think you will need to start coding to implement the listener.
You should be using an InputVerifier for this type of validation.
I will do my best to explain-- I am trying to make a choose-your-own-adventure type game while using a TextField and a TextArea, where what is written in the TextField is appended into the TextArea (this I know how to do via ActionListener).
However, I need to have the TextArea start with a pre-written 'intro', which asks the user at the end if they want to continue or not. Therefore, I need it to be able to scan the user's response ('yes' or 'no') and choose the appropriate selection of pre-written text to follow.
I don't want to overwrite what is already in the TextArea, I want to add to it. I suppose what I'm confused about it how I'm supposed to lay out the entire file so that it functions properly, because the different choices for the adventure span different methods. Having
"String text = textField.getText();" only within the actionPerformed method means I can't use 'text' elsewhere, but moving that line up with my other variables tells me it can't reference the field before it's defined.
I am fairly new to Java and am working on this as a project for a non-programming school course. I've been through many iterations thus far and this is what seems to be my final attempt, as I've remade it repeatedly and don't have much time left. :(
Your questions/comments and my attempts to answer:
I am trying to make a choose-your-own-adventure type game while using a TextField and a TextArea, where what is written in the TextField is appended into the TextArea (this I know how to do via ActionListener).
As per my comment, be sure to create a Swing GUI which would use a JTextField and a JTextArea. You would then add your java.awt.event.ActionListener to the JTextArea, and the ActionListener would respond whenever the user pressed <ENTER> within the JTextField.
However, I need to have the TextArea start with a pre-written 'intro', which asks the user at the end if they want to continue or not. Therefore, I need it to be able to scan the user's response ('yes' or 'no') and choose the appropriate selection of pre-written text to follow.
This can be done easily, but sounds as if you may be trying to shoe-horn a linear console type program into a GUI. If so, consider reconsidering your program design since what works best for one often doesn't work well for another. If you do re-write, then you should consider redoing most including your program flow, but excepting perhaps the "model" portion of your previous program, the "business logic" that underlies everything.
I don't want to overwrite what is already in the TextArea, I want to add to it. I suppose what I'm confused about it how I'm supposed to lay out the entire file so that it functions properly, because the different choices for the adventure span different methods. Having "String text = textField.getText();" only within the actionPerformed method means I can't use 'text' elsewhere, but moving that line up with my other variables tells me it can't reference the field before it's defined.
Again as per comments a JTextArea has an append(String text) method that will add new text to existing text that is already displayed in your JText Area. So on that note, your ActionListener's actionPerformed method could be very simple and look something like:
public void actionPerformed(ActionEvent e) {
String text = textField.getText();
textArea.append(text):
}
Although you may need to add line feeds, "\n" either before and/or after the text you are going to append.
In my application I have a JTextField that will only allow the user to fill it with input formatted in a certain way. I have a method that checks if input into the field is valid and if not it displays a dialog. After this occurs I would like the focus to return to the text field so that the user can correct there mistake and type in the appropriately formatted input. I tried to do this by having the JTextField call requestFocus() on itself but this seems to only half work. The JTextField displays the flashing cursor but I cannot actually type in any text until I click on the text field again. Is there another method I need to call? I could not find anything else in the documentation.
It's not exactly the solution you asked for, but you might want to look at javax.swing.InputVerifier. This object allows you to verify the input to a field and prevent taking focus away from it if the format isn't right. I don't think it would allow you to put up a dialog explaining the error (though it might - try it) but it would certainly allow you to put a message in a 'message area'.
What you do is set an InputVerifier on the JComponent, have it test the contents for validity; if it isn't right then the JComponent won't release focus (and can write an error message).
I have a Swing JComboBox with an InputVerifier set correctly.
I am using the combo box to set an integer.
If I type "cat" in the field and hit tab, my InputVerifier triggers and resets the value to "0".
If I type "cat" and hit enter, my InputVerifier is never called from actionPerformed. Do I need to explicitly call my InputVerifier from actionPerformed?
What's the best model to validate my JComboBox on tab and enter? It seems like this is something that should be given to me "for free" by the swing model.
The problem is "hit Tab" and "hit Enter" mean two different things in Java Swing. But those two actions mean the same thing to you, me, and the user.
Swing has no single mechanism to detect "when the user is done entering data". Instead, Swing focuses on the mechanics of "is this field losing keyboard focus" and "is the user pressing Enter key while inside a field".
Semantically those two actions mean the same thing from the user's perspective: "I'm done. Here's my input.". But, from what I can tell, Swing fails to offer a way to detect that user intention. I'm as surprised as you by the lack of such a feature, as this seems to be the most basic function of a form in a GUI. What we need, but don't have, is a "dataEntered" event.
There is a workaround…
In a similar context (JTextField instead of JComboBox) the Sun/Oracle Java Tutorial provides the example InputVerificationDemo where a class is created that:
Extends InputVerifier (to handle tabbing/clicking where focus is about to be lost)
Implements ActionListener (to handle pressing Enter key without leaving field)
The good thing about this workaround is that you can locate your handling code all in one place. The downside is that you still have the hassle of:
Creating a separate class.
Instantiating that class.
Passing that instance to both the setInputVerifier and addActionListener methods of your widget (JTextField, etc.).
This is the expected behavior of InputVerifier: the TAB key attempts to change focus, while the ENTER key does not. You can bind the ENTER key to a different action, as described in the tutorial How to Use Key Bindings. Also, consider the informative article Key Bindings, which includes a handy utility application.
When using an editable combo box, focus is on a JTextField which is used as the editor of the combo box. You can add an ActionListener to this text field.
In the ActionListener you could try invoking the transferFocus() method which should be equivalent to tabbing our of the text field. If that doesn't work then tha actionListener should invoke the same editing code as the InputVerifier.