I have a program, that whenever you type something and hit enter, it prints it out in a window (it's basically a command prompt). However, due to a few problems with a calculator function I'm trying to add, if the user input is a number, I want it to totally ignore it
input = new JTextField();
input.setEditable(true);
input.setForeground(Color.WHITE);
input.setCaretColor(Color.WHITE);
input.setOpaque(false);
input.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent e) {
String text = input.getText();
if (text.length() >= 1){
print(text + "\n", false);
doCommand(text);
scrollBottom();
input.selectAll();
}
}
});
You could check if text is a number with a regex like that:
text.matches("[1-9][0-9]*");
I hope it helps.
Related
I am trying to retrieve the values from a JTextField on a keypress to do something if the values are integers and to clear the field if the values are not integers. Every time I try to retrieve the value, I am getting the value entered before that(if I enter 12 I get 1 back then if I enter 123 I get 12 back) and when I try to clear the field on an invalid character everything but the invalid character gets cleared?
public void setUpListeners()
{
JTextField jT [] = myV.getTextFields();
jT[0].addKeyListener(new KeyAdapter(){
public void keyTyped(KeyEvent e){
int id = e.getID();
if (id == KeyEvent.KEY_TYPED)
{
char c = e.getKeyChar();
try
{
//check if chars entered are numbers
int temp = Integer.parseInt(String.valueOf(c));
String tempS = jT[0].getText();
System.out.println(tempS);
}
catch(Exception ex)
{
jT[0].setText("");
System.out.println("Not an integer");
}
}
}
});
}
You could do the following:
public static boolean validateNumber(char num){
return (num >= '0' && num <='9');
}
And then use parameter KeyEvent "e":
if(!validateNumber(e.getKeyChar()))
e.consume();
And instead of using
public void keyTyped(KeyEvent e){
use
public void keyReleased(KeyEvent e){
I think you will get what you need, I hope I have helped you ;)
Swing components use Model-View-Controller (MVC) [software] design pattern / architecture. The model holds the data. For a JTextField the data is the text it displays. The default model for JTextField is PlainDocument, however JTextField code actually refers to the Document interface which PlainDocument implements.
Look at the code for method getText() in class JTextComponent (which is the superclass for JTextField) and you will see that it retrieves the text from the Document.
When you type a key in JTextField, the character gets passed to the Document. It would appear that your keyTyped() method is invoked before the character you typed reaches the Document, hence when you call getText() in your keyTyped() method, you're getting all the text apart from the last character you typed.
That's one of the reasons not to use a KeyListener in order to validate the text entered into a JTextField. The correct way is detailed in the question that tenorsax provided a link to in his comment to your question.
Apart from DocumentFilter or JFormattedTextField (or even InputVerifier), you can add an ActionListener to JTextField which will execute when you hit Enter in the JTextField. You will find many on-line examples of how to implement each one of these options, including the link provided in tenorsax comment.
I am writing a BMI calculator application. Currently an error happens which causes the program to stop working if I do not enter data into one field. For instance, there are two JTextFIelds for 'height', one being feet and the other inches. If I just input '6' into the feet JTextField and enter nothing into inches JTextField, then enter my weight in the weight JTextField and click on calculate, it does not work.
What I want to do is display a message dialog saying "Please make sure all fields are filled in" if one field does not contain data.
Below is the ActionHandler code that is added to my 'Calculate' button.
public void actionPerformed(ActionEvent e) {
double heightFT = ((Double.parseDouble(heightFt_TF.getText()));
double heightIn = (Double.parseDouble(heightIn_TF.getText()));
double weight = (Double.parseDouble(weight_TF.getText()));
double totalHeight = (heightFT*12) + heightIn;
BMI = (weight / (totalHeight*totalHeight)) * 703;
String s = BMI+"";
s = s.substring(0,4);
BMI_TF.setText(s);
}
Solved
I have now fixed the problem. What I did was add 'throws NumberFormatException' in the method and did a try catch. In the try code block I wrote the code I want to execute if all data fields are entered. In the catch clause I wrote code that uses the NumberFormatException and simply displays the message dialog with the error message. Now, if one field is not entered, the message dialog appears!
Just check if your JTextField objects contain text.
E.g:
if (heightFt_TF.getText() == null || heightIn_TF.getText() == null || weight_TF.getText() == null) {
JOptionPane.showMessageDialog(null, "Please make sure all fields are filled in");
}
Of course you also have to make sure, that the content of the textfields really contains a number.
Download Apache Commons Lang library and use StringUtils.isBlank(myTextField.getText()); to validate your fields.
public boolean validateFields() {
if (StringUtils.isBlank(heightFt_TF.getText()) {
// show message
return false;
}
if (StringUtils.isBlank(weight_TF.getText()) {
// show message
return false;
}
return true;
}
Only run your calculation if validateFields() returns true.
public boolean validate(JTextField field) {
boolean result = field.getText() != null;
if (result) {
try {
Double.parseDouble(field.getText()));
} catch(NumberFormatException e) {
result = false
}
}
return result;
}
I put a KeyListener on a TextField in my swing application to try some functionalities. The goal is to react on every key typed in that TextField. The user should only type in numbers, but how it is, it is possible to enter alphabetical chars too. So additionally I have to check every time after a key is typed, if the whole thing is a number, if so, make something with that number, if not, tell the user there is an error without exit the program. So I want to do something like this:
String enteredNumPlayers = "";
JTextField textfieldNumPlayers = new JTextField();
textfieldNumPlayers.setBounds(/*some values*/);
textfieldNumPlayers.setBorder(BorderFactory.createMatteBorder(0, 0, 1, 0, Color.DARK_GRAY));
textfieldNumPlayers.setHorizontalAlignment(JTextField.CENTER);
textfieldNumPlayers.addKeyListener(new KeyListener() {
#Override
public void keyTyped(KeyEvent e) {
if(e.getKeyChar()!=/*Code of the back key*/){
enteredNumPlayers += e.getKeyChar();
System.out.println(e);
}else{
enteredNumPlayers = enteredNumPlayers.substring(0, s1.length()-1);
}
try{
Integer.parseInt(enteredNumPlayers);
// do something with that number
}catch (NumberFormatException err){
new ErrorDialog("Not a number"); // my own method to allude user
}
}
#Override
public void keyReleased(KeyEvent e) {
// TODO Auto-generated method stub
}
#Override
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
}
});
Now I wanted to look whats the specific Code for the back key by simply System.out.println(e) in the keyTyped(...) method, but following get printed:
java.awt.event.KeyEvent[KEY_TYPED,keyCode=0,keyText=Unbekannt keyCode: 0x0,keyChar=Rücktaste,keyLocation=KEY_LOCATION_UNKNOWN,rawCode=0,primaryLevelUnicode=0,scancode=0,extendedKeyCode=0x0] on (...)
why is every key value or code = 0 or unknown? Shouldn't it be the ascii value? Using "Rücktaste" would also be ugly, since on a english working computer this value would be different, isn't it? So how can I cleanly check if the key typed is the back key?
The same thing happens with other characters, except that their keyChar is the right one.
What you are looking for is a DocumentFilter, DocumentListener or a JFormattedTextField. All three of them are a better solution then using a key listener as it also covers drag-and-drop, copy-paste or any other mechanism you can think of to put text into a textfield.
I think that having an error message to show each time the user presses anything but an integer is a bit annoying. Check this sample code that uses a regular expression to match the input and has the advantage of accepting only digits, anything else is just not inserted to the textfield (managed by overriding the insertString method of PlainDocument).
I have a String named updatedDisplay that is set to empty in the constructor.
The buttons[] are JButtons and alarmCode is a String field.
I want the user to press four buttons (and they should be concatenated and stored in the updatedDisplay field).
The checkCode() method is executed to try match updatedDisplay against alarmCode. Trouble is, they never match. I think it may be something to do with a "space" when I originally declare my updatedDisplay as follows:
private String updatedDisplay = " ";
The updatedDisplay field doesn't seem to be storing the e.getActionCommand() value.
//add actionListeners to each button (except the "clear" button) to display value on screen
for (int i = 0; i< (buttons.length -1); i++) {
buttons[i].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
//store the name of the button in a local variable
String command = e.getActionCommand();
System.out.println("You clicked " + command);
updatedDisplay = updatedDisplay + command;
//updatedDisplay = command;
System.out.println (updatedDisplay);
screen.setText(updatedDisplay);
}
});}
I have an armButton that, when pressed, should trigger the checkCode() method. The method checks if updatedDisplay and alarmCode are equal:
//add actionListener to the arm button
armButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e)
{
checkCode();
}
});
checkCode():
public void checkCode() {
//check if user entered the correct code
if (updatedDisplay == alarmCode)
{
updatedDisplay = "System Armed!";
screen.setText(updatedDisplay);
}
else
{
updatedDisplay = "Incorrect Code, Try again!";
screen.setText(updatedDisplay);
}
}
Even when I output the button presses to the terminal window they look right - but as I said, I suspect a "space" is being entered at the start.
Any ideas?
Solution
Try:
if( updatedDisplay.equals( alarmCode ) { // ...
Comparison
To understand this, read:
http://leepoint.net/notes-java/data/expressions/22compareobjects.html
Summary
Since updatedDate and alarmCode are object references, you must ask the objects to compare their values. You can think of them as pointers whose values are locations in memory that contain strings. Rather than comparing the value of the pointers (references), you want to compare the text that starts at that memory location.
I have a calculation application which I need to validate the fields to check if the values entered are numeric numbers and not alphanumeric. I have some ideas about the codes.
Please guide me if I have done anything wrong or seem noob as this is my first time trying out Swing.
private void jTextField1ActionPerformed(java.awt.event.ActionEvent evt) {
String text1 = jTextField1.getText(); // TODO add your handling code here:
}
private void jTextField2ActionPerformed(java.awt.event.ActionEvent evt) {
String text2 = jTextField2.getText(); // TODO add your handling code here:
}
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
if (text1 and text2 != <numeric number>){
JOptionPane.showConfirmDialog(null, "Please enter numbers only", "naughty", JOptionPane.CANCEL_OPTION);
}
// First we define float variables.
float num1, num2, result;
// We have to parse the text to a type float.
num1 = Float.parseFloat(jTextField1.getText());
num2 = Float.parseFloat(jTextField2.getText());
// Now we can perform the addition.
result = num1+num2;
// We will now pass the value of result to jTextField3.
// At the same time, we are going to
// change the value of result from a float to a string.
jTextField3.setText(String.valueOf(result));
// TODO add your handling code here:
}
Please do help. By the way why does my NetBeans keep informing me that it does not recognize the "JOptionPane" Command?
Float.parseFloat() will throw a NumberFormatException if the String isn't numeric and cannot be parsed into a Float. You can add a try-catch block to check for this condition:
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
float num1, num2, result;
try {
num1 = Float.parseFloat(jTextField1.getText());
num2 = Float.parseFloat(jTextField2.getText());
result = num1+num2;
jTextField3.setText(String.valueOf(result));
} catch (NumberFormatException e) {
JOptionPane.showConfirmDialog(null, "Please enter numbers only", "naughty", JOptionPane.CANCEL_OPTION);
}
}
If alphanumeric input is not valid for the Swing component in the first place, then instead of validating this post-entry, you should restrict the component to accept only certain format in the first place.
Using the formatters that Swing provides, you can set up formatted text fields to type dates and numbers in localized formats. Another kind of formatter enables you to use a character mask to specify the set of characters that can be typed at each position in the field. For example, you can specify a mask for typing phone numbers in a particular format, such as (XX) X-XX-XX-XX-XX.
That said, you can, among other things, use Integer.parseInt(String s) to see if an arbitrary string can be parsed into an int; the method throws NumberFormatException if it can't. There are also Double.parseDouble, etc.
See also
Java Tutorials/Swing/How to use Formatted Text Field
How to use the Focus Subsystem/Input Validation
Java Tutorials/Internationalization/Formatting - Numbers and Currencies
Related questions
A simple way to create a text field (or such) that only allows the user to enter ints/doubles in Java?
A textbox class only accept integers in Java
Validating an integer or String without try-catch - java.util.Scanner option
try {
Integer.parseInt(foo);
} catch (NumberFormatException e) {
// Naughty
}
Try this:
String temp = txtField.getText();
try
{
int val = Integer.parseInt(temp);
}
catch(NumberFormatException e) {
System.out.println("Invalid");
}
To make it more enjoyable, use JOptionPane (makes it more more interactive)
textFieldCrDays = new JTextField();
textFieldCrDays.addKeyListener(new KeyAdapter() {
//// validate onlu numeric value
public void keyTyped(KeyEvent e) {
if (textFieldCrDays.getText().length() < 3 && e.getKeyChar() >='0' && e.getKeyChar() <= '9')
{
// Optional
super.keyTyped(e);
}
else
{
// Discard the event
e.consume();
}
}
});
A relatively old question, but I figured I would take a shot at it, to maybe help out the random Google Searches.
Another approach someone could take to minimise code and reduce the number of additional classes is to add a KeyListener for the keyType event and check for the Char value. This isn't very portable (you can't use region specific formatting such as numerical punctuation), but this could be quite helpful for straight integers.
You could also do a relative length here as well:
textField.addKeyListener(new KeyAdapter()
{
#Override
public void keyTyped(KeyEvent keyEvent)
{
if (textField.getText().length() < 3 && keyEvent.getKeyChar() >= '0' && keyEvent.getKeyChar() <= '9')
{
// Optional
super.keyTyped(keyEvent);
}
else
{
// Discard the event
keyEvent.consume();
}
}
});
You can also add another event listener to validate the entire integer for further processing (the entire number must be > 800 and < 5220 for example).
A good place for this would be on the focusLost event(?).
If you are doing these features frequently, it would be best to subclass the JTextField class to provide this functionality.
EDIT: Using Character.isLetter(keyEvent.getKeyChar()) is even more clear.