I am currently creating this java GUI that will ask the user to input 10 entries, then use the values to execte the next action.
I want only numbers or decimal point to be inputted inside such that it can only be a float value.
If it is not number or decimal point, it should prompt the user to input that specific entry again before the next action is executed.
How should I do it?
Wong,
not sure whether you are using Swing or not...
Ages ago I had the same problem and I solved it with creating a class RestrictedTextField extending JTextField. In the constructor I added a key listener (addKeyListener(new RestrictedKeyAdapter());)
private class RestrictedKeyAdapter extends KeyAdapter {
#Override
public void keyReleased(KeyEvent e) {
if (getText().equals("")) {
oldString = "";
return;
} else {
// if you cannot parse the string as an int, or float,
// then change the text to the text before (means: ignore
// the user input)
try {
if (type.equals("int")) {
int i = Integer.parseInt(getText());
oldString = getText();
} else if (type.equals("float")) {
float f = Float.parseFloat(getText());
oldString = getText();
} else {
// do nothing
}
} catch (NumberFormatException el) {
setText(oldString);
}
// if the text is identical to the initial text of this
// textfield paint it yellow. If the text was changed
// paint it red.
if (initialString.equals(getText())) {
setForeground(Color.YELLOW);
} else {
setForeground(Color.RED);
}
}
}
}
The idea is, that every time the user presses a key in the textfield (and releases it then), the text in the textfield is parsed. If the component should accept only floats for example then the component tries to parse it as an float (Float.parseFloat(..)). If this parsing is successful everything is fine. If the parsing fails (an NumberFormatException is thrown) then the old text is written back into the textfield (literally ignoring the user input).
I think you can add the KeyAdapter directly to the JTextField without creating a dedicated class for that, but with this solution you can remember the initial string and the old string.
you can play around with the code.. you can change the colour of the textfield if the input is valid or not (or like in my code snippet if the text is identical to the initial string).
one additional comment: I set the 'type' of the textfield in a variable with the name 'type', which is simply a String with the values "int", "float", etc.... a better solution would be here for example an enum of course...
I hope this is helpful...
timo
There are various options for what you would like to do. You can check here for one example of doing so. Another example could be to use Formatted TextFields, as shown here.
On the other hand, upon submission, you can try to parse the value to a float or double. If you get any exceptions, then, the value is not a number.
Lastly, you can use Regular Expressions. An expression such as ^\\d+(\\.\\d+)?$ should match any integer or floating point number.
Related
I need to create a program to store all words in an array list. Then check the user input from the textfield to see if it starts with anything other than numbers and punctuation. Otherwise it will need to display an error and prvent the string to be added to the arraylist and display an appropriate error.
https://pastebin.com/8UwDm4nE
Heres the ActionEvent listener that contins the code to check that. Im not really sure how to get it working.
#Override
public void actionPerformed(ActionEvent e) {
for(int i = 0; i < 1; i++) {
String str = tf.getText(); // MUST BE STORED ON AN ARRAY LIST
ta.append(str + "\n"); // Append the text on new line each
if(str.startsWith(String.valueOf(nums))) { // Check input for a number at the start
error.setText("Error: Word starts a number. Please try again!");
error.setForeground(Color.RED);
ta.append("");
} else if (str.startsWith(String.valueOf(punct))) { // Check if input contains a punctuation at the start
error.setText("Error: Word starts with an illegal character. Please try again!");
error.setForeground(Color.RED);
ta.append("");
}
}
}
I'm going to rephrase your problem a bit as clarification, please correct me if I'm misunderstanding.
You have a text field and a text area. You want a user to type a word into the text field and submit it. If that word starts with a number or punctuation, then indicate an error to the user. Otherwise, add it to the text area (on a new line) and the inner ArrayList.
To solve this problem, there are a couple things you'll need:
An ArrayList<String> that is a class member variable where you can store your words
An event handler that handles the button click.
The event handler should:
Parse the string from the text field (using getText(), as you already are).
Do the error checks you're already doing.
If neither of the error conditions are hit (so add an else clause for this), add the word to the text area (which you're already doing) and add it to the ArrayList.
Hopefully this helps you get a clearer idea of how to approach the problem. If not, please post a code sample of what you tried and what error you're specifically running into.
EDIT:
Here is some pseudocode for your if-else error-handling block of code, assuming you declare a new ArrayList to hold your words as a class member:
// as class member variable
List<String> wordList = new ArrayList<>();
// word handler code
if (str starts with a number) {
// handle error
} else if (str starts with punctuation) {
// handle error
} else {
ta.append(str + "\n");
wordList.add(str);
}
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.
Basically I have created an applet that has three textfields one for each of the RGB values. I then created a try catch block to show a dialogue message if the user inputs a string. However, now I want it to find which textfield it was that had a string in it and set only that textfield to null so then they can type an integer, whilst also keeping the values of the two correct textfields.
So for example:
[255] [150] [cat]
step 2: [255] [150] [] (the string textfield should become null)
Code:
try{
if (e.getSource().equals (bttn))
{
as=T1.getText();
ag=T2.getText();
ab=T3.getText();
as=as.trim();
ag=ag.trim();
ab=ab.trim();
redColor= Integer.parseInt(as);
greenColor= Integer.parseInt(ag);
blueColor= Integer.parseInt(ab);
}
}
catch (NumberFormatException exception){
JOptionPane.showMessageDialog(null,"Integers Only","ERROR!",JOptionPane.WARNING_MESSAGE);
}
You have to split your code into tree parts, one for each field.
But this would result in redundant code. To avoid this, you should put the conversion part into a separate function which is called for each field.
I'm new to Java GUI . I'm doing a project using Netbeans.There are several text fields and I need to do validations for them.
Validations should be
Want to check whether fields are empty or not.
If it's a number field it should be validated only to input numbers.
In web (Ex:contact form) validations we can validate the fields step by step when user is entering data up to down. I need to know whether it is possible or not in Java GUI programmes.
Found several methods as Documentfilter,InputVerifier and PlainDocument. Can someone please explain the differences of them and what is the best method to use for validations input data of users in Java?
depending how familiar you are with java programming in general, this helps you more or less
Retrieve the text from the JTextField (getText()) and check for emptiness
Cast the text to a number and catch a NumberFormatException in case its not a number.
for 2) its a validation after the user has entered something and not an validation during typing
You should write java method for validation .
1.Read Text from JTextField using (getText() ) and pass this string to NumberValidation Method . Sample code is shown below
String data=textFieldObject.getText().trim();
boolean validate =isValidMobile(data);//return false if the data is not a valid phone number
public boolean isValidMobile(String PhoneNumber)
{
try{
if(PhoneNumber.length()==10) //checking length.
{
for(int i=0;i<10;i++){
char c=PhoneNumber.charAt(i);
if(!Character.isDigit(c)) //return false if the character is digit
{
return false;
}
}
}else
{
return false;
}
return true;
}catch(Exception r)
{
return false;
}
}
I'm writing an app that takes in an input from the AddBook class, allows it to be displayed in a List, and then allows the user to Search for their book. To this end, I'm creating a temporary EditText, binding it to the box where the user actually enters their search value, then (after ensuring that it is not empty) I compare what they've entered for the ISBN number with the ISBN numbers of each entry in the arrayList of <Book> custom objects, the list being named books.
Problem is, when I try to parse the EditText into an Int, it doesn't seem to work. I first tried using toString() on the EditText, then using Integer.parseInt() on the result of that method, but it hasn't worked out, as the conversion is seemingly unsuccessful;
All of the resources are in place and the code compiles properly, so those aren't the problems here.
EditText myEdTx = (EditText) findViewById(R.id.bookName);
if(myEdTx.getText().equals("")){Toast toast = Toast.makeText(this, "Please enter something for us to work with!", Toast.LENGTH_SHORT);
toast.show();}
else{
//resume here
for(int i=0; i<books.size(); i++)
{
Book tBook = new Book(i, null, null); tBook = books.get(i); String s=myEdTx.toString();
int tInt = Integer.parseInt(s);`
To get the string representation of an EditText's content, use:
String s = myEdTx.getText().toString();
Using toString() directly on the EditText gives you something like:
android.widget.EditText{40d31450 VFED..CL ......I. 0,0-0,0}
...which is clearly not what you want here.
You assume the user inputs a number into the text field, but that is unsafe, as you only get a string text (which theoretically can contain non-numbers as well). When I remember correctly, you can adjust a text field in android where a user only can input numbers, which should suit you more.
NumberFormatException occurs when Integer.parse() is unable to parse a String as integer, so, its better to Handle this exception.
String s = myEdTx.getText().toString();
try {
int tInt = Integer.parseInt(s);
} catch( NumberFormatException ex ) {
//do something if s is not a number, maybe defining a default value.
int tInt = 0;
}
So the current String here you are trying to parse is with white space in the line
and integer class unable to parse that white space. So use following code.
String s=myEdTx.getText().toString();
int tInt = Integer.parseInt(s.trim());
String s = myEdtx.getText().toString().trim();
int iInt = Integer.parseInt(s);