how to insert characters at particular index in JFormattedTextField of MaskFormatter in Java?

问题

I have a string which is say "AAAABB". I have a JFormattedField of MaskFormatter. so I have ? ? ? ? ? ? in my Frame. I have two buttons A and B. when the user presses A button, the JFormattedField of the MaskFormatter should replace ? with Letter A for all occurrences of A. i.e, index 0,1,2,3 in this example.

I have my code that gets the list of indices to be replaced with A. But I am having difficulty in implementing setLetter(String Letter, int Position) method, that takes letter and indices to be replaced in the JformattedField. example if I pass setLetter("A",2), I should get ? ? A ? ? ? in the above example. Please try this code to see the frame.

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.ParseException;
import java.util.ArrayList;

import javax.swing.JButton;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.text.MaskFormatter;

public class TestMain extends JPanel{

    JFormattedTextField input;

    private MaskFormatter formatter;

    public final String WORD = "ABBAABBA";

    public TestMain() {
        try {
            JLabel label = new JLabel("Guesss");
            String s="";
            for (int i =0;i<WORD.length();i++){
                s+="? ";
            }
            formatter = new MaskFormatter(s);
            formatter.setPlaceholderCharacter('?');
            input = new JFormattedTextField(formatter);
            input.setColumns(20);
            add(label);
            add(input);
        } catch (java.text.ParseException exc) {
            System.err.println("formatter is bad: " + exc.getMessage());
            System.exit(-1);
        }
        JButton buttonA = new JButton("A");
        JButton buttonB = new JButton("B");

        buttonA.addActionListener(clickedbutton());
        buttonB.addActionListener(clickedbutton());

        add(buttonA);
        add(buttonB);
    }

    private ActionListener clickedbutton() {
             return new ActionListener() {
                 public void actionPerformed(ActionEvent e) {
                    JButton pressedButton = (JButton) e.getSource();
                    String letter = e.getActionCommand();
                    try {
                        //System.out.println("actionCommand is: ---" + letter);

                        //Get the list of indices
                        int index = WORD.indexOf(letter);
                        ArrayList<Integer> indices = new ArrayList<Integer>();
                        if (index>=0){
                            for(int j=0;j<WORD.length();j++){
                                if (WORD.charAt(j)==letter.charAt(0)){
                                    indices.add(j);
                                }
                            }
                            //System.out.println(indices);
                        }
                        for (int k =0 ; k < indices.size(); k++){
                            setLetter(letter, k);
                        }

                    } catch (ParseException e1) {
                        // TODO Auto-generated catch block
                        e1.printStackTrace();
                    }
                 }
                 };
         }

    public void setLetter(String letter, int position) throws ParseException {
        String word="Hello";
        input.setValue(letter);
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame();
        TestMain tm = new TestMain();
        frame.add(tm);
        frame.pack();
        frame.setTitle("formatter");
        frame.pack();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

}

回答1:

I don't think a mask formatter is what you want for this because you aren't really formatting a string here. If you just want to take a string and set characters at certain positions you should formulate the string yourself.

String text = "";

for (int i = 0; i < WORD.length(); i++) {
    if (String.valueOf(word.charAt(i)).equals(letter)) {
        text += letter + " ";
    } else {
        text += "? ";
    }
}

input.setText(text);

Also a style note: all caps is for identifiers of static variables.

来源：https://stackoverflow.com/questions/19458286/how-to-insert-characters-at-particular-index-in-jformattedtextfield-of-maskforma

标签

java

swing

formatter

jformattedtextfield