Question

我正在尝试将jtextfield限制为不接受空格作为其第一个字符。我的代码已经限制了jtextfield不接受第一个输入作为空格，但是当我输入一个字母然后擦除字段的限制而不接受空格不起作用时我就卡住了

public class Restriction {

    public Restriction() {
        initComponents();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Restriction();
            }
        });
    }

    private void initComponents() {
        JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JTextField Field = new JTextField();
        //add filter to document
        ((AbstractDocument) Field.getDocument()).setDocumentFilter(new MyDocumentFilter());
        frame.add(Field);
        frame.pack();
        frame.setVisible(true);
    }
}

class MyDocumentFilter extends DocumentFilter {
    int z=0;
    @Override
    public void replace(FilterBypass fb, int i, int i1, String string, AttributeSet as) throws BadLocationException {
        for (int n = string.length(); n > 0; n--) {//an inserted string may be more than a single character i.e a copy and paste of 'aaa123d', also we iterate from the back as super.XX implementation will put last insterted string first and so on thus 'aa123d' would be 'daa', but because we iterate from the back its 'aad' like we want
            char c = string.charAt(n - 1);//get a single character of the string
            System.out.println(c);
            if(z==0){//for first character
                  if (Character.isAlphabetic(c)) {//if its an alphabetic character or white space
                      super.replace(fb, i, i1, String.valueOf(c), as);//allow update to take place for the given character
                      z++;
                  } else {//it was not an alphabetic character or white space
                      System.out.println("Not allowed");
                  }
            }
            else if(z!=0){
              if (Character.isAlphabetic(c) || c == ' ' || Character.isDigit(c)) {//if its an alphabetic character or white space
                  super.replace(fb, i, i1, String.valueOf(c), as);//allow update to take place for the given character
                  z++;
              } else {//it was not an alphabetic character or white space
                  System.out.println("Not allowed");
              }
            }

        }
    }

    @Override
    public void remove(FilterBypass fb, int i, int i1) throws BadLocationException {
        super.remove(fb, i, i1);
    }

    @Override
    public void insertString(FilterBypass fb, int i, String string, AttributeSet as) throws BadLocationException {
        super.insertString(fb, i, string, as);

    }
}

Answer 1

我不确定这是否是您要实现的目标，但如何将replace方法更改为

@Override
public void replace(FilterBypass fb, int i, int i1, String string, AttributeSet as) throws BadLocationException {
    //we want standard behavior if we are not placing space at start of JTextField
    //or if we are placing text at start of JTextField but first character is not whitespace
    if ( i!=0 || ( i==0 && !Character.isWhitespace(string.charAt(0)) ) ){
        super.replace(fb, i, i1, string, as);
    }else{
        System.out.println("no spaces allowed");
    }
}

Answer 2

尝试查看formattedtextfield java DOC。除了限制空格外，您还可以做很多事情。

MaskFormatter format = new MaskFormatter("A*********************");
JFormattedTextField fTxtFeild = new JFormattedTextField(format);

?中的第一个MaskFormatter指定任何任何字符或数字（Character.isLetter或Character.isDigit），*指定任何内容

限制jtextfield不接受空格作为第一个字符

2 个答案: