JTextField 限制字符数量输入并仅接受数字

问题描述

这是我关于如何限制字符输入长度的代码

here's the code that i have on how to limit the character input length

class JTextFieldLimit extends PlainDocument {
  private int limit;
  // optional uppercase conversion
  private boolean toUppercase = false;

  JTextFieldLimit(int limit) {
   super();
   this.limit = limit;
   }

  JTextFieldLimit(int limit, boolean upper) {
   super();
   this.limit = limit;
   toUppercase = upper;
   }

    @Override
  public void insertString
    (int offset, String  str, AttributeSet attr)
      throws BadLocationException {
   if (str == null) return;

   if ((getLength() + str.length()) <= limit) {
     if (toUppercase) str = str.toUpperCase();
     super.insertString(offset, str, attr);
     }
   }
}

可以通过txtSample.setDocument(new JTextFieldLimit(30));

这是我只接受数字的内容(尽管我不需要，但它接受十进制数)

and here's what i have on accepting numeric numbers only(it accepts decimal though w/c i dont need)

class NumericDocument extends PlainDocument {

     protected int decimalPrecision = 0;
     protected boolean allowNegative = false;


     public NumericDocument(int decimalPrecision, boolean allowNegative) {
          super();
          this.decimalPrecision = decimalPrecision;
          this.allowNegative = allowNegative;
     }



    @Override
     public void insertString(int offset, String str, AttributeSet attr) throws BadLocationException {
          if (str != null){
               if (StringFormat.isNumeric(str) == false && str.equals(".") == false && str.equals("-") == false){ //First, is it a valid character?
                    Toolkit.getDefaultToolkit().beep();
                    return;
               }
               else if (str.equals(".") == true && super.getText(0, super.getLength()).contains(".") == true){ //Next, can we place a decimal here?
                    Toolkit.getDefaultToolkit().beep();
                    return;
               }
               else if (StringFormat.isNumeric(str) == true && super.getText(0, super.getLength()).indexOf(",") != -1 && offset>super.getText(0, super.getLength()).indexOf(",") && super.getLength()-super.getText(0, super.getLength()).indexOf(".")>decimalPrecision && decimalPrecision > 0){ //Next, do we get past the decimal precision limit?
                    Toolkit.getDefaultToolkit().beep();
                    return;
               }
               else if (str.equals("-") == true && (offset != 0 || allowNegative == false)){ //Next, can we put a negative sign?
                    Toolkit.getDefaultToolkit().beep();
                    return;
               }


               super.insertString(offset, str, attr);
          }
          return;
     }
public static class StringFormat
{
    public StringFormat()
    {
    }
    public static boolean isNumeric(String str)
    {
        try
        {
            int x = Integer.parseInt(str);
            System.out.println(x); return true;
        } catch(NumberFormatException nFE)
        {
            System.out.println("Not an Integer"); return false;
        }
    }
}

}

以及如何使用此代码:txtSample.setDocument(new NumericDocument(0,false));

现在的问题是txtSample 只能setDocument 一次.如何限制 jtextfield 长度并同时仅接受数字?或者有没有更简单的方法来做到这一点?谢谢.:D

now the problem is the txtSample can only setDocument once. How do i limit a jtextfield length and accept numbers only at the same time? Or is there any simpler way to do this? Thanks. :D

推荐答案

您走在正确的轨道上，除非您想使用 DocumentFilter 而不是实现您自己的文档.

You're on the right track, except you will want to use a DocumentFilter instead of implementing your own document.

MDP 的博客有很多很好的例子(包括限制长度和字符类型).

MDP's Weblog has a number of excellent examples (including limiting the length and character type).

现在回答您的问题，您可以创建级联过滤器，您可以在其中将一系列过滤器链接在一起.

Now to the your question, you could create cascading filter, where you could chain a series of filters together.

这将允许您依次调用每个过滤器.

This would allow you to call each filter in turn.

public class ChainableFilter extends DocumentFilter {

    private List<DocumentFilter> filters;
    private AttributeSet attr;

    public ChainableFilter() {
        filters = new ArrayList<DocumentFilter>(25);
    }

    public void addFilter(DocumentFilter filter) {
        filters.add(filter);
    }

    public void removeFilter(DocumentFilter filter) {
        filters.remove(filter);
    }

    public void insertString(DocumentFilter.FilterBypass fb, int offset, String string, AttributeSet attr) throws BadLocationException {
        for (DocumentFilter filter : filters) {
            filter.insertString(fb, offset, string, attr);
        }
    }        

    public void remove(DocumentFilter.FilterBypass fb, int offset, int length) throws BadLocationException {
        for (DocumentFilter filter : filters) {
            filter.remove(fb, offset, length);
        }
    }

    public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
        for (DocumentFilter filter : filters) {
            filter.replace(fb, offset, length, text, attrs);
        }
    }

}

现在，如果过滤器真的可以告诉链它是否改变了文档，那就太好了，但我会把它留给你

Now it would be nice if filter could actually tell the chain if it altered the document at all, but I'll leave that up to you

更新

您所做的与DocumentFilters 的工作方式之间的基本概念几乎相同.好处是，您不会将自己限制在 PlainDocument，理论上，您可以将其应用于 JTextPane 或 JEditorPane.

The basic concept between what you've done and how DocumentFilters work is pretty much the same. The benefit is, you're not limiting your self to a PlainDocument, you could, in theory, apply it to a JTextPane or JEditorPane.

过滤器链的基本思想很简单.

The basic idea of the filter chain is simple.

ChainableFilter chainableFilter = new ChainableFilter();
chainableFilter.addFilter(new RestrictedLengthFilter()); // User supplied filter 
chainableFilter.addFilter(new NumericFilter()); // User supplied filter 

((AbstractDocument)textField.getDocument()).setDocumentFilter(chainableFilter);

至于实际的过滤器，我会查看我之前发布的链接.不过你的想法是正确的

As for the actual filters, I'd check out the link I posted earlier. You're on the right track with your ideas though

更新

SizeFilter sizeFilter = new SizeFilter(12);
NumberFilter numFilter = new NumberFilter();
ChainableFilter chainFilter = new ChainableFilter();
chainFilter.addFilter(sizeFilter);
chainFilter.addFilter(numFilter);

JTextField field = new JTextField();
((AbstractDocument) field.getDocument()).setDocumentFilter(chainFilter);



    public class NumberFilter extends DocumentFilter {

        private int decimalPrecision = 2;
        private boolean allowNegative = false;

        public NumberFilter() {
        }

        public NumberFilter(int decimals, boolean negatives) {
            decimalPrecision = decimals;
            allowNegative = negatives;
        }

        protected boolean accept(FilterBypass fb, int offset, String str) throws BadLocationException {
            boolean accept = true;    
            int length = fb.getDocument().getLength();
            String currentText = fb.getDocument().getText(0, length);

            if (str != null) {
                if (!isNumeric(str) && !str.equals(".") && !str.equals("-")) { //First, is it a valid character?
                    Toolkit.getDefaultToolkit().beep();
                    accept = false;
                } else if (str.equals(".") && currentText.contains(".")) { //Next, can we place a decimal here?
                    Toolkit.getDefaultToolkit().beep();
                    accept = false;
                } else if (isNumeric(str)
                                && currentText.indexOf(",") != -1
                                && offset > currentText.indexOf(",")
                                && length - currentText.indexOf(".") > decimalPrecision
                                && decimalPrecision > 0) { //Next, do we get past the decimal precision limit?
                    Toolkit.getDefaultToolkit().beep();
                    accept = false;
                } else if (str.equals("-") && (offset != 0 || !allowNegative)) { //Next, can we put a negative sign?
                    Toolkit.getDefaultToolkit().beep();
                    accept = false;
                }
            }
            return accept;
        }

        @Override
        public void insertString(FilterBypass fb, int offset, String str, AttributeSet as) throws BadLocationException {
            if (accept(fb, offset, str)) {
                super.insertString(fb, offset, str, as);
            }
        }

        @Override
        public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {
            if (accept(fb, offset, text)) {
                super.replace(fb, offset, length, text, attrs);
            }
        }

        public boolean isNumeric(String str) {
            try {
                int x = Integer.parseInt(str);
                System.out.println(x);
                return true;
            } catch (NumberFormatException nFE) {
                System.out.println("Not an Integer");
                return false;
            }
        }
    }

    public class SizeFilter extends DocumentFilter {

        private int maxCharacters;

        public SizeFilter(int maxChars) {
            maxCharacters = maxChars;
        }

        public void insertString(FilterBypass fb, int offs, String str, AttributeSet a)
                        throws BadLocationException {

            if ((fb.getDocument().getLength() + str.length()) <= maxCharacters) {
                super.insertString(fb, offs, str, a);
            } else {
                Toolkit.getDefaultToolkit().beep();
            }
        }

        public void replace(FilterBypass fb, int offs, int length, String str, AttributeSet a)
                        throws BadLocationException {

            if ((fb.getDocument().getLength() + str.length()
                     - length) <= maxCharacters) {
                super.replace(fb, offs, length, str, a);
            } else {
                Toolkit.getDefaultToolkit().beep();
            }
        }
    }

再说一次，我知道它可以编译，但我还没有测试过它(特别是数字过滤器)，但这将是一个很好的调试练习；)

Again, I know it compiles, but I've not tested it (the numeric filter in particular), but that would be a good exercise in debugging ;)

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