JTextField只接受有效的无符号短裤？(使用KeyAdapter)

Question

下面是KeyAdapter我试图只接受小于65535的值.看起来好像它实际应该在它后面的一个击键.例如,如果我输入"55",System.out.println将产生"5",执行"3298"将产生"329"等.

// Allows for unsigned short values only
KeyAdapter unsignedShortAdapter = new KeyAdapter() {

    public void keyTyped(KeyEvent e) {
        char c = e.getKeyChar();
        int tempInt = 0;
        JTextField temp = null;

        if (!((Character.isDigit(c) || (c == KeyEvent.VK_BACK_SPACE) || (c == KeyEvent.VK_DELETE)))) {
            getToolkit().beep();
            e.consume();
        }
        try {
            temp = (JTextField) e.getSource();
            System.out.println(temp.getText());
            tempInt = (Integer.parseInt(temp.getText().toString()));
        } catch (NumberFormatException e1) {

        } finally {
            if (tempInt > (Short.MAX_VALUE * 2)) {
                 getToolkit().beep();
                 e.consume();
                temp.setText(temp.getText().substring(0, temp.getText().length() - 1));

                invalidate();
            }

        }
    }

};

Answer 1

所以,KeyListener你找到的不是一个不可靠的东西,而且会造成许多令人讨厌的副作用(以及可能的文件突变异常:P),我们应该使用a DocumentFilter,因为它是为它设计的

public class ShortFilter extends DocumentFilter {

    protected boolean valid(String text) {


        boolean valid = true;
        for (char check : text.toCharArray()) {

            if (!Character.isDigit(check)) {

                valid = false;
                break;

            }

        }

        if (valid) {

            int iValue = Integer.parseInt(text);

            valid = iValue <= (Short.MAX_VALUE * 2);

        }

        return valid;

    }

    @Override
    public void insertString(FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {

        StringBuilder sb = new StringBuilder(fb.getDocument().getText(0, fb.getDocument().getLength()));
        sb.insert(offset, text);

        if (valid(sb.toString())) {

            super.insertString(fb, offset, text, attr);

        }

    }

    @Override
    public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs) throws BadLocationException {

        if (length > 0) {

            StringBuilder sb = new StringBuilder(fb.getDocument().getText(0, fb.getDocument().getLength()));

            sb.delete(offset, length);
            sb.insert(offset, text);

            if (valid(sb.toString())) {

                super.replace(fb, offset, length, text, attrs);

            }

        } else {

            insertString(fb, offset, text, attrs);

        }

    }
}

您需要将其应用于该字段的文档

((AbstractDocument) field.getDocument()).setDocumentFilter(new ShortFilter());

我退房了

• http://www.jroller.com/dpmihai/entry/documentfilter
• http://docs.oracle.com/javase/7/docs/api/javax/swing/text/DocumentFilter.html

有关更多信息

更新为十进制包含

基本上,如果要允许包含小数,则需要允许valid方法中的字符.

您还需要检查当前文档的内容

StringBuilder sb = new StringBuilder(fb.getDocument().getText(0, fb.getDocument().getLength()));

// Update the StringBuilder as per noraml
// Check valid as per normal

if (text.contains(".") && sb.contains(".")) {
  // already have decimal place
} else {
  // Business as usual...
}