Swing —— 限制JTextArea唯其如此输入浮点数

下面是示例代码： 

[复制源代码]

class JTextFieldFilterextends PlainDocument {

public static final StringFLOAT = "0123456789.";

protected String acceptedChars = null;

protected boolean negativeAccepted =false;

public JTextFieldFilter() {

this(FLOAT);

}

public JTextFieldFilter(String acceptedChars) {

this.acceptedChars = acceptedChars;

}

/**

 *设置是否接受负号

 *

 * @param negativeAccepted

 *           是否接受负号

 */

public void setNegativeAccepted(boolean negativeAccepted) {

if (acceptedChars.equals(FLOAT)) {

this.negativeAccepted = negativeAccepted;

acceptedChars += "-";

}

}

public void insertString(int offset, String str, AttributeSet attr)

throws BadLocationException {

//判断输入的是否为允许的字符

for (int i = 0; i < str.length(); i++) {

if (!acceptedChars.contains(str)) {

return;

}

}

//判断当前输入的是否为".",如果有了再判断前面有没有输入过

if (acceptedChars.equals(FLOAT)

|| (acceptedChars.equals(FLOAT +"-") && negativeAccepted)) {

if (str.contains(".")) {

if (getText(0, getLength()).contains(".")) {

return;

}

}

}

//判断如果支持负数,那么负号(-)必须在第一位

if (negativeAccepted) {

if (str.indexOf("-") != 0 || offset != 0) {

return;

}

}

super.insertString(offset, str, attr);

}

}

publicclass Main extends JFrame {

public static void main(String[] argv)throws Exception {

new Main();

}

public Main() {

setLayout(new FlowLayout());

JLabel lb = new JLabel("only float");

JTextField tf = new JTextField(10);

getContentPane().add(lb);

getContentPane().add(tf);

tf.setDocument(new JTextFieldFilter(JTextFieldFilter.FLOAT));

setSize(300, 300);

setVisible(true);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

}