匿名用户
1级
2016-11-07 回答
使用DocumentFilter
import java.awt.EventQueue;
import java.awt.GridBagLayout;
import java.awt.Toolkit;
import javax.print.attribute.AttributeSet;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.text.AbstractDocument;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
import javax.swing.text.DocumentFilter.FilterBypass;
public class FilterTest {
public static void main(String[] args) {
new FilterTest();
}
public FilterTest() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
JTextField field = new JTextField(10);
((AbstractDocument)field.getDocument()).setDocumentFilter(new SizeFilter(5));
JFrame frame = new JFrame("Testing");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new GridBagLayout());
frame.add(field);
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
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();
}
}
}
}
追问：
作为一个JAVA初学者，表示这串代码压力很大
(#ﾟДﾟ) 问个小问题，我是通过int转string length的方式来完成字符长度限制的，其中我加入try语句用来报错返回，但是编译通过了，但是catch语句没有被触发该怎么办，报错码是InputMismatchException