java - 如何验证 swt 文本小部件是十进制值

Question

在 swt 中，文本小部件允许任何字符串。
但是在其中输入 Decimal 值的最合适的 SWT 小部件是什么？

我找到了两个答案:

首先，实现VerifyKeyListener 和VerifyListener，使用法式十进制表示法，但实现简单易行:

package test.actions;

import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.eclipse.swt.custom.VerifyKeyListener;
import org.eclipse.swt.events.VerifyEvent;
import org.eclipse.swt.events.VerifyListener;
import org.eclipse.swt.widgets.Text;

public final class AmountVerifyKeyListener implements VerifyListener, VerifyKeyListener             {

    private static final String REGEX = "^[-+]?[0-9]*[,]?[0-9]{0,2}+$"; 

    private static final Pattern pattern = Pattern.compile(REGEX);  

    public void verifyText(VerifyEvent verifyevent) {
        verify(verifyevent);
    }

    public void verifyKey(VerifyEvent verifyevent) {
        verify(verifyevent);
    }

    private void verify (VerifyEvent e) {
        String string = e.text;
        char[] chars = new char[string.length()];
        string.getChars(0, chars.length, chars, 0);

        Text text = (Text)e.getSource();

        if ( ( ",".equals(string) || ".".equals(string) ) && text.getText().indexOf(',') >= 0 ) {
            e.doit = false;
            return;
        } 

        for (int i = 0; i < chars.length; i++) {
            if (!(('0' <= chars[i] && chars[i] <= '9') || chars[i] == '.' ||  chars[i] == ',' || chars[i] == '-')) {
                e.doit = false;
                return;
            } 


            if ( chars[i] == '.' ) {
                chars[i] = ',';
            }
        }

        e.text = new String(chars);

        final String oldS = text.getText();
        String newS = oldS.substring(0, e.start) + e.text + oldS.substring(e.end);
        Matcher matcher = pattern.matcher(newS);
        if ( !matcher.matches() ) {
            e.doit = false;
            return;
        }

    }
}

以及与 verifyKeyListener 关联的主类:

package test.actions;

import org.eclipse.swt.SWT;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.Text;

public class TestMain {

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setLayout(new GridLayout(2, false));

        final Text text = new Text(shell, SWT.NONE);

        text.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
        text.addVerifyListener(new AmountVerifyKeyListener() ) ;

        shell.pack();
        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) display.sleep();
        }
        display.dispose();
    }

}

使用来自星云项目的 FormattedText:http://eclipse.org/nebula/

有人看到另一种解决方案吗？

Answer 1

一种更简洁更简单的方法是使用 Double.parse String() 并捕获 NumberFormatException 以确定其中的文本是否可以转换为 double 值。