JFormattedTextField输入第一个数字时插入符号位置错误

Question

我修改了NumberFormatter，使其具有货币实例(带有前缀)。当我写第一个号码时，这个应用程序已经为号码添加了前缀JFormattedTextField时空但是当我这样做的时候，插入符号的位置在第一个数字之前改变了，像这样输入图片描述

如何通过仅修改方法formato()-返回NumberFormatter-JFormattedTextField的构造函数来修复此问题?

textFieldMonto = new javax.swing.JFormattedTextField(formato());

方法:

private NumberFormatter formato() {
DecimalFormat myFormatter = new DecimalFormat("'Gs. '###,##0;'Gs. '###,##0");
NumberFormatter numberFormatter = new NumberFormatter(myFormatter) {
// this change caret to the end in every focus gained
@Override
public void install(JFormattedTextField pField) {
super.install(pField);
pField.setCaretPosition(pField.getDocument().getLength());
}
// allow empty text on JFormattedTextField and dont allow negative numbers
@Override
public String valueToString(Object value) throws ParseException {
String result = super.valueToString(value);
if(super.valueToString(value).startsWith("-"))
result = result.replaceFirst("-", "");  // this block every negative number
if(value==null)
return "";
return result;
}
// allow empty text on JFormattedTextField and dont allow negative numbers
@Override
public Object stringToValue(String text) throws ParseException {
if (text.length() == 0 || text.equals("Gs. ")) // if is empty or only have the prefix, return null
return null;
text.replaceFirst("-", ""); // this block every negative number
if(!text.startsWith("Gs. "))   //if is empty, add the prefix "Gs. " to the number
text = "Gs. " + text;
return super.stringToValue(text);
}
};
numberFormatter.setAllowsInvalid(false); //this is the key!!
numberFormatter.setMaximum(new BigDecimal("999999999999"));// maximum number to put
numberFormatter.setCommitsOnValidEdit(true);// commit value on each keystroke instead of focus lost
return numberFormatter;
}

Answer 1

我不认为这个评论，在你的问题中的代码，是真的:

// this change caret to the end in every focus gained

方法install不是每次JFormattedTextField获得焦点时调用。根据我的测试，它只在创建JFormattedTextField对象时被调用。

根据javadoc:

子类通常只需要在它们希望在JFormattedTextField上安装额外的侦听器时重写它。

因此，我建议在install方法中为JFormattedTextField的文档添加DocumentListener。

请注意，还有其他DocumentListener是由Swing基础设施设置的，并且由于在存在多个DocumentListener时无法保证执行顺序，因此在下面的代码中，实现使用invokeLater来确保我添加的侦听器是最后运行的。

这是我重写你的formato方法。
唯一改变的是方法install。

private NumberFormatter formato() {
DecimalFormat myFormatter = new DecimalFormat("'Gs. '###,##0;'Gs. '###,##0");
NumberFormatter numberFormatter = new NumberFormatter(myFormatter) {
// this change caret to the end in every focus gained
@Override
public void install(JFormattedTextField pField) {
super.install(pField);
pField.getDocument().addDocumentListener(new DocumentListener() {
@Override
public void insertUpdate(DocumentEvent e) {
EventQueue.invokeLater(() -> pField.setCaretPosition(pField.getDocument().getLength()));
}
@Override
public void removeUpdate(DocumentEvent e) {
EventQueue.invokeLater(() -> pField.setCaretPosition(pField.getDocument().getLength()));
}
@Override
public void changedUpdate(DocumentEvent e) {
// Do nothing.
}
});
}
// allow empty text on JFormattedTextField and don't allow negative numbers
@Override
public String valueToString(Object value) throws ParseException {
String result = super.valueToString(value);
if(super.valueToString(value).startsWith("-"))
result = result.replaceFirst("-", "");  // this block every negative number
if(value==null)
return "";
return result;
}
// allow empty text on JFormattedTextField and don't allow negative numbers
@Override
public Object stringToValue(String text) throws ParseException {
if (text.length() == 0 || text.equals("Gs. ")) // if is empty or only have the prefix, return null
return null;
text.replaceFirst("-", ""); // this block every negative number
if(!text.startsWith("Gs. "))   //if is empty, add the prefix "Gs. " to the number
text = "Gs. " + text;
return super.stringToValue(text);
}
};
numberFormatter.setAllowsInvalid(false); //this is the key!!
numberFormatter.setMaximum(new BigDecimal("999999999999"));// maximum number to put
numberFormatter.setCommitsOnValidEdit(true);// commit value on each keystroke instead of focus lost
return numberFormatter;
}