Java 8 U40 TextFormatter (JavaFX) 限制用户仅输入十进制数 [英] Java 8 U40 TextFormatter (JavaFX) to restrict user input only for decimal number

问题描述

我正在寻找一个示例，使用 Java8 u40 的新类 TextFormatter 将用户输入限制为仅数字和小数点.http://download.java.net/jdk9/jfxdocs/javafx/scene/control/TextFormatter.Change.html

I am looking for an example to restrict user input to only digits and decimal points using the new class TextFormatter of Java8 u40. http://download.java.net/jdk9/jfxdocs/javafx/scene/control/TextFormatter.Change.html

推荐答案

请看这个例子:

DecimalFormat format = new DecimalFormat( "#.0" );

TextField field = new TextField();
field.setTextFormatter( new TextFormatter<>(c ->
{
    if ( c.getControlNewText().isEmpty() )
    {
        return c;
    }

    ParsePosition parsePosition = new ParsePosition( 0 );
    Object object = format.parse( c.getControlNewText(), parsePosition );

    if ( object == null || parsePosition.getIndex() < c.getControlNewText().length() )
    {
        return null;
    }
    else
    {
        return c;
    }
}));

• 这里我使用了 TextFormatter(UnaryOperator filter) 构造函数，只将过滤器作为参数.

  • Here I used the TextFormatter(UnaryOperator filter) constructor which takes a filter only as a parameter.

    要了解 if 语句，请参阅 DecimalFormat parse(String text, ParsePosition pos).

    To understand the if-statement refer to DecimalFormat parse(String text, ParsePosition pos).

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