JavaFX 8与数字格式绑定

Question

谁能告诉我一个绑定的例子。bindBidirectional，将文本字段绑定到Double值，并且将文本字段格式化为小数点后零位。我有这样的绑定:

Bindings.bindBidirectional(xProperty, sp.layoutXProperty(), converter);

其中xProperty为StringProperty, sp.layoutXProperty为DoubleProperty。

我尝试了许多不同的转换器，最后决定:

NumberFormat nf = NumberFormat.getInstance();    
StringConverter<Number> converter = new NumberStringConverter(nf);

Then I try:

nf.setParseIntegerOnly(true);

但无济于事。这只是为达到这个结果而进行的众多尝试中的一次。这可能很直接，但是关于将不同属性与格式绑定的信息似乎很少，或者我错过了明显的信息吗?

Answer 1

看一下这段代码，看看它是否解决了你的问题:

public class BindingTest {
    static Property<String> sp;
    static Property<Double> dp;
    public static void main(String[] args) {
        sp = new SimpleStringProperty();
        dp = new SimpleObjectProperty<>();
        StringConverter<Double> sc = new StringConverter<Double>() {
            @Override
            public String toString(Double object) {
                if (object != null)
                    return Integer.toString((int) Math.round(object.doubleValue()));
                else
                    return null;
            }
            @Override
            public Double fromString(String string) {
                Double d = Double.parseDouble(string);
                sp.setValue(Integer.toString((int) Math.round(d)));
                return d;
            }
        };
        Bindings.bindBidirectional(sp, dp, sc);
        print();
        sp.setValue("3.14");
        print();
        dp.setValue(6.18);
        print();
    }
    public static void print() {
        System.out.println("String: " + sp.getValue() + "t" + "Double: " + dp.getValue());
    }
}

输出:

String: null    Double: null
String: 3   Double: 3.14
String: 6   Double: 6.18

Answer 2

可能有不同的方法将双精度值转换为整数，在转换时使用不同的四舍五入。这个答案与其他答案类似，它有一个额外的过滤器，只允许文本字段中的整数值:

@Override
public void start( Stage stage )
{
    TextField field = new TextField();
    DoubleProperty doubleProperty = new SimpleDoubleProperty();
    Label label = new Label();
    label.textProperty().bind( doubleProperty.asString() );
    DecimalFormat format = new DecimalFormat();
    format.setParseIntegerOnly( true );  // used while parsing the input text of textfield
    format.setMaximumFractionDigits( 0 );  // used while formatting the doubleProperty's bound value as output text of textfield
    format.setGroupingUsed( false );  // disable thousand grouping
    format.setRoundingMode( RoundingMode.UP );  // set rounding mode
    Bindings.bindBidirectional( field.textProperty(), doubleProperty, new StringConverter<Number>()
    {
        @Override
        public String toString( Number object )
        {
            return object == null ? "" : format.format( object );
        }

        @Override
        public Number fromString( String string )
        {
            return (string != null && !string.isEmpty()) ? Double.valueOf( string ) : null;
        }
    } );
    // apply filter to allow only integer values
    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;
        }
    } ) );
    Button b = new Button( "+1.6" );
    b.setOnAction( ( e ) ->
    {
        doubleProperty.set( doubleProperty.get() + 1.6 );
    } );
    Scene scene = new Scene( new VBox( 5 ) );
    stage.setWidth( 450 );
    stage.setHeight( 250 );
    (( VBox ) scene.getRoot()).getChildren().addAll( field, label, b );
    stage.setScene( scene );
    stage.show();
}