How to get label.getWidth() in javafx

问题:

always when i try to get the width of an Array in Java it just returns 0 and i dont know why. Can somebody explain to me how it is done right?

                Label label = new Label();
                label.setFont(Font.font(label.getFont().getFamily(), 8));
                label.setText(""
                        + a[i][j].getList().getFirst().getLength()
                        + " mal "
                        + intToColor(a[i][j].getList().getFirst()
                                .getColor()));
                label.relocate((x1 + x2) / 2 - label.getWidth() / 2, (y1 + y2) / 2);
                label.idProperty().set("trackName");
                label.setTextFill(Color.web("GREEN"));
                field.getChildren().addAll(path, label);
                System.out.println(label.getLayoutBounds().getWidth());
                System.out.println(label.getWidth());//... also i tested a lot of different getters but i couldn't get the label width (same problem with height)

Hope you got an idea what i have to do.

@tomsontom

did this:

                label.prefWidth(-1);
                label.prefHeight(-1);
                label.impl_processCSS(true);
//                  label.resizeRelocate(x, y, width, height);
                System.out.println(label.getWidth());

but it didnt worked - can you explain me more precisely what i need to do?

回答1:

To get the width you need to call prefWidth(-1) and prefHeight(-1) the layout bounds are only set once the control is layouted through resizeRelocate

To get the correct width before the stage is shown you also need to call impl_processCSS(true) which is an NONE public API but there's nothing better at the moment IIRC

 HBox h = new HBox();
 Label l = new Label("Hello");
 h.getChildren().add(l);
 Scene s = new Scene(h);
 l.impl_processCSS(true);
 System.err.println(l.prefWidth(-1)+"/"+l.prefHeight(-1));

回答2:

Another approach is to calculate the string width of the label's textProperty using Fontloader.computeStringWidth(text, font) which would output the pixel width of the label's textProperty, and is considerably similar to getting the label's width when the label is layouted at the later part.

For an instance:

    FontLoader fontLoader = Toolkit.getToolkit().getFontLoader();
    Label label = new Label("My name is Warren. I love Java.");
    label.setFont(Font.font("Consolas", FontWeight.THIN, FontPosture.REGULAR, 16));
    System.out.println("The label's width is: " + fontLoader.computeStringWidth(label.getText(), label.getFont()));

The output is:

The label's width is: 272.70312

To test:

    FontLoader fontLoader = Toolkit.getToolkit().getFontLoader();
    Label label = new Label("My name is Warren. I love Java.");
    label.setFont(Font.font("Consolas", FontWeight.THIN, FontPosture.REGULAR, 16));
    System.out.println("The label's textProperty string width is: " + fontLoader.computeStringWidth(label.getText(), label.getFont()));
    System.out.println("Label's width before layouted: " + label.getWidth());
    primaryStage.setScene(new Scene(new StackPane(label), 300, 250));
    primaryStage.show();
    System.out.println("Label's width after layouted: " + label.getWidth());

Here's the output

The label's textProperty string width is: 272.70312
Label's width before layouted: 0.0
Label's width after layouted: 273.0

Comparably, they are the same. Hope this helps.

回答3:

I don't think the width will be calculated until the Label is shown: add it to a Parent that is visible and you should get a non-zero result.

回答4:

You can try the following:

func foo()
{
    label.layout();

    Platform.runLater(()->
    {
        System.out.println(label.getWidth());
    });
}