JavaFX Alerts and their size

Another solution is subclassing the Alert and applying desired style there, for example:

class SubAlert extends Alert {
    {
        setHeaderText("");
        getDialogPane().getStylesheets().add("some_stylesheet");
        getDialogPane().getStyleClass().add("style_class");
        getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
    }

    SubAlert(AlertType alertType) {
        super(alertType);
    }

    SubAlert(AlertType type, String title, String content) {
        super(type);
        setTitle(title);
        setContentText(content);
    }
}

This way you don't have to repeat actions for every Alert you create.

I have made the following workaround:

Alert alert = new Alert(AlertType.INFORMATION, "Content here", ButtonType.OK);
alert.getDialogPane().setMinHeight(Region.USE_PREF_SIZE);
alert.show();

So the window will resize automatically according to the content.

Here is the better workaround without magic numbers, resizing etc.:

Alert alert = new Alert(AlertType.ERROR, "content text");
alert.getDialogPane().getChildren().stream().filter(node -> node instanceof Label).forEach(node -> ((Label)node).setMinHeight(Region.USE_PREF_SIZE));

This solution works under Windows, Linux and Mac.

I have made the following workaround sometime ago:

Alert dialog = new Alert(Alert.AlertType.ERROR);
dialog.setHeaderText("Connection Failed");
dialog.setContentText(this.getException().getMessage());

//FIXME: Remove after release 8u40
dialog.setResizable(true);
dialog.getDialogPane().setPrefSize(480, 320);

dialog.showAndWait();

As you can see I just set resizable flag and set preferred size.

But this is strange because this bug should be fixed in 8u40. Are you using latest build of 8u40?

UPDATE:

Not fixed in 8u40. Should be fixed later.