How do I center JavaFX controls

Question

More specifically, why are my JavaFX controls not being centered? Here are two screenshots, the first just after starting (I moved the window into a more visible spot but have n

Answer 1

Resize Issue

Make sure you are adding a size to your JFrame

frame.setSize(500, 300);

Center Issue

I am not sure whether you are taking about centering your frame or the JavaFX controls in the GridPane, so I am adding answers for both of them

Frame Screen Centering

Dimension dim = Toolkit.getDefaultToolkit().getScreenSize();
frame.setLocation(dim.width/2-frame.getSize().width/2, 
                                        dim.height/2-frame.getSize().height/2);

GridPane Child Centering

You need to add

GridPane.setHalignment(child, HPos.CENTER);

to your code, remove the rest unnecessary code

I edited your code :

{
    Label statusLabel = new Label("Checking for Updates...");
    //statusLabel.setAlignment(Pos.CENTER);
    //statusLabel.setTextAlignment(TextAlignment.CENTER);
    rootGrid.add(statusLabel, 0, 0);
    GridPane.setHalignment(statusLabel, HPos.CENTER);
}
{
    ProgressBar progressBar = new ProgressBar();
    progressBar.setProgress(-1);
    progressBar.setPrefWidth(400); // 1/5 the width of the screen
    rootGrid.add(progressBar, 0, 1);
}
{
    Button downloadButton = new Button("Get it!");
    //downloadButton.setAlignment(Pos.CENTER);
    rootGrid.add(downloadButton, 0, 2);
    GridPane.setHalignment(downloadButton, HPos.CENTER);
}

and the result is