Javafx - 线程“main”java.lang.ExceptionInInitializerError中的异常

Question

我正在尝试使用几个textFields，一个提交和清除按钮重新创建一个简单的JFrame，就像下面教程中的图8-2一样：

http://docs.oracle.com/javafx/2/ui_controls/text-field.htm

但我一直收到错误：

Exception in thread "main" java.lang.ExceptionInInitializerError
Caused by: java.lang.IllegalStateException: Toolkit not initialized

在这行代码中：

final TextField totTime = new TextField();

我对使用Javafx有些新意，为什么我会给出这个错误？谢谢！

public static void main(String[] args) throws IOException 
{

    //Creating GridPane container
    GridPane grid = new GridPane();
    grid.setPadding(new Insets(10, 10, 10, 10));
    grid.setVgap(5);
    grid.setHgap(5);

    //Defining Total Time
    final TextField totTime = new TextField();
    totTime.setPromptText("Enter Simulation Duration (Double)");
    totTime.setPrefColumnCount(5);
    totTime.getText();
    GridPane.setConstraints(totTime, 0, 0);
    grid.getChildren().add(totTime);

    //Defining the Submit button
    Button submit = new Button("Submit");
    GridPane.setConstraints(submit, 1, 0);
    grid.getChildren().add(submit);

    //Defining the Clear button
    Button clear = new Button("Clear");
    GridPane.setConstraints(clear, 1, 1);
    grid.getChildren().add(clear);
}