JavaFX静态与非静态 [英] JavaFX Static vs non Static

问题描述

美好的一天，

为什么JavaFX有问题，如果我在一个方法之外创建一个静态标签，但是对于像a这样的形状不会有同样的问题球体或矩形。

Why does JavaFX have a problem, if i create a static Label outside a method, but doesen't have the same problem with shapes like a sphere or a rectangle.

以下工作正常：

static Rectangle upperBorder = new Rectangle(0, 0, 10, 10);

但这会产生异常：

static Label myScore = new Label("Test");

我必须按以下方式创建标签：

I have to create the Label the following way:

Label myScore = new Label("Test");

这是没有static关键字。

This is without the "static" keyword.

这是错误：

Exception in thread "main" java.lang.ExceptionInInitializerError
at pong.Main.<clinit>(Main.java:24)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:264)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:122)
Caused by: java.lang.IllegalStateException: Toolkit not initialized
at com.sun.javafx.application.PlatformImpl.runLater(PlatformImpl.java:273)
at com.sun.javafx.application.PlatformImpl.runLater(PlatformImpl.java:268)
at com.sun.javafx.application.PlatformImpl.setPlatformUserAgentStylesheet(PlatformImpl.java:550)
at com.sun.javafx.application.PlatformImpl.setDefaultPlatformUserAgentStylesheet(PlatformImpl.java:512)
at javafx.scene.control.Control.<clinit>(Control.java:87)
... 4 more

推荐答案

错误很可能不是由 static 关键字引起的。

The error is most likely not caused by the static keyword.

考虑这个简单的测试程序：

Consider this simple test program:

public class Test {

   static Rectangle a   = new Rectangle(0, 0, 10, 10);
   static Label     b   = new Label("b");

   public static void main(String[] args) {
   }
}

启动时抛出异常：

Exception in thread "main" java.lang.ExceptionInInitializerError
   at Test.<clinit>(Test.java:7)
Caused by: java.lang.IllegalStateException: Toolkit not initialized
   at com.sun.javafx.application.PlatformImpl.runLater(PlatformImpl.java:273)
   at com.sun.javafx.application.PlatformImpl.runLater(PlatformImpl.java:268)
   at com.sun.javafx.application.PlatformImpl.setPlatformUserAgentStylesheet(PlatformImpl.java:550)
   at com.sun.javafx.application.PlatformImpl.setDefaultPlatformUserAgentStylesheet(PlatformImpl.java:512)
   at javafx.scene.control.Control.<clinit>(Control.java:87)
   ... 1 more

这暗示JavaFX应用程序平台未启动。在此示例中删除 static 关键字时，错误似乎消失，但这是因为标签 b 不是在代码中使用。

This hints at the JavaFX Application Platform not being started. The error seems to disappear when the static keyword is removed in this example, but that is because the label b is not used in the code.

启动与JavaFX应用程序相同的类可确保在第一个控件之前初始化Platform 已创建：

Launching the same class as a JavaFX Application ensures that the Platform is initialized before the first Control is created:

public class Test extends Application {

   static Rectangle a   = new Rectangle(0, 0, 10, 10);
   static Label     b   = new Label("b");

   public static void main(String[] args) {
      launch(args);
   }

   @Override
   public void start(Stage primaryStage) throws Exception {
      // TODO Auto-generated method stub
   }
}

Rectangle 和<$之间的区别您的代码中的c $ c>标签是标签是 Control 和矩形不是。没有正在运行的JavaFX平台，无法实例化标签。

The difference between Rectangle and Label in your code is that Label is a Control and Rectangle is not. Label can not be instantiated without a running JavaFX Platform.

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