Swing/AWT/JavaFX 界面 Freezing/NullPointerException

Question

我有一个 class 扩展应用程序：

public class IO extends Application {
    private static JFrame frame = new JFrame("Shapes");;
    private final JPanel content = new JPanel();
    private final JPanel drawingArea = new JPanel();

我的main/start方法：

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

public void start(Stage primaryStage) throws Exception {
    SwingUtilities.invokeLater(new Runnable() {
        public void run() {
            new JFXPanel(); // initializes JavaFX environment
            createGUI();
        }
    });
}

我这样做是为了希望解决每个 this question 的 swing/JavaFX 组件之间的任何问题。但是，当我单击一个将 JPanel 或 JFXPanel 添加到另一个 JPanel 的按钮时，如果它是 JFXPanel，它将执行一次就好了，但此后我再次尝试生成 JFXPanel 时它会失败，给出“线程“AWT-EventQueue-0”java.lang.NullPointerException”中的异常（但实际上总共需要 3 次才能出现此错误 - 第二次它将冻结，如果没有，则什么都不做）。这是按钮的相关代码：

JButton go = new JButton("Go");
go.addActionListener(new ActionListener() {
    // irrelevant code
        System.out.println("Shape set parameters: " + selectedShape.setParameters(shapeParams));
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new JFXPanel(); // initializes JavaFX environment
                Component shapePanel = (Component) new PaintedShape(selectedShape).getPanel();
                drawingArea.add(shapePanel);
                // drawingArea.add(new JLabel("Test"));
                // drawingArea.repaint();
                shapePanel.repaint();
                shapePanel.validate();
                drawingArea.repaint();
                drawingArea.validate();
                frame.pack();
                frame.setSize(new Dimension((int) (frame.getSize().getWidth() + PaintedShape.size.getWidth()),
                        (int) (frame.getSize().getHeight() + PaintedShape.size.getHeight())));
                frame.setLocationRelativeTo(null);
            }
        });
    }
});
params.add(go);
content.validate();

我多次调用 validate()，因为它有时无法添加形状，其中一组调用最初修复了该错误。如果您解释哪个面板更适合我调用它，则可加分。如果您觉得需要其余代码，我创建了一个 github 存储库 here.

编辑：完整的堆栈跟踪 -

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at com.sun.javafx.tk.quantum.QuantumToolkit.isSupported(QuantumToolkit.java:1153)
    at com.sun.javafx.application.PlatformImpl.isSupportedImpl(PlatformImpl.java:809)
    at com.sun.javafx.application.PlatformImpl.isSupported(PlatformImpl.java:482)
    at javafx.application.Platform.isSupported(Platform.java:168)
    at javafx.scene.shape.Shape3D.<init>(Shape3D.java:74)
    at javafx.scene.shape.Cylinder.<init>(Cylinder.java:89)
    at shapes.PaintedShape.painted3DShapePanel(PaintedShape.java:96)
    at shapes.PaintedShape.<init>(PaintedShape.java:51)
    at shapes.IO.run(IO.java:215)
    at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:311)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access0(EventQueue.java:97)
    at java.awt.EventQueue.run(EventQueue.java:709)
    at java.awt.EventQueue.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:74)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:205)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

编辑：调试进一步让我发现无法在 PaintedShape.java 中实例化任何新的三维 javafx 形状（请参阅堆栈跟踪的第 6 行 - at javafx.scene.shape.Shape3D.<init>(Shape3D.java:74)），这可能是由于线程安全。我的一些修复包含在下面的答案中，但我没有提到，尽管我的代码被包装在 Runnable()s“稍后调用”中，但我将特定的 JFXPanel 生成代码冗余嵌套在与以下代码相同的可运行结构中出色地。这可能有所帮助，但我不确定如何。

Platform.runLater(() -> {
    try {
        SwingUtilities.invokeLater(() -> {
            drawingPanel.add(shapePanel);
            frame.pack();
        });

    } catch (Exception e) {
        e.printStackTrace();
    }

});

Answer 1

已修复。我相信错误可能是，在从 JPanel drawingArea 中删除所有元素后，它不会立即 validate()d，因此不支持向其添加元素。我还确保 JFXPanel 是这样输入的，而不是被转换为组件。我还确保每次通过 JPanel drawing 按下按钮时都会创建它添加到的 JPanel，以防它在之前的方法范围内由于某种原因很重要。参见：

go.addActionListener(new ActionListener() {
    @Override
    public void actionPerformed(ActionEvent e) {
    final JPanel drawing = new JPanel();
        // irrelevant
        SwingUtilities.invokeLater(new Runnable() {
            public void run() {
                new JFXPanel(); // initializes JavaFX environment
                if (selectedShape.getClass().getSuperclass().getSimpleName()
                        .equals("TwoDimensionalShape")) {
                    Component shapePanel = (Component) new PaintedShape(selectedShape).getPanel();
                    drawing.add(shapePanel);
                } else {
                    JFXPanel shapePanel = (JFXPanel) new PaintedShape(selectedShape).getPanel();
                    Platform.runLater(() -> {
                        try {
                            SwingUtilities.invokeLater(() -> {
                                drawing.add(shapePanel);
                                frame.pack();
                            });

                        } catch (Exception e) {
                            e.printStackTrace();
                        }

                    });
                }
                drawingArea.removeAll();
                drawingArea.validate();
                drawingArea.add(drawing);
                drawingArea.repaint();
                frame.pack();
                frame.setSize(new Dimension((int) (frame.getSize().getWidth()),
                        (int) (frame.getSize().getHeight() + PaintedShape.size.getHeight())));
                frame.setLocationRelativeTo(null);
            }
        });
    }
});

完整的代码以及更改推送到 git 回购协议，以供更多好奇。

Swing/AWT/JavaFX 界面 Freezing/NullPointerException

Swing/AWT/JavaFX GUI Freezing/NullPointerException

java

swing

javafx

awt

nullpointerexception