java如何等待Canvas/GraphicsContext完成任务，然后再继续执行代码块？

Question

如何强制GraphicsContext或Canvas等待绘图任务完成，然后再继续向下块

GraphicsContext gc = canvas.getGraphicsContext2D();

gc.clearRect(0, 0, width, height);
gc.drawImage(pause, firstImageX, y);
gc.drawImage(cancel, leftImageX, y);
gc.drawImage(complete, rightImageX, y);

Platform.runLater(() -> {
     try {
         gc.wait();
     } catch (InterruptedException e) {
         e.printStackTrace();
     }
});

//other stuff

我试过了

try {
     gc.wait();
} catch (InterruptedException e) {
     e.printStackTrace();
}

它确实更新了画布，但我得到了一个错误

Exception in thread "JavaFX Application Thread" java.lang.IllegalMonitorStateException
at java.lang.Object.wait(Native Method)
at java.lang.Object.wait(Object.java:502)
at captureGIF.CaptureGIF.lambda$null$6(CaptureGIF.java:176)
at com.sun.javafx.application.PlatformImpl.lambda$null$173(PlatformImpl.java:295)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.application.PlatformImpl.lambda$runLater$174(PlatformImpl.java:294)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$148(WinApplication.java:191)
at java.lang.Thread.run(Thread.java:745)

谢谢