我正在读串口并正确绘制数据。我正在使用LineChart<Number, Number>系列来创建某个图表。有一种changeListener方法可以在数据进入时更新此系列。
在第二阶段，我正在使用网络摄像头通过openCV创建实时视频。我也在它上面叠了一条线。
该点，该行的一端取决于我LineChart<>系列的最后一个条目的数据。我正在使用以下代码来同步更新。它工作正常，但有时两个阶段都冻结，我得到这个错误：
Exception duting the image elaboration : java.lang.Exception: unknown exception
真的很奇怪。如果它不起作用，为什么不尽快或至少总是抛出这个例外？ 任何帮助表示赞赏。非常感谢。
代码很长。我刚发布相关的文章：
所有代码都在一个类中：
相关实例变量：
private Series<Number, Number> referenceSeries;
private Button activateCameraButton = new Button("Activate Camera");
private ImageView currentFrame = new ImageView();
private ScheduledExecutorService timer;
private VideoCapture capture = new VideoCapture();
private boolean cameraActive = false;
private ObjectProperty<Number> currentRefValNumber;
private double currentRefVal = 0;
在listner设置方法中：
currentRefValNumber = referenceSeries.dataProperty().get().get(
referenceSeries.getData().size() - 1).YValueProperty();
最后这里设置了网络摄像头视图部分：
private void setUpWebcamView() {
Stage secondStage = new Stage();
BorderPane root2 = new BorderPane();
activateCameraButton.setOnAction(e -> startCamera(e));
root2.setCenter(currentFrame);
root2.setTop(activateCameraButton);
root2.setId("webcamViewID");
//root2.getStylesheets().add("-fx-background-image: url('myimage.jpg')");
Scene scene2 = new Scene(root2, 800, 600);
scene2.getStylesheets().addAll(this.getClass().getResource("Style.css").toExternalForm());
secondStage .setTitle("webcam view");
secondStage .setScene(scene2);
secondStage .show();
}
private void startCamera(ActionEvent event) {
this.currentFrame.setPreserveRatio(true);
if (!this.cameraActive) {
this.capture.open(0);
if (this.capture.isOpened()) {
this.cameraActive = true;
Runnable frameGrabber = new Runnable() {
@Override
public void run() {
Image imageToShow = grabFrame();
currentFrame.setImage(imageToShow);
}
};
this.timer = Executors.newSingleThreadScheduledExecutor();
this.timer.scheduleAtFixedRate(frameGrabber, 0, 33, TimeUnit.MILLISECONDS);
this.activateCameraButton.setText("Stop Camera");
} else {
System.err.println("Camera Error");
}
} else {
this.cameraActive = false;
this.activateCameraButton.setText("Start Camera");
try {
this.timer.shutdown();
this.timer.awaitTermination(33, TimeUnit.MILLISECONDS);
} catch (InterruptedException e) {
System.err.println(
"Exceprion in stopping the frame capture, trying to stop the camera now....");
}
this.capture.release();
this.currentFrame.setImage(null);
}
}
private Image grabFrame() {
Image imageToShow = null;
Mat frame = new Mat();
if (this.capture.isOpened()) {
try {
this.capture.read(frame);
if (!frame.empty()) {
imageToShow = mat2Image(frame);
}
} catch (Exception e) {
System.err.println("Exception duting the image elaboration : " + e);
}
}
return imageToShow;
}
private Image mat2Image(Mat frame) {
Core.flip(frame, frame, 1);
currentRefVal = currentRefValNumber.getValue().doubleValue();
//System.out.println(currentRefVal);
Imgproc.line(frame, new Point(frame.size().width / 2, frame.size().height)
, new Point(frame.size().width / 2 - (frame.size().width / 40) * (currentRefVal), 0), new Scalar(0, 255, 0), 5);
MatOfByte buffer = new MatOfByte();
Imgcodecs.imencode(".bmp", frame, buffer);
return new Image(new ByteArrayInputStream(buffer.toArray()));
}
我再说一次，我的代码实际上有效，但并非总是如此。我正在系统化摄像头部分中的currentRefVal，它正在获取正确的数字。
更新
这是代码仍然有效的堆栈跟踪：
Exception duting the image elaboration : java.lang.NullPointerException
java.lang.NullPointerException
at myPackage.MainClass.mat2Image(MainClass.java:486)
at moradi.MainClass.grabFrame(MainClass.java:473)
at moradi.MainClass.access$0(MainClass.java:466)
at moradi.MainClass$1.run(MainClass.java:435)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
这是导致我的应用程序冻结和崩溃的堆栈跟踪
java.lang.Exception: unknown exception
at org.opencv.core.Mat.nGetB(Native Method)
at org.opencv.core.Mat.get(Mat.java:1013)
at org.opencv.core.MatOfByte.toArray(MatOfByte.java:58)
at myPackage.MainClass.mat2Image(MainClass.java:493)
at myPackage.MainClass.grabFrame(MainClass.java:473)
at myPackage.MainClass.access$0(MainClass.java:466)
at myPackage.MainClass$1.run(MainClass.java:435)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180)
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)