java - JavaFX 稍后运行不起作用

Question

我正在执行 Platform.RunLater 来更新 TextField。在这里你可以看到代码:

public class FXMLDocumentController implements Initializable {

    @FXML
    private TextField carlos;
    RXTX main = new RXTX();

    public void Test(){
    Platform.runLater(new Runnable() {
                    @Override public void run() {
                        carlos.setText("Test");    
                  }
                });

    }



    @Override
    public void initialize(URL url, ResourceBundle rb) {
        main.initialize();
        Thread t=new Thread() {
            public void run() {
                //the following line will keep this app alive for 1000 seconds,
                //waiting for events to occur and responding to them (printing incoming messages to console).
                try {Thread.sleep(1000000);} catch (InterruptedException ie) {}
            }
        };
        t.start();
        System.out.println("Started");
    }    

}

还有:

public class RXTX implements SerialPortEventListener{


    private String Temperature;

        SerialPort serialPort;
        /** The port we're normally going to use. */
    private static final String PORT_NAMES[] = { 
            "COM4" // Windows
    };
    /**
    * A BufferedReader which will be fed by a InputStreamReader 
    * converting the bytes into characters 
    * making the displayed results codepage independent
    */
    private BufferedReader input;
    /** The output stream to the port */
    private OutputStream output;
    /** Milliseconds to block while waiting for port open */
    private static final int TIME_OUT = 2000;
    /** Default bits per second for COM port. */
    private static final int DATA_RATE = 9600;

    public void initialize() {
        CommPortIdentifier portId = null;
        Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();

        //First, Find an instance of serial port as set in PORT_NAMES.
        while (portEnum.hasMoreElements()) {
            CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
            for (String portName : PORT_NAMES) {
                if (currPortId.getName().equals(portName)) {
                    portId = currPortId;
                    break;
                }
            }
        }
        if (portId == null) {
            System.out.println("Could not find COM port.");
            return;
        }

        try {
            // open serial port, and use class name for the appName.
            serialPort = (SerialPort) portId.open(this.getClass().getName(),
                    TIME_OUT);

            // set port parameters
            serialPort.setSerialPortParams(DATA_RATE,
                    SerialPort.DATABITS_8,
                    SerialPort.STOPBITS_1,
                    SerialPort.PARITY_NONE);

            // open the streams
            input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
            output = serialPort.getOutputStream();

            // add event listeners
            serialPort.addEventListener(this);
            serialPort.notifyOnDataAvailable(true);
        } catch (Exception e) {
            System.err.println(e.toString());
        }
    }

    /**
     * This should be called when you stop using the port.
     * This will prevent port locking on platforms like Linux.
     */
    public synchronized void close() {
        if (serialPort != null) {
            serialPort.removeEventListener();
            serialPort.close();
        }
    }

    /**
     * Handle an event on the serial port. Read the data and print it.
     */
    public synchronized void serialEvent(SerialPortEvent oEvent) {
        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                String inputLine=input.readLine();
                System.out.println(inputLine);
                                GetData(inputLine);
            } catch (Exception e) {
                System.err.println(e.toString());
            }
        }
        // Ignore all the other eventTypes, but you should consider the other ones.
    }

        @FXML
    private void GetData(String Data) {

            if(Data.contains("Temperature")){
                FXMLDocumentController main = new FXMLDocumentController();
                main.Test();
            }

        }
}

好吧，所以我不工作。它返回这样的错误:

Exception in runnable java.lang.NullPointerException at openpilot.FXMLDocumentController$1.run(FXMLDocumentController.java:35) at com.sun.javafx.application.PlatformImpl$4$1.run(PlatformImpl.java:182) at com.sun.javafx.application.PlatformImpl$4$1.run(PlatformImpl.java:179) at java.security.AccessController.doPrivileged(Native Method) at com.sun.javafx.application.PlatformImpl$4.run(PlatformImpl.java:179) at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:76) at com.sun.glass.ui.win.WinApplication._runLoop(Native Method) at com.sun.glass.ui.win.WinApplication.access$100(WinApplication.java:17) at com.sun.glass.ui.win.WinApplication$3$1.run(WinApplication.java:67) at java.lang.Thread.run(Thread.java:744)

Answer 1

不要使用new创建FXML Controller ，使用FXMLLoader.load() .

在您的特定情况下，最好使用 Platform.runLater() 在 JavaFX 应用程序线程上调用 load()。

FXMLLoader 创建 @FXML 注释节点的实例。因此，除非您使用加载器，否则永远不会创建 @FXML 节点。因此，在这种情况下，您的“carlos”TextField 为 null，因为没有任何东西创建这样的 TextField，从而导致 NullPointerException。

NullPointerException 错误与 runLater 是否工作无关。

您的代码中可能还存在很多其他错误。

我建议先花更多时间编写基本的单线程 JavaFX 应用程序，然后再处理与串行端口通信的多线程应用程序。