Java libusb无法取消上下文初始化
我需要一些关于Java中非法状态异常的帮助。 我有一个可以从USB设备读取数据的源代码 该代码尚未完成,但我已经得到以下错误报告Java libusb无法取消上下文初始化,java,usb,libusb,Java,Usb,Libusb,我需要一些关于Java中非法状态异常的帮助。 我有一个可以从USB设备读取数据的源代码 该代码尚未完成,但我已经得到以下错误报告 Exception in thread "main" java.lang.IllegalStateException: default context is not initialized at org.usb4java.Libusb.exit(Native Method) at testnew.main(testnew.java:122) 第122行是LibUs
Exception in thread "main" java.lang.IllegalStateException: default context is not initialized at org.usb4java.Libusb.exit(Native Method) at testnew.main(testnew.java:122)
第122行是LibUsb.exit(null)
代码如下
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.IntBuffer;
import javax.usb.UsbConfiguration;
import javax.usb.UsbDevice;
import javax.usb.UsbDeviceDescriptor;
import javax.usb.UsbDisconnectedException;
import javax.usb.UsbException;
import javax.usb.UsbHostManager;
import javax.usb.UsbHub;
import javax.usb.UsbInterface;
import javax.usb.UsbInterfacePolicy;
import javax.usb.UsbNotActiveException;
import javax.usb.event.UsbPipeDataEvent;
import javax.usb.event.UsbPipeErrorEvent;
import javax.usb.event.UsbPipeListener;
import org.usb4java.BufferUtils;
import org.usb4java.DeviceHandle;
import org.usb4java.LibUsb;
import org.usb4java.LibUsbException;
public class testnew {
private final static short VENDOR_ID = 0x0403;
private final static short PRODUCT_ID = 0x6001;
private static byte IN_ENDPOINT = (byte) 0x81;
private static long TIMEOUT = 5000;
private final static int INTERFACE = 0;
private final static Object CONNECT_HEADER = 000;
private final static Object CONNECT_BODY = 000;
public static UsbDevice getHygrometerDevice(UsbHub hub) {
UsbDevice launcher = null;
for (Object object : hub.getAttachedUsbDevices()) {
UsbDevice device = (UsbDevice) object;
if (device.isUsbHub()) {
launcher = getHygrometerDevice((UsbHub) device);
if (launcher != null)
return launcher;
} else {
UsbDeviceDescriptor desc = device.getUsbDeviceDescriptor();
if (desc.idVendor() == VENDOR_ID && desc.idProduct() == PRODUCT_ID)
return device;
}
}
return null;
}
public static char readKey() {
try {
String line = new BufferedReader(new InputStreamReader(System.in)).readLine();
if (line.length() > 0)
return line.charAt(0);
return 0;
} catch (IOException e) {
throw new RuntimeException("Unable to read key", e);
}
}
public static ByteBuffer read(DeviceHandle handle, int size) {
ByteBuffer buffer = BufferUtils.allocateByteBuffer(size).order(ByteOrder.LITTLE_ENDIAN);
IntBuffer transferred = BufferUtils.allocateIntBuffer();
int result = LibUsb.bulkTransfer(handle, IN_ENDPOINT, buffer, transferred, TIMEOUT);
if (result != LibUsb.SUCCESS) {
throw new LibUsbException("Unable to read data", result);
}
System.out.println(transferred.get() + " bytes read from device");
return buffer;
}
public static void main(String[] args) {
// Search for the missile launcher USB device and stop when not found
UsbDevice device;
try {
device = getHygrometerDevice(UsbHostManager.getUsbServices().getRootUsbHub());
if (device == null) {
System.err.println("Missile launcher not found.");
System.exit(1);
return;
}
// Claim the interface
UsbConfiguration configuration = device.getUsbConfiguration((byte) 1);
UsbInterface iface = configuration.getUsbInterface((byte) INTERFACE);
iface.claim(new UsbInterfacePolicy() {
@Override
public boolean forceClaim(UsbInterface usbInterface) {
return true;
}
});
iface.getUsbEndpoint(IN_ENDPOINT).getUsbPipe().addUsbPipeListener(new UsbPipeListener() {
@Override
public void errorEventOccurred(UsbPipeErrorEvent arg0) {
// TODO Auto-generated method stub
}
@Override
public void dataEventOccurred(UsbPipeDataEvent arg0) {
for (byte b : arg0.getData())
System.out.print(b);
System.out.print("\n");
}
});
;
} catch (UsbNotActiveException | UsbDisconnectedException | UsbException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// Deinitialize the libusb context
LibUsb.exit(null);
}
}
有什么建议吗?您没有初始化上下文,这就是您在尝试取消初始化时出错的原因,请参见示例17
public static void main(String[] args)
{
//Initialize the libusb context
int result = LibUsb.Init(null);
if (result != LibUsb.SUCCESS){
throw new LibUsbException("Unable to initialze libusb",result);
}
[...]
如何打开管道取决于要选择的传输类型(批量传输、同步传输、异步传输),请参阅
对于同步传输,您可以使用(复制自)
有IN端点和OUT端点,您可以向OUT写入数据,也可以从IN读取数据。控制传输到EP0。所有USB通信都由主机设备启动,这意味着USB设备甚至无法启动通信
有关USB协议的详细信息,请参见好的,明白了。那是个简单的错误。。我该怎么继续下去?我想从管道里读出数据。。但首先我得打开管道。。哪里我如何读出数据?
UsbEndpoint endpoint = iface.getUsbEndpoint((byte) 0x83);
UsbPipe pipe = endpoint.getUsbPipe();
pipe.open();
try
{
byte[] data = new byte[8];
int received = pipe.syncSubmit(data);
System.out.println(received + " bytes received");
}
finally
{
pipe.close();
}