usb4java USB错误4:无法打开USB设备：

Question

我正在尝试与PS3的DS3控制器接口。我在C#中成功地使用了libusb的实现，但决定将实现转移到java。不幸的是，我对java的迁移并不是那么顺利。设备似乎在设备列表中找到，但当我试图打开它时，我得到以下错误“USB错误4:无法打开USB设备:没有这样的设备(可能已断开连接)”

public class Main {
private static final short VID = 0x054c;
private static final short PID = 0x0268;

Context context;

public Main() {
    context = new Context();
    int result = LibUsb.init(context);

    if (result != LibUsb.SUCCESS) {
        throw new LibUsbException("Unable to initialize libusb.", result);
    }

    ByteBuffer data = ByteBuffer.allocate(49);
    DeviceHandle ds3Handle = getDeviceHandle(findDevice(VID, PID));
    LibUsb.controlTransfer(ds3Handle, (byte)0xa1, (byte)0x1, (short)0x101, (short)0, data, 1000L);

    LibUsb.exit(context);
}

private Device findDevice(int vid, int pid) {
    Device UsbDevice = null;
    DeviceList list = new DeviceList();
    int result = LibUsb.getDeviceList(context, list);

    if (result < 0) {
        throw new LibUsbException("Unable to get device list", result);
    } 

    try {
        for(Device device: list) {
            DeviceDescriptor descriptor = new DeviceDescriptor();
            result = LibUsb.getDeviceDescriptor(device, descriptor);

            if (result != LibUsb.SUCCESS) {
                throw new LibUsbException("Unable to read device descriptor", result);
            } 

            if (descriptor.idVendor() == vid && descriptor.idProduct() == pid) {
                UsbDevice = device;
                System.out.println("found");
            }
        }
    } finally {
        LibUsb.freeDeviceList(list, true);
    }

    return UsbDevice;
}

private DeviceHandle getDeviceHandle(Device device) {
    DeviceHandle handle = new DeviceHandle();
    int result = LibUsb.open(device, handle);

    if (result != LibUsb.SUCCESS) {
        throw new LibUsbException("Unable to open USB device", result);
    }

    return handle;
}

public static void main(String [] args){
    new Main();
}
}

Answer 1

LibUsb.freeDeviceList(列表，真)；

true就是问题所在。“最终布尔unrefDevices”在javadoc中显示。在您有机会打开设备之前，您的代码正在释放该设备。

Answer 2

只更改为false是不够的，您还需要用需要返回示例的设备调用refDevice：

    } finally {
        // Ensure the allocated device list is freed
        LibUsb.freeDeviceList(list, false);
    }

    if (deviceFound != null) {
        // Device found
        LibUsb.refDevice(deviceFound);
    }
    return deviceFound;