Java: List Cameras that are Plugged In

问题:

My program currently gets a list of drives plugged into the computer with File.listRoots(). But, when I plug a camera or an MP3 player into the computer directly (instead of inserting the memory card), it's not listed, nor does it have a drive letter in Windows Explorer. For example, here's the location of my camera:

Computer\Canon PowerShot SD750\Removable storage

How can I also list cameras/other devices that do not have a drive letter? I assume this will require a JNI library of some sort, but I don't know for sure obviously.

Thanks!

P.S. Out of desperation, I did try to list the contents of Computer\; it didn't work of course.

---

Update: I found this question here: Portable Device Path on Windows ; that's exactly the problem I'm having, but there is no solution laid out there.

回答1:

Java 7 has some promising looking classes in this area, like this one: http://download.java.net/jdk7/docs/api/java/nio/file/FileSystem.html

Assuming that you need it to work on Java 6 as well, I would suggest running a shell script and parsing its output. On Windows you could run mountvol, on Unix/MacOS X mount etc. Of course parsing the output would be somewhat tedious and you would have to worry about every OS your app runs on, but hey, at least... not sure what.... it works?

Here is some sample code which seems helpful on Windows:

strComputer = "."
Set objWMIService = GetObject("winmgmts:" _
    & "{impersonationLevel=impersonate}!\\" & strComputer & "\root\cimv2")

Set colItems = objWMIService.ExecQuery("Select * from Win32_Volume")

For Each objItem In colItems
    WScript.Echo "Automount: " & objItem.Automount
    WScript.Echo "Block Size: " & objItem.BlockSize
    WScript.Echo "Capacity: " & objItem.Capacity
    WScript.Echo "Caption: " & objItem.Caption
    WScript.Echo "Compressed: " & objItem.Compressed
    WScript.Echo "Device ID: " & objItem.DeviceID
    WScript.Echo "Dirty Bit Set: " & objItem.DirtyBitSet
    WScript.Echo "Drive Letter: " & objItem.DriveLetter
    WScript.Echo "Drive Type: " & objItem.DriveType
    WScript.Echo "File System: " & objItem.FileSystem
    WScript.Echo "Free Space: " & objItem.FreeSpace
    WScript.Echo "Indexing Enabled: " & objItem.IndexingEnabled
    WScript.Echo "Label: " & objItem.Label
    WScript.Echo "Maximum File Name Length: " & objItem.MaximumFileNameLength
    WScript.Echo "Name: " & objItem.Name
    WScript.Echo "Quotas Enabled: " & objItem.QuotasEnabled
    WScript.Echo "Quotas Incomplete: " & objItem.QuotasIncomplete
    WScript.Echo "Quotas Rebuilding: " & objItem.QuotasRebuilding
    WScript.Echo "Serial Number: " & objItem.SerialNumber
    WScript.Echo "Supports Disk Quotas: " & objItem.SupportsDiskQuotas
    WScript.Echo "Supports File-Based Compression: " & _
        objItem.SupportsFileBasedCompression
    WScript.Echo
Next

Here is the output I got for my ebook reader:

Automount: True
Block Size: 4096
Capacity: 999120896
Caption: G:\
Compressed: 
Device ID: \\?\Volume{8e3b4ce5-a124-11e0-9d2b-e30c5839642d}\
Dirty Bit Set: False
Drive Letter: G:
Drive Type: 2
File System: FAT32
Free Space: 663683072
Indexing Enabled: 
Label: PocketBook9
Maximum File Name Length: 255
Name: G:\
Quotas Enabled: 
Quotas Incomplete: 
Quotas Rebuilding: 
Serial Number: 1276177233
Supports Disk Quotas: False
Supports File-Based Compression: False

回答2:

The solution to above problem using JMTP library on

http://code.google.com/p/jmtp/

Here is my code

    package jmtp;


import be.derycke.pieter.com.COMException;
import be.derycke.pieter.com.Guid;
import java.io.*;
import java.math.BigInteger;
import jmtp.PortableDevice;
import jmtp.*;

public class Jmtp {

    public static void main(String[] args) {
        PortableDeviceManager manager = new PortableDeviceManager();
        PortableDevice device = manager.getDevices()[0];
        // Connect to my mp3-player
        device.open();

        System.out.println(device.getModel());

        System.out.println("---------------");

        // Iterate over deviceObjects
        for (PortableDeviceObject object : device.getRootObjects()) {
            // If the object is a storage object
            if (object instanceof PortableDeviceStorageObject) {
                PortableDeviceStorageObject storage = (PortableDeviceStorageObject) object;

                for (PortableDeviceObject o2 : storage.getChildObjects()) {
//                    
//                        BigInteger bigInteger1 = new BigInteger("123456789");
//                        File file = new File("c:/JavaAppletSigningGuide.pdf");
//                        try {
//                            storage.addAudioObject(file, "jj", "jj", bigInteger1);
//                        } catch (Exception e) {
//                            //System.out.println("Exception e = " + e);
//                        }
//                    

                    System.out.println(o2.getOriginalFileName());
                }
            }
        }

        manager.getDevices()[0].close();

    }
}

Donot forget add jmtp.dll files (that comes up with jmtp download) as a native library for more info see my answer on

http://stackoverflow.com/questions/12798530/including-native-library-in-netbeans

回答3:

This may not be the answer you're looking for, but is assigning them to a drive letter not an option? You can usually manually do this with USB devices on Windows using My Computer > right-click > Manage > Storage.

It's possible that CaptureDeviceManager in JMF (java media framework) could help you but I kind of doubt it.

回答4:

Maybe you can take a look at Morena Framework http://www.gnome.sk/Twain/jtp.htmlv (seems to be open source, but a little expensive; though there is a free evaluation version), it is for TWAIN compatible scanners/cameras (Windows/MAC) or SANE compatible (Linux or other unix flavor), to get a list of connected devices, you can do this:

import SK.gnome.morena.*;
import SK.gnome.twain.*;

public class Test
{
    public static void main(String[] args) throws Exception
    {
        TwainSource[] sources=TwainManager.listSources();
        if(sources == null) return;
        for(int i = 0; i < sources.length; i++)
        {
            System.out.println("Twain source is: " + ts.toString());
        }
    }
}

Maybe that could help,if not I think maybe JMF is a possible solution.