我找到的唯一有效的解决方案是使用反射

 /**
 * Get external sd card path using reflection
 * @param mContext
 * @param is_removable is external storage removable
 * @return
 */
private static String getExternalStoragePath(Context mContext, boolean is_removable) {

    StorageManager mStorageManager = (StorageManager) mContext.getSystemService(Context.STORAGE_SERVICE);
    Class<?> storageVolumeClazz = null;
    try {
        storageVolumeClazz = Class.forName("android.os.storage.StorageVolume");
        Method getVolumeList = mStorageManager.getClass().getMethod("getVolumeList");
        Method getPath = storageVolumeClazz.getMethod("getPath");
        Method isRemovable = storageVolumeClazz.getMethod("isRemovable");
        Object result = getVolumeList.invoke(mStorageManager);
        final int length = Array.getLength(result);
        for (int i = 0; i < length; i++) {
            Object storageVolumeElement = Array.get(result, i);
            String path = (String) getPath.invoke(storageVolumeElement);
            boolean removable = (Boolean) isRemovable.invoke(storageVolumeElement);
            if (is_removable == removable) {
                return path;
            }
        }
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    } catch (InvocationTargetException e) {
        e.printStackTrace();
    } catch (NoSuchMethodException e) {
        e.printStackTrace();
    } catch (IllegalAccessException e) {
        e.printStackTrace();
    }
    return null;
}

这个解决方案处理System.getenv(“SECONDARY_STORAGE”)在Marshmallow中没有用的问题。

已测试和正在进行:

Samsung Galaxy Tab 2 (Android 4.1.1 - Stock) Samsung Galaxy Note 8.0 (Android 4.2.2 - Stock) Samsung Galaxy S4 (Android 4.4 - Stock) Samsung Galaxy S4 (Android 5.1.1 - Cyanogenmod) Samsung Galaxy Tab A (Android 6.0.1 - Stock) /** * Returns all available external SD-Card roots in the system. * * @return paths to all available external SD-Card roots in the system. */ public static String[] getStorageDirectories() { String [] storageDirectories; String rawSecondaryStoragesStr = System.getenv("SECONDARY_STORAGE"); if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) { List<String> results = new ArrayList<String>(); File[] externalDirs = applicationContext.getExternalFilesDirs(null); for (File file : externalDirs) { String path = file.getPath().split("/Android")[0]; if((Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP && Environment.isExternalStorageRemovable(file)) || rawSecondaryStoragesStr != null && rawSecondaryStoragesStr.contains(path)){ results.add(path); } } storageDirectories = results.toArray(new String[0]); }else{ final Set<String> rv = new HashSet<String>(); if (!TextUtils.isEmpty(rawSecondaryStoragesStr)) { final String[] rawSecondaryStorages = rawSecondaryStoragesStr.split(File.pathSeparator); Collections.addAll(rv, rawSecondaryStorages); } storageDirectories = rv.toArray(new String[rv.size()]); } return storageDirectories; }

这么晚了，但最终我得到了一些东西，我已经测试了大多数设备(通过制造商和android版本)，它在android 2.2+上工作。如果您发现它不起作用，请用您的设备名称注释它。我会解决的。如果有人感兴趣，我会解释它是如何工作的。

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FilenameFilter;
import java.io.IOException;
import java.io.InputStreamReader;

import android.util.Log;


/**
 * @author ajeet
 *05-Dec-2014  2014
 *
 */
public class StorageUtil {

    public boolean isRemovebleSDCardMounted() {
        File file = new File("/sys/class/block/");
        File[] files = file.listFiles(new MmcblkFilter("mmcblk\\d$"));
        boolean flag = false;
        for (File mmcfile : files) {
            File scrfile = new File(mmcfile, "device/scr");
            if (scrfile.exists()) {
                flag = true;
                break;
            }
        }
        return flag;
    }

    public String getRemovebleSDCardPath() throws IOException {
        String sdpath = null;
        File file = new File("/sys/class/block/");
        File[] files = file.listFiles(new MmcblkFilter("mmcblk\\d$"));
        String sdcardDevfile = null;
        for (File mmcfile : files) {
            Log.d("SDCARD", mmcfile.getAbsolutePath());
            File scrfile = new File(mmcfile, "device/scr");
            if (scrfile.exists()) {
                sdcardDevfile = mmcfile.getName();
                Log.d("SDCARD", mmcfile.getName());
                break;
            }
        }
        if (sdcardDevfile == null) {
            return null;
        }
        FileInputStream is;
        BufferedReader reader;

        files = file.listFiles(new MmcblkFilter(sdcardDevfile + "p\\d+"));
        String deviceName = null;
        if (files.length > 0) {
            Log.d("SDCARD", files[0].getAbsolutePath());
            File devfile = new File(files[0], "dev");
            if (devfile.exists()) {
                FileInputStream fis = new FileInputStream(devfile);
                reader = new BufferedReader(new InputStreamReader(fis));
                String line = reader.readLine();
                deviceName = line;
            }
            Log.d("SDCARD", "" + deviceName);
            if (deviceName == null) {
                return null;
            }
            Log.d("SDCARD", deviceName);

            final File mountFile = new File("/proc/self/mountinfo");

            if (mountFile.exists()) {
                is = new FileInputStream(mountFile);
                reader = new BufferedReader(new InputStreamReader(is));
                String line = null;
                while ((line = reader.readLine()) != null) {
                    // Log.d("SDCARD", line);
                    // line = reader.readLine();
                    // Log.d("SDCARD", line);
                    String[] mPonts = line.split("\\s+");
                    if (mPonts.length > 6) {
                        if (mPonts[2].trim().equalsIgnoreCase(deviceName)) {
                            if (mPonts[4].contains(".android_secure")
                                    || mPonts[4].contains("asec")) {
                                continue;
                            }
                            sdpath = mPonts[4];
                            Log.d("SDCARD", mPonts[4]);

                        }
                    }

                }
            }

        }

        return sdpath;
    }

    static class MmcblkFilter implements FilenameFilter {
        private String pattern;

        public MmcblkFilter(String pattern) {
            this.pattern = pattern;

        }

        @Override
        public boolean accept(File dir, String filename) {
            if (filename.matches(pattern)) {
                return true;
            }
            return false;
        }

    }

}

根据这里找到的一些答案，我想出了以下解决方案。

代码:

public class ExternalStorage {

    public static final String SD_CARD = "sdCard";
    public static final String EXTERNAL_SD_CARD = "externalSdCard";

    /**
     * @return True if the external storage is available. False otherwise.
     */
    public static boolean isAvailable() {
        String state = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(state) || Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
            return true;
        }
        return false;
    }

    public static String getSdCardPath() {
        return Environment.getExternalStorageDirectory().getPath() + "/";
    }

    /**
     * @return True if the external storage is writable. False otherwise.
     */
    public static boolean isWritable() {
        String state = Environment.getExternalStorageState();
        if (Environment.MEDIA_MOUNTED.equals(state)) {
            return true;
        }
        return false;

    }

    /**
     * @return A map of all storage locations available
     */
    public static Map<String, File> getAllStorageLocations() {
        Map<String, File> map = new HashMap<String, File>(10);

        List<String> mMounts = new ArrayList<String>(10);
        List<String> mVold = new ArrayList<String>(10);
        mMounts.add("/mnt/sdcard");
        mVold.add("/mnt/sdcard");

        try {
            File mountFile = new File("/proc/mounts");
            if(mountFile.exists()){
                Scanner scanner = new Scanner(mountFile);
                while (scanner.hasNext()) {
                    String line = scanner.nextLine();
                    if (line.startsWith("/dev/block/vold/")) {
                        String[] lineElements = line.split(" ");
                        String element = lineElements[1];

                        // don't add the default mount path
                        // it's already in the list.
                        if (!element.equals("/mnt/sdcard"))
                            mMounts.add(element);
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        try {
            File voldFile = new File("/system/etc/vold.fstab");
            if(voldFile.exists()){
                Scanner scanner = new Scanner(voldFile);
                while (scanner.hasNext()) {
                    String line = scanner.nextLine();
                    if (line.startsWith("dev_mount")) {
                        String[] lineElements = line.split(" ");
                        String element = lineElements[2];

                        if (element.contains(":"))
                            element = element.substring(0, element.indexOf(":"));
                        if (!element.equals("/mnt/sdcard"))
                            mVold.add(element);
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }


        for (int i = 0; i < mMounts.size(); i++) {
            String mount = mMounts.get(i);
            if (!mVold.contains(mount))
                mMounts.remove(i--);
        }
        mVold.clear();

        List<String> mountHash = new ArrayList<String>(10);

        for(String mount : mMounts){
            File root = new File(mount);
            if (root.exists() && root.isDirectory() && root.canWrite()) {
                File[] list = root.listFiles();
                String hash = "[";
                if(list!=null){
                    for(File f : list){
                        hash += f.getName().hashCode()+":"+f.length()+", ";
                    }
                }
                hash += "]";
                if(!mountHash.contains(hash)){
                    String key = SD_CARD + "_" + map.size();
                    if (map.size() == 0) {
                        key = SD_CARD;
                    } else if (map.size() == 1) {
                        key = EXTERNAL_SD_CARD;
                    }
                    mountHash.add(hash);
                    map.put(key, root);
                }
            }
        }

        mMounts.clear();

        if(map.isEmpty()){
                 map.put(SD_CARD, Environment.getExternalStorageDirectory());
        }
        return map;
    }
}

用法:

Map<String, File> externalLocations = ExternalStorage.getAllStorageLocations();
File sdCard = externalLocations.get(ExternalStorage.SD_CARD);
File externalSdCard = externalLocations.get(ExternalStorage.EXTERNAL_SD_CARD);

如果你看一下Android .os. environment的源代码，你会发现Android非常依赖环境变量作为路径。您可以使用“SECONDARY_STORAGE”环境变量来查找到可移动sd卡的路径。

/**
 * Get a file using an environmental variable.
 *
 * @param variableName
 *         The Environment variable name.
 * @param paths
 *         Any paths to the file if the Environment variable was not found.
 * @return the File or {@code null} if the File could not be located.
 */
private static File getDirectory(String variableName, String... paths) {
    String path = System.getenv(variableName);
    if (!TextUtils.isEmpty(path)) {
        if (path.contains(":")) {
            for (String _path : path.split(":")) {
                File file = new File(_path);
                if (file.exists()) {
                    return file;
                }
            }
        } else {
            File file = new File(path);
            if (file.exists()) {
                return file;
            }
        }
    }
    if (paths != null && paths.length > 0) {
        for (String _path : paths) {
            File file = new File(_path);
            if (file.exists()) {
                return file;
            }
        }
    }
    return null;
}

使用示例:

public static final File REMOVABLE_STORAGE = getDirectory("SECONDARY_STORAGE");

这是我用来找到外部卡的方法。使用mount cmd返回然后解析vfat部分。

String s = "";
try {
Process process = new ProcessBuilder().command("mount")
        .redirectErrorStream(true).start();

process.waitFor();

InputStream is = process.getInputStream();
byte[] buffer = new byte[1024];
while (is.read(buffer) != -1) {
    s = s + new String(buffer);
}
is.close();
} catch (Exception e) {
e.printStackTrace();
}

//用行分隔mount列表
String[] lines = s.split("\n");
for(int i=0; i<lines.length; i++) {
//如果行内有挂载路径且为vfat类型，说明可能是内置或者外置sd的挂载点
if(-1 != lines[i].indexOf(path[0]) && -1 != lines[i].indexOf("vfat")) {
    //再用空格分隔
    String[] blocks = lines[i].split("\\s");
    for(int j=0; j<blocks.length; j++) {
        //判断是否是挂载为vfat类型
        if(-1 != blocks[j].indexOf(path[0])) {
            //Test if it is the external sd card.
        }
    }
}
}