Android系統提供了Environment.getExternalStorageDirectory()介面獲得儲存裝置的路徑，但是這個介面往往給出的結果並不是我們想要的，在某些裝置上它返回的是手機內部儲存，某些裝置上返回的手機外部儲存。還有就是某些Android裝置支援擴充套件多個sdcard，這個時候想要獲得所有儲存器的掛載路徑，這個介面是沒有辦法辦到的。

那麼，Android系統的檔案管理器是如何把所有掛載的儲存裝置加載出來的呢？通過檢視檔案管理器的原始碼發現是在MountPointManager類中處理的，通過呼叫StorageManager類的getVolumeList()方法獲取的。

 /**
     * This method initializes MountPointManager.
     * 
     * @param context Context to use
     */
    public void init(Context context) {
        mStorageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
        final String defaultPath = getDefaultPath();
        LogUtils.d(TAG, "init,defaultPath = " + defaultPath);   
        if (!TextUtils.isEmpty(defaultPath)) {
            mRootPath = ROOT_PATH;
        }
        mMountPathList.clear();
        // check media availability to init mMountPathList
        StorageVolume[] storageVolumeList = mStorageManager.getVolumeList();
        if (storageVolumeList != null) {
            for (StorageVolume volume : storageVolumeList) {
                MountPoint mountPoint = new MountPoint();
                mountPoint.mDescription = volume.getDescription(context);
                mountPoint.mPath = volume.getPath();
                mountPoint.mIsMounted = isMounted(volume.getPath());
                mountPoint.mIsExternal = volume.isRemovable();
                mountPoint.mMaxFileSize = volume.getMaxFileSize();
                LogUtils.d(TAG, "init,description :" + mountPoint.mDescription + ",path : "
                        + mountPoint.mPath + ",isMounted : " + mountPoint.mIsMounted
                        + ",isExternal : " + mountPoint.mIsExternal + ", mMaxFileSize: " + mountPoint.mMaxFileSize);
                mMountPathList.add(mountPoint);
            }
        }
        IconManager.getInstance().init(context, defaultPath + SEPARATOR);
    }
 

    /**
     * Returns list of all mountable volumes.
     * @hide
     */
    public StorageVolume[] getVolumeList() {
        if (mMountService == null) return new StorageVolume[0];
        try {
            Parcelable[] list = mMountService.getVolumeList();
            if (list == null) return new StorageVolume[0];
            int length = list.length;
            StorageVolume[] result = new StorageVolume[length];
            for (int i = 0; i < length; i++) {
                result[i] = (StorageVolume)list[i];
            }
            return result;
        } catch (RemoteException e) {
            Log.e(TAG, "Failed to get volume list", e);
            return null;
        }
    }
 

通過反射機制獲取Android裝置的所有儲存裝置

public class StorageInfo {
	public String path;
	public String state;
	public boolean isRemoveable;
	public StorageInfo(String path) {
		this.path = path;
	}
	public boolean isMounted() {
		return "mounted".equals(state);
	}
	@Override
	public String toString() {
		return "StorageInfo [path=" + path + ", state=" + state
				+ ", isRemoveable=" + isRemoveable + "]";
	}
}

	public static List<StorageInfo> listAllStorage(Context context) {
		ArrayList<StorageInfo> storages = new ArrayList<StorageInfo>();
		StorageManager storageManager = (StorageManager) context.getSystemService(Context.STORAGE_SERVICE);
		try {
			Class<?>[] paramClasses = {};
			Method getVolumeList = StorageManager.class.getMethod("getVolumeList", paramClasses);
			Object[] params = {};
			Object[] invokes = (Object[]) getVolumeList.invoke(storageManager, params);
			
			if (invokes != null) {
				StorageInfo info = null;
				for (int i = 0; i < invokes.length; i++) {
					Object obj = invokes[i];
					Method getPath = obj.getClass().getMethod("getPath", new Class[0]);
					String path = (String) getPath.invoke(obj, new Object[0]);
					info = new StorageInfo(path);

					Method getVolumeState = StorageManager.class.getMethod("getVolumeState", String.class);
					String state = (String) getVolumeState.invoke(storageManager, info.path);
					info.state = state;

					Method isRemovable = obj.getClass().getMethod("isRemovable", new Class[0]);
					info.isRemoveable = ((Boolean) isRemovable.invoke(obj, new Object[0])).booleanValue();
					storages.add(info);
				}
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		storages.trimToSize();
		return storages;
	}
	
	public static List<StorageInfo> getAvaliableStorage(List<StorageInfo> infos){
		List<StorageInfo> storages = new ArrayList<StorageInfo>();
		for(StorageInfo info : infos){
			File file = new File(info.path);
			if ((file.exists()) && (file.isDirectory()) && (file.canWrite())) {
				if (info.isMounted()) {
					storages.add(info);
				}
			}
		}
		
		return storages;
	}

呼叫上述方法：

	List<StorageInfo> list = listAllStorage(this);
	for(StorageInfo info : list){
		Log.e(TAG, info.toString());
	}
	Log.e(TAG, "-----------------");
	List<StorageInfo> infos = getAvaliableStorage(list);
	for(StorageInfo info : infos){
		Log.e(TAG, info.toString());
	}
	
	Log.e(TAG, "Environment.getExternalStorageDirectory(): " + Environment.getExternalStorageDirectory());

連上手機進行驗證，輸出Log資訊：

可以看到，通過listAllStorage()方法獲取到了手機上的所有儲存裝置，通過getAvaliableStorage()方法的過濾獲取到了掛載狀態的所有儲存裝置。由於該手機只有一個可讀寫的儲存裝置，因此與Environment.getExternalStorageDirectory()方法獲取到的結果一致。

注意：由於在getAvaliableStorage()方法中我們獲取的是可寫（canWrite）的裝置，需要加上相應許可權： <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> ，否則獲取不到儲存裝置。