How to mount a USB drive on Android Things?

问题

I'm attempting to read files off of a USB drive for an Android Things app on a Raspberry Pi. I'm able to scan the list of mounted devices like so:

public static List<File> ScanForFiles(Context context){
    ArrayList<File> files = new ArrayList<>();
    try{
        BufferedReader reader = new BufferedReader(new FileReader("/proc/self/mountinfo"));
        String line;
        while ((line = reader.readLine()) != null) {
            String[] columns = line.split(" ");
            Log.i(TAG, "Mounted: " + columns[4]);
            //files.addAll(getListFiles(new File(columns[4])));
        }
    } catch (Exception ex){
        ex.printStackTrace();
    }

    printFileInformation("/proc/partitions");

    return files;
}

private static void printFileInformation(String fileName){
    Log.i("TitanTV", "Reading contents of " + fileName);

    try{
        BufferedReader reader = new BufferedReader(new FileReader(fileName));
        String line;
        while ((line = reader.readLine()) != null){
            Log.i("TitanTV", line);
        }
    } catch (Exception ex){
        ex.printStackTrace();
    }
}

Which displays the following output:

I: Mounted: /
I: Mounted: /dev
I: Mounted: /dev
I: Mounted: /dev/pts
I: Mounted: /dev/memcg
I: Mounted: /dev/cpuctl
I: Mounted: /proc
I: Mounted: /sys
I: Mounted: /sys/fs/selinux
I: Mounted: /sys/fs/pstore
I: Mounted: /acct
I: Mounted: /mnt
I: Mounted: /mnt/runtime/default/emulated
I: Mounted: /mnt/runtime/read/emulated
I: Mounted: /mnt/runtime/write/emulated
I: Mounted: /config
I: Mounted: /data
I: Mounted: /oem
I: Mounted: /gapps
I: Mounted: /storage
I: Mounted: /storage/emulated
I: Mounted: /storage/self

I: Reading contents of /proc/partitions
I: major minor  #blocks  name
I:    1        0       8192 ram0
I:    1        1       8192 ram1
I:    1        2       8192 ram2
I:    1        3       8192 ram3
I:    1        4       8192 ram4
I:    1        5       8192 ram5
I:    1        6       8192 ram6
I:    1        7       8192 ram7
I:    1        8       8192 ram8
I:    1        9       8192 ram9
I:    1       10       8192 ram10
I:    1       11       8192 ram11
I:    1       12       8192 ram12
I:    1       13       8192 ram13
I:    1       14       8192 ram14
I:    1       15       8192 ram15
I:  179        0    7761920 mmcblk0
I:  179        1      65536 mmcblk0p1
I:  179        2       1024 mmcblk0p2
I:  179        3       1024 mmcblk0p3
I:  179        4      32768 mmcblk0p4
I:  179        5      32768 mmcblk0p5
I:  179        6     524288 mmcblk0p6
I:  179        7     524288 mmcblk0p7
I:  179        8         64 mmcblk0p8
I:  179        9         64 mmcblk0p9
I:  179       10       1024 mmcblk0p10
I:  179       11      32768 mmcblk0p11
I:  179       12      32768 mmcblk0p12
I:  179       13     262144 mmcblk0p13
I:  179       14     262144 mmcblk0p14
I:  179       15    2683736 mmcblk0p15
I:    8        0    7847935 sda
I:    8        1    7845888 sda1

However, my thumb drive isn't apart of the list. So I'm guessing I need to mount it in some way. How can I mount the thumb drive and access the files on it?

回答1:

ADB ONLY SOLUTION

Seem like as of now USB drives aren't mounted automatically. In order to make your code work I had to mount it manually.

As you can see (from /proc/partitions) in the /proc partition the USB drive is detected as sda.

ADB mounting

Make a directory to mount to
```
mkdir /mnt/usb
```

Mount the device

mount -t vfat -o rw /dev/block/sda1 /mnt/usb

Now you should be able to list (and manage) the files on the USB drive both via ADB and from within the app (/mnt/usb will also be logged).

回答2:

I think the only solution is to create a service in init.rc to be able to execute the script with root permisions on Boot. Apparently Android things doesnt have a solution right know. Something like:

on property:dev.bootcomplete=1

start bootcomplete_handler

service bootcomplete_handler /system/bin/sh /system/bin/bc_handler.sh

class late_start

user root

group root

disabled

oneshot

But dont know if this will work

回答3:

I have made an script that every 10 seconds if detects a usb storage units mounts it automatically, the only problem is to launch it on Boot, maybe this could help you, I have my post here: Execute Script on Boot Android Things

And the script:

while true; do

if [ "$( ls -l /dev/block/sd* | wc -l)" -ge 1 ];

then echo "partition available"

if [ "$( mount | grep  "usbAlv" -c)" -ge 1 ]; #if partition not mounted

then echo " Unit Mounted"

else

echo "not  mounted"


//if folder where we mount the partition doesnt exist

if [ !"$( ls -l /sdcard/usbAlv | wc -l)" -ge 1 ];

then mkdir /sdcard/usbAlv

fi

su root << EOSU

mount -t vfat -o rw /dev/block/sd* /sdcard/usbAlv

EOSU

fi

else

echo "not partition available"

fi

sleep 10;

done

Hope it helps, i guess now is the only posible way to do it programatically

来源：https://stackoverflow.com/questions/42465326/how-to-mount-a-usb-drive-on-android-things

标签

Linux

usb

mount

android-things