Check for file existence in androids assets folder?

Question

My app has .txt files in subdirectories in the assets folder. It reads those .txt files and puts them in a textview. It's working great and no problems.

Should I be concerned about the files in the assets folder getting deleted by the user or missing. If this ever could happen, my app would get an error because the file would not be there when it tried to read it into the stream.

Is there a need for me to check the existence of an asset file before I read it or does the asset manager take care of it all? I also was wondering if there's a chance that a user would or could delete and asset file.

Like I say, everything works fine without me inserting code to check for file existence. I just wondered if people use the .exists() statement every time they go to read in a stream from assets.

score 81 · Answer 1 · answered Sep 07 '11 at 16:43

81

You may be concerned that the file have been removed and the apk resigned

You can check using:

Arrays.asList(getResources().getAssets().list("")).contains("myFile")

answered Sep 07 '11 at 16:43

njzk2

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It works when you have unique files names, otherwise use natronite solution. – IliaEremin Nov 11 '15 at 18:06
I'm designing a generic app as a sort of template, which may or may not have some embedded files. This solution works great for me, thanks! :) – monkey0506 Feb 03 '16 at 22:30
1

@IlyaEremin non-unique filenames. I'm curious to see how that works. – njzk2 Feb 03 '16 at 22:48
process is so slow. – Ahamadullah Saikat Sep 03 '19 at 10:27
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This solution doesn't list the files inside sub-folders! – Mostafa Arian Nejad Jan 03 '21 at 04:32
@Mostafa Arian Nejad Replace the string parameter of list() with the path to the subfolder. – harveyhans Aug 07 '21 at 01:54

score 32 · Answer 2 · edited Jan 20 '17 at 10:16

32

if you really want to check for the file existence:

AssetManager mg = getResources().getAssets();
InputStream is = null;
try {
  is = mg.open(pathInAssets);
  //File exists so do something with it
} catch (IOException ex) {
  //file does not exist
} finally {
  if (is != null) {
    is.close();
  }
}

If your file is located in assets/folder/file.ext, then pathInAssets would be "folder/file.ext"

edited Jan 20 '17 at 10:16

Tim Kist

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answered Mar 31 '11 at 09:53

natronite

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If it does not fail you should close the opened stream. – Moss Nov 09 '11 at 19:26
Well, it isn't being saved as a reference, so the returned inputstream should be cleaned out at the end of the method call anyhow – programmer33 Oct 21 '12 at 16:13

Shridutt Kothari · Answer 3 · 2016-07-07T08:07:41.057

Ideally after apk is built, nobody can remove any assets from it, but if someone decompiled it and recompiles than it may be possible.

Though for other scenarios also when an asset is not present in apk at Runtime, we can check the existence of asset.

In our app, we have a provision to build app using gradle, ant and eclipse, and for each build mechanism some of our assets file are bundled in apk and some are not, so to identify if any asset file is present in current build apk at runtime,

we do this as follows:

private boolean isAssetExists(String pathInAssetsDir){
    AssetManager assetManager = AppContext.get().getResources().getAssets();
    InputStream inputStream = null;
    try {
        inputStream = assetManager.open(pathInAssetsDir);
        if(null != inputStream ) {
           return true;
        }
    }  catch(IOException e) {
        e.printStackTrace();
    } finally {
        try {
            inputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }  
    return false;
}

score 6 · Accepted Answer · edited Jan 20 '17 at 10:42

6

Yes and No.

A normal user would not be able to delete them, but a user on a rooted phone who doesn't know what they're doing… that's a different situation.

If you ask me, the extra code is not needed. Also if you try and open a file that doesn't exist, you will get an exception thrown at some point, catch that and display a dialog if you really want to.

edited Jan 20 '17 at 10:42

Tim Kist

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answered Aug 28 '10 at 23:26

smith324

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Great! Thanks Chris. I do have a 'try/catch' deal going on in the code but I wondered about a user being able to access the assets. Hey, try to say, "Access the assets" five times fast. Ha! – Allan Aug 28 '10 at 23:33
1

More than that -- the only way to "delete" them is to rebuild the .apk without them, which requires also resigning it with a different cert. If you crash because someone did this, they more than deserve it. :p – hackbod Aug 29 '10 at 02:32
Not true for bundled apps. An user may not have the folder because the split is optional. – Muntashir Akon Jan 04 '21 at 14:32
This answer is very old. njzk2 already has an answer for this https://stackoverflow.com/a/7337516/6378928 – harveyhans Aug 07 '21 at 01:50

score 2 · Answer 5 · answered Oct 30 '18 at 15:08

AssetManager am = getAssets();

    try {
        List<String> mapList = Arrays.asList(am.list("path/in/assets/folder"));

        if (mapList.contains("file_to_check")) {
            Log.e("ERROR", "exists");
        } else {
            Log.e("ERROR", "not exists");
        }
    } catch ( IOException ex){
        ex.printStackTrace();
    }

Convert to function or method can be easy ;)

score 1 · Answer 6 · answered Aug 28 '10 at 23:30

I think you should be OK. From having a root around in my phone I can't see any way of deleting the assests without deleting the app as it all seems to be wrapped up in the .apk file. You can do it but I think you need to be rooted or use adb.

I would personally surround any reading/writing with a try/catch block anyway, just to be safe.

Check for file existence in androids assets folder?

6 Answers6

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