Android save downloaded data to SD

Question

I've developed an app which - download some data ( .png and .wav files ) - insert the path where each files is downloaded into a database (SQLite)

So far so good, everything works. Some users asked me if there was a way to move the the downloaded data in the sd card in order to save some internal space.

By now i create the directory with this line of code

File directory = getApplicationContext().getDir("folderName", Context.MODE_PRIVATE);

Then the app will fill it with all the stuff I downloaded.

I tried using this piece of code:

                try {
                File newFolder = new File(Environment.getExternalStorageDirectory(), "TestFolder");
                if (!newFolder.exists()) {
                    newFolder.mkdir();
                }
                try {
                    File file = new File(newFolder, "MyTest" + ".txt");
                    file.createNewFile();
                    System.out.println("Path: " + file.getPath());
                } catch (Exception ex) {
                    System.out.println("ex: " + ex);
                }
            } catch (Exception e) {
                System.out.println("e: " + e);
            }

And this create a folder and a text file into: /storage/emulated/0/TestFolder/MyTest.txt Which is not my sdcard directory, it should be: /storage/sdcard1/TestFolder/MyTest.txt

So my question is: - where and how I saved my app's private data (.png and .wav files) in the SD card?

Answer 1

The getExternalFilesDir, getExternalStorageDirectory or relatives, does not always return a folder on a SD card. On my Samsung for example, it returns an emulated, internal SD card.

You can get all external storage devices (also the removable) using ContextCompat.getExternalFilesDirs.

My next step, is to use the folder on the device with the largest free space. To get that, I enumerate the getExternalFilesDirs, and call getUsableSpace on every folder.

I use this code to store (cache) bitmaps in a folder named "bmp" on the device.

    @SuppressWarnings("ResultOfMethodCallIgnored")
    private static File[] allCacheFolders(Context context) {
        File local = context.getCacheDir();
        File[] extern = ContextCompat.getExternalCacheDirs(context);

        List<File> result = new ArrayList<>(extern.length + 1);

        File localFile = new File(local, "bmp");
        localFile.mkdirs();
        result.add(localFile);

        for (File anExtern : extern) {
            if (anExtern == null) {
                continue;
            }
            try {
                File externFile = new File(anExtern, "bmp");
                externFile.mkdirs();
                result.add(externFile);
            } catch (Exception e) {
                e.printStackTrace();
                // Probably read-only device, not good for cache -> ignore
            }
        }
        return result.toArray(new File[result.size()]);
    }



    private static File _cachedCacheFolderWithMaxFreeSpace;
    private static File getCacheFolderWithMaxFreeSpace(Context context) {
        if (_cachedCacheFolderWithMaxFreeSpace != null) {
            return _cachedCacheFolderWithMaxFreeSpace;
        }
        File result = null;
        long free = 0;
        for (File folder : allCacheFolders(context)) {
            if (!folder.canWrite()) {
                continue;
            }
            long currentFree = folder.getUsableSpace();
            if (currentFree < free) {
                continue;
            }
            free = currentFree;
            result = folder;
        }
        _cachedCacheFolderWithMaxFreeSpace = result;
        return result;
    }

Answer 2

try this

File sdCard = Environment.getExternalStorageDirectory();
File dir = new File (sdCard.getAbsolutePath() + "/newfolder");
dir.mkdirs();

add permission in Manifest file

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />