将媒体文件保存在 android

Question

I just started with android development and I am very confused about how to save media files to a custom folder in external storage. I have read about scoped storage, Mediastore and I still don't get it.

I'm trying to save files to my own folder in the external storage (just like the Whatsapp folder in external storage). I want the structure to be as so:

(EXTERNAL STORAGE ROOT)
 |--- (RandomFolder)
 |--- (Whatsapp)
 |--- (MyFolder)
        |---(Images)
        |---(Videos)
 |--- ...

I do not want the media files to be stored in default media directories (such as Pictures/ or DCIM/). I have some questions:

1. Which one to use? Scoped storage or Mediastore API?
2. How to implement the above?

Additional Information:

1. I want the files to remain even when the app is uninstalled
2. My app targets Android 10 (API 29), but minSdkVersion is Android 8.0 (API 26)
3. I will be using OutputStream to save my files.

So which method should I take?

Answer 1

You can save an image and other media files to external storage, however, in order for those files to show up in the other apps, like the Gallery app, you need to register them in the MediaStore. How are you saving the files? Are you creating the files from scratch or are you simply copying them from another directory?

Here is an example of how to save a Bitmap object (jpg or png) to external storage and register it in the MediaStore. First any existing records of the file are deleted from the MediaStore and then the Bitmap is saved to external storage using the ContentResolver.insert() method.

Note that the DATA column in the MediaStore refers to the file's full path.

import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.Context;
import android.graphics.Bitmap;
import android.net.Uri;
import android.provider.MediaStore;
import java.io.File;
import java.io.OutputStream;
import java.util.ArrayList;
import java.util.Objects;

public class SaveImageToMediaStore
{
    public static boolean saveImage(
            Context context, Bitmap bitmap,
            int jpgQuality, int pngQuality, String fileFullPath)
    {
        try
        {
            deleteFileFromMediaStore(context, fileFullPath);

            saveImageAndInsertIntoMediaStore(context, fileFullPath, bitmap, jpgQuality, pngQuality);

            return true;
        }
        catch (Exception ex) { return false; }
    }

    public static boolean saveImageAndInsertIntoMediaStore(
            Context context, String fileFullPath,
            Bitmap bitmap, int jpgQuality, int pngQuality)
    {
        try
        {
            Bitmap.CompressFormat format;
            int quality;
            String mimeType;

            if (fileFullPath.toLowerCase().endsWith(".jpg") ||
                    fileFullPath.toLowerCase().endsWith(".jpeg"))
            {
                format = Bitmap.CompressFormat.JPEG;
                quality = jpgQuality;
                mimeType = "image/jpg";
            }
            else if (fileFullPath.toLowerCase().endsWith(".png"))
            {
                format = Bitmap.CompressFormat.PNG;
                quality = pngQuality;
                mimeType = "image/png";
            }
            else
            {
                return false;
            }

            ContentValues contentValues = new ContentValues();
            contentValues.put(MediaStore.MediaColumns.DISPLAY_NAME, getShortName(fileFullPath));
            contentValues.put(MediaStore.MediaColumns.MIME_TYPE, mimeType);
            contentValues.put(MediaStore.MediaColumns.DATA, fileFullPath);

            ContentResolver resolver = context.getContentResolver();
            Uri uri = resolver.insert(MediaStore.Images.Media.EXTERNAL_CONTENT_URI, contentValues);
            OutputStream out = resolver.openOutputStream(Objects.requireNonNull(uri));
            bitmap.compress(format, quality, out);
            Objects.requireNonNull(out).close();

            return true;
        }
        catch (Exception ex) { return false; }
    }

    public static boolean deleteFileFromMediaStore(
            Context context, String fileFullPath)
    {
        File file = new File(fileFullPath);

        String absolutePath, canonicalPath;
        try { absolutePath = file.getAbsolutePath(); }
        catch (Exception ex) { absolutePath = null; }
        try { canonicalPath = file.getCanonicalPath(); }
        catch (Exception ex) { canonicalPath = null; }

        ArrayList<String> paths = new ArrayList<>();

        if (absolutePath != null) paths.add(absolutePath);
        if (canonicalPath != null && !canonicalPath.equalsIgnoreCase(absolutePath))
            paths.add(canonicalPath);

        if (paths.size() == 0) return false;

        ContentResolver resolver = context.getContentResolver();
        Uri uri = MediaStore.Files.getContentUri("external");

        boolean deleted = false;

        for (String path : paths)
        {
            int result = resolver.delete(uri,
                    MediaStore.Files.FileColumns.DATA + "=?",
                    new String[] { path });

            if (result != 0) deleted = true;
        }

        return deleted;
    }

    public static String getShortName(String path)
    {
        if (path.endsWith("/")) path = path.substring(0, path.length() - 1);

        int pos = path.lastIndexOf('/');

        if (pos == -1) return path;

        return path.substring(pos + 1);
    }

}