Android 媒体商店问题：插入新播放列表返回空 URI

Question

I implemented a method for creating playlist in the Media Store using the method below:

public static long createPlaylist(ContentResolver resolver, String name) {
    ContentValues values = new ContentValues(1);
    values.put(MediaStore.Audio.Playlists.NAME, name);
    Uri uri = resolver.insert(MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI, values);
    if (uri == null) {
        throw new Exception(
            "Failed to insert playlist: " + values);
    }

    String idString = uri.getLastPathSegment();
    if (idString == null) {
         throw new Exception(
              "Failed to parse uri last segment: " + uri);
    }

    return Long.parseLong(idString);
}

The method returns an id of newly created playlist. It works perfect on all devices except Nokia 3.1 Android 9. It fails by returning null URI when inserting values in Content resolver.

I also tried to insert values like in the code below:

ContentValues values = new ContentValues(3);
values.put(MediaStore.Audio.Playlists.NAME, name);
values.put(MediaStore.Audio.Playlists.DATE_ADDED, now);
values.put(MediaStore.Audio.Playlists.DATE_MODIFIED, now);

What could be the reason for that? I thought it should be working same way on all devices cause of the common implementation of Media Store in the framework.

Thanks for any help in advance.

Answer 1

Have a look at logcat logs. The method insert logs why it returned null. For instance, I had the same issue and it allowed me to find the cause :

SQLiteDatabase(26594): android.database.sqlite.SQLiteConstraintException: UNIQUE constraint failed: files._data (code 2067 SQLITE_CONSTRAINT_UNIQUE)

So in my case, I was trying to save a file with a name that was already existing.

---

EDIT:

More precisions on my issue:

I was creating a file name "hello.png" with resolver.insert(...) just like you. Normally, if a file with that very name already exists in the file system, the new file is automatically renamed "hello (x).png"

Then for test purpose, I had to delete this file with adb, using adb shell rm -rf <myFolder> . But that was my mistake.

Since Android 10, you must use ContentResolver and Media Store, which is a database keeping track of the files saved by the app. rm -rf does not update this database, so for the file system, no file named hello.png was existing (then the file is not renamed to hello (1).png ). But the database had a record saying that a such a file was existing, hence the exception SQLiteConstraintException .

On Android 10+, to delete a file created by an application , you have to use

adb shell content delete <args>

adb shell content allow you to make SQL like queries to the ContentResolver data base. For instance :

adb shell content query --uri content://media/external/images/media

produces a list of all external images. You can then build the correct query to delete the right file(s).

In my case it was:

adb shell content delete --uri content://media/external/images/media --where bucket_display_name="\'HelloCollection\'"

This command will both remove the entry in the database and delete the file in the file system.

Answer 2

Not sure why you would want a value for uri. My method to insert works without fail, even on android 10. It is basically the same as your example though (although inserting into playlists brings up a file io permission error in Android 10)

    public void createnewPlaylist(Context context, String newplaylist) {
    if (newplaylist != null && context != null) {

        ContentResolver resolver = context.getContentResolver();
        ContentValues values = new ContentValues(1);
        values.put(MediaStore.Audio.Playlists.NAME, newplaylist);
        try {
            resolver.insert(MediaStore.Audio.Playlists.EXTERNAL_CONTENT_URI, values);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}