Specifying limit / offset for ContentProvider queries

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囚心锁ツ
囚心锁ツ 2020-12-08 03:45

I\'m trying to get my ContentResolver to run this query:

select * from myTable limit 1 offset 2

The only query method in

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  •  暖寄归人
    2020-12-08 04:06

    If you are providing your content provider, then you can use android.net.Uri.Builder#appendQueryParameter for providing limit and offset as query parameters, which the content provider can use while building the query.

    public class MyProvider extends ContentProvider {
        public static final String QUERY_PARAMETER_LIMIT = "limit";
        public static final String QUERY_PARAMETER_OFFSET = "offset";
    
        public Cursor query(Uri uri, ...) {
            String limit = uri.getQueryParameter(QUERY_PARAMETER_LIMIT);
            String offset = uri.getQueryParameter(QUERY_PARAMETER_OFFSET);
    
            SQLiteQueryBuilder builder = new SQLiteQueryBuilder();
    
            // set the table name,...
    
            // leaving handling of null conditions as an exercise to the reader.
            String limitString = offset + "," + limit;
    
            Cursor c = qb.query(db, projection, selection, selectionArgs, null, null, sortOrder, limitString);
    
            //...
    
            return c;
        }
    }
    

    while building the query:

    private static final Uri CONTENT_URI = MyProvider.CONTENT_URI.buildUpon()
            .appendQueryParameter(MyProvider.QUERY_PARAMETER_LIMIT,
                        String.valueOf(limit))
            .appendQueryParameter(MyProvider.QUERY_PARAMETER_OFFSET,
                        String.valueOf(offset))
            .build();
    

    note that the android.net.Uri.Builder#appendQueryParameter encodes the value to prevent sql injection.

    References:

    1. http://laviefrugale.blogspot.com/2012/01/using-limit-with-android-contentprovider.html
    2. http://www.sqlite.org/lang_select.html
    3. https://stackoverflow.com/a/12476458/1523910 + @eocanha's answer

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