sqlite - Best practices for exposing multiple tables using content providers in Android

Question

I'm building an app where I have a table for events and a table for venues. I want to be able to grant other applications access to this data. I have a few questions related to best practices for this kind of problem.

1. How should I structure the database classes? I currently have classes for EventsDbAdapter and VenuesDbAdapter, which provide the logic for querying each table, while having a separate DbManager (extends SQLiteOpenHelper) for managing database versions, creating/upgrading databases, giving access to database (getWriteable/ReadeableDatabase). Is this the recommended solution, or would I be better off either consolidating everything to one class (ie. the DbManager) or separation everything and letting each Adapter extends SQLiteOpenHelper?

2. How should I design content providers for multiple tables? Extending the previous question, should I use one Content Provider for the whole app, or should I create separate providers for Events and Venues?

Most examples I find only deal with single table apps, so I would appreciate any pointers here.

Answer 1

It's probably a bit late for you, but others may find this useful.

First you need to create multiple CONTENT_URIs

public static final Uri CONTENT_URI1 = 
    Uri.parse("content://"+ PROVIDER_NAME + "/sampleuri1");
public static final Uri CONTENT_URI2 = 
    Uri.parse("content://"+ PROVIDER_NAME + "/sampleuri2");

Then you expand your URI Matcher

private static final UriMatcher uriMatcher;
static {
    uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    uriMatcher.addURI(PROVIDER_NAME, "sampleuri1", SAMPLE1);
    uriMatcher.addURI(PROVIDER_NAME, "sampleuri1/#", SAMPLE1_ID);      
    uriMatcher.addURI(PROVIDER_NAME, "sampleuri2", SAMPLE2);
    uriMatcher.addURI(PROVIDER_NAME, "sampleuri2/#", SAMPLE2_ID);      
}

Then create your tables

private static final String DATABASE_NAME = "sample.db";
private static final String DATABASE_TABLE1 = "sample1";
private static final String DATABASE_TABLE2 = "sample2";
private static final int DATABASE_VERSION = 1;
private static final String DATABASE_CREATE1 =
    "CREATE TABLE IF NOT EXISTS " + DATABASE_TABLE1 + 
    " (" + _ID1 + " INTEGER PRIMARY KEY AUTOINCREMENT," + 
    "data text, stuff text);";
private static final String DATABASE_CREATE2 =
    "CREATE TABLE IF NOT EXISTS " + DATABASE_TABLE2 + 
    " (" + _ID2 + " INTEGER PRIMARY KEY AUTOINCREMENT," + 
    "data text, stuff text);";

Don't forget to add the second DATABASE_CREATE to onCreate()

You are going to use a switch-case block to determine what table is used. This is my insert code

@Override
public Uri insert(Uri uri, ContentValues values) {
    Uri _uri = null;
    switch (uriMatcher.match(uri)){
    case SAMPLE1:
        long _ID1 = db.insert(DATABASE_TABLE1, "", values);
        //---if added successfully---
        if (_ID1 > 0) {
            _uri = ContentUris.withAppendedId(CONTENT_URI1, _ID1);
            getContext().getContentResolver().notifyChange(_uri, null);    
        }
        break;
    case SAMPLE2:
        long _ID2 = db.insert(DATABASE_TABLE2, "", values);
        //---if added successfully---
        if (_ID2 > 0) {
            _uri = ContentUris.withAppendedId(CONTENT_URI2, _ID2);
            getContext().getContentResolver().notifyChange(_uri, null);    
        }
        break;
    default: throw new SQLException("Failed to insert row into " + uri);
    }
    return _uri;                
}

You will need to devide up the delete, update, getType, etc. Wherever your provider calls for DATABASE_TABLE or CONTENT_URI you will add a case and have DATABASE_TABLE1 or CONTENT_URI1 in one and #2 in the next and so on for as many as you want.