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Multiple ContentProvider in a single app

Is it ok to create ContentProvider for each table means multiple content provider in a single app ?
I want to do that for various reasons.
1- As my app grows the single ContentProvider class become bloated and messy.
2- I don't want to share whole ContentProvider class with another app. I just want to share few or only one table.

In general you can have multiple content providers in one app, so that's not a problem at all. Just make sure that both content providers have different authorities, otherwise it won't work. Content provider authorities have to be unique.
However, there are more things to consider when deciding whether to go with one or multiple content providers. Here are some of them:
Your question kind of implies that you plan to share the same SQLite database (I've figured that from the term "table") in both content providers, which is not a good idea. Every content provider would probably have its own instance of the SQLiteOpenHelper for the database which means you may run into locking issues, see this answer: https://stackoverflow.com/a/3689883/1558654
You probably can find a way to share the same SQLiteOpenHelper instance with both content providers, but that would most likely result in a bad architecture and a probably other issues in the long run.
So if you want to use multiple content providers, make sure both content providers have their own dedicated authorities and databases, which also means that you can't use certain database features like foreign key constraints (or you'll have to take care of that on your own) or transactions (if they would span both databases).
Regarding your reason #1: Not sure if you're talking about the interface (the contract) or about the actual .java file, but that doesn't really matter, since it's merely an architectural problem that's definitely solvable when having a single content provider. If your content provider class file is too large your architecture is probably not so good.
Also the decision whether you should use two content providers or not depends a lot on what kind of data they provide.
Is the data related (or is it about the same kind of data)? It's probably better to use just one content provider.
It's completely unrelated? Two content providers are probably the better choice.
Reason #2 needs more consideration. The question is why don't you want to expose certain tables? Is it a security / privacy issue? Or is it just that other apps won't need the data?
If it's for security or privacy, it's probably better to use two content providers and set android:exported="false" on the one holding the sensitive data. But even with one content provider there are ways to protect these.
If security or privacy are not an issue, just don't publish the content URIs to the other tables in your public contract.

Yes, that is fine. As you point out it allows each one to contain specific pieces of data and each one can have the appropriate permissions.

Where do application logic and constraints go when creating ContentProviders?

I'm starting to learn Android development, and also have been trying to follow the DDD design patterns. One thing that has me confused is where application logic goes with respect to ContentProviders.
ContentProviders look a lot like repositories to me, but a lot of times I don't want to expose my repositories directly. There may be some additional application logic inside a Service which the repositories/database.
Most of the examples of ContentProviders I find show them accessing the database directly. Is it wrong to have a Service or Application object in between the ContentProviders and database?
For example I'm trying to create a personal finance/budget app (e.g Mint/Quicken etc..). I'm going to have a database of transactions and a corresponding TransactionProvider. In most cases transactions are independent from one another. Yet if two transactions are marked as part of the same "Transfer" there there will be some fields that I will want to keep in sync between the two transactions. If someone changes the category or amount of one transaction, I want to make sure the same values are updated for the transaction for the other account of the transfer.

A ContentProvider can execute arbitrary code on its insert(), update(), delete() and query() methods. They are not necessarily mapped one-to-one with the corresponding database operations, and neither do the structure definitions (i.e. fields) themselves. You could, for example:
Update more than one table when you insert, update or delete.
Keep normalized tables in SQLite, but present a non-normalized interface for querying.
Not store data in a database at all (for example to expose/manipulate the files available in your application's private storage).
&c.
So you can, indeed, include whatever business logic you want in the "backend" of the ContentProvider. In your case that would mean updating associated records to keep them in sync.
Just to clarify, since you're starting Android development, it's not necessary to build a ContentProvider if you just want to store data in SQLite -- you can use SQLiteDatabase directly for that. A ContentProvider is generally to expose your own data to other applications, or for specialized cases such as search suggestions.
From Creating a Content Provider:
Decide if you need a content provider. You need to build a content
provider if you want to provide one or more of the following features:
You want to offer complex data or files to other applications.
You want to allow users to copy complex data from your app into other apps.
You want to provide custom search suggestions using the search framework.
You don't need a provider to use an SQLite database if the use is
entirely within your own application.
If you're building a financial data app, you probably don't need one. Do you want other applications to be able to access that data?

Android: What is better, using a SQLiteCursorLoader or implementing a ContentProvider?

I have to show the contents of a SQLite database in a ListView, and seeking the web I have found 2 options:
Using SQLiteCursorLoader, or
Implementing a Content Provider like here
Android Dev docs say a content provider is not needed to access a database, and it should be use to share data with other apps (what I do not need). What do you think is better in terms of efficiency, error-prone and simplicity?
Thank you guys!

Obviously sharing data is the most frequent reason people put for using a content provider.
There have been some bugs in sqlite and multiple users, although not absolute usually a content provider is in a single thread and can solve this issue and yes this is when your sharing data between apps.
A content provider can give you a level of abstraction and possibly have less code maintenance, especially with internal database structure changes.
It allows you to perform asynchronous queries with a CursorLoader, off loading your UI Activities, which is the design recommendation.
In conjunction with a database helper, it makes it easier to get your table and column names correct and narrows down where you have to look and maintain code.
The use of a database helper or contract between your application and content provider can provide some security, as you provide the methods to your and any other application on how the data get updated.
This can also give you some better data integrity, dependent on how complex your database structure is. It leaves the guess work out of was I supposed to update Table A first and then Table B or the other way around.
It can help with table joins and views so you only have to figure that out once and represent them as a URI.
You can created a URI to handle a raw query inside of a content provider to supply results, that otherwise might have been hard to write with the normal URI structure as it's presented in most tutorials. This is also useful if you have to write a correlated query.

When to use a Content Provider

I understand that Content Providers are made to allow publicly sharing data between applications. However, I'm wondering if anyone has thoughts about making a Content Provider to use just within your own app. Would there be any advantages to doing this? Any disadvantages?
In the past I've just implemented the SQliteOpenHelper to access data from my database, but I'm considering creating a Content Provider. I feel like the URI approach to requesting data is clear and concise. On the other hand, will using a Content Provider just for my application be redundant ( since within it I will have a SQliteOpenHelper class ) and more work than I need?

I would argue it is definitely a good idea to use a ContentProvider even if you don't intend to make it public.
It's good practice to provide the extra level of abstraction over your data to make it easier to change internally. What if you decide to change the underlying database structure at a later time? If you use a ContentProvider you can contain all the structural changes within it, where as if you don't use one, you are forced to change all areas of the code that are affected by the structural changes. Besides, it's nice to be able to re-use the same standard API for accessing data rather than littering your code with low-level access to the database.
Also, there is always the chance that you might want to expose your data in the future. If you don't use a ContentProvider up front, it will be much harder to retrofit it in at a later date.
Then, there's the other parts of the Android where ContentProvider's are required/recommended such as when using SyncAdapters and if you want an App Widget that involves data access for instance.
In summary, there is very little overhead involved in writing a ContentProvider up front (once you have learned the API which is a good idea anyway) so it makes sense to do so, even for private data.

If you are not planning to share data, don't think about Content Providers. They are powerful but hard to write and it will be just silly to implement them if you are going to use them internally.
However, I'm wondering if anyone has thoughts about making a Content Provider to use just within your own app.
Of course... for instance, for an old TODO list app I wrote, I had to write a content provider to allow other apps retrieve and access the tasks states. It was part of the requirements, but more than that it made sense and made the app nicer.

Take a look at the MOTODEV Studio for Eclipse. It is a development environment that extends Eclipse. They have a tool where you can automatically generate a content provider for a database. If a content provider makes it easier to access your data and it doesn't have a significant impact on performance go ahead and use it. In most scenarios this will be the case.

In short,Content Providers helps in managing your data effectively. I would suggest to use them for the following reasons.
It acts as an abstraction layer between your UI and database. You can implement data validation in ContentProviders to validate the data entered by the user. It also lets you to modify the structure of the database without touching the UI and other parts.
They play along nicely with other android framework classes like SyncAdapter. For eg., you can automatically refresh a list, when a value in a database changes using ContentProviders along with CursorLoader. Without ContentProviders you have to implement a lot of functionalities like these on your own.
We can safely expose our private data to other apps. Using ContentProviders will allow us to share our data easily and safely with other apps.
So even if you don't need any of these functionalities now, you might need them in future and its good to go the extra mile and implement them right now.

I agree ContentProviders are a little difficult to grasp but they are definitely helpful, even if you want to use them internally for you own app. The best thing about it is that you can customize the contentproviders for suitable URIs.
Here's a scenario where you may have 5 tables in your database, but you need to join a few of them in certain orders before using them. And make a content URI for each of these joins. You could then each use these URIs as a table :)
I suggest you go ahead with Content Provider, you'll be amazed to see how powerful it is.

In my view point, the content-provider comes with plenty of advantages leave alone just sharing data with other apps. If you need to synchronize with the server using a Sync-Adapter, use google cloud messaging, auto update the UI when the underlying data in the DB changes using Loaders, implement search, use widgets... then the content provider is for you.
I prefer you follow the guideline on because one day you may need to implement some of the above features attached to the content-provider
By the way, you can quickly build you database and CP in less than 5 minutes using content provider generator

As said in documentation:
Creating a Content provider
You don't need a provider to use an SQLite database if the use is
entirely within your own application.
So why bother developing this overhead? You want easier and faster development, right? So one layer of abstraction (SQLiteOpenHelper descendent) is enough.
See Occam's Razor
Do not make an entities without very good reason.

Using a Content Provider can help in an additional level of abstraction - Putting it within your own application make add a significant development time to your project. However if you are using it to share data, application settings or configurations across multiple applications then the Content Provider is your choice.
Watch your security levels and I would recommend using SQLcipher to encrypt data-at-reset (DAR) if your Content Provider is writing to SQLite. (I've used a content provider in a few solutions and provided the ability to take a live "snap shot" of the operational values for debugging and testing.)

Do not use content provider if do not wish to share data with other apps. Use simple sqlitedatabase to perform database operations. Be careful while using content providers for storing confidential data because your confidential information may be accessed by other apps

Exact Difference between "Content-Provider" and "SQLite Database"

i have done SQLite database programming for Android, but i dont know anything about
Content-Provider except this: "As i have referred Android Developer page , Android SDK explained about "Content-provider" as it is used to store and retrieve data."
But then,
What is the exact difference between "Content-Provider" and "SQLite Database"?
Which is best to store data, when ?
Any example or helps !!

I found one major difference, as follows:
Storing your data in a database is one good way to persist your data, but there's a caveat in Android-databases created in Android are visible only to the application that created them. That is to say, a SQLite database created on Android by one application is usable only by that application, not by other applications.
So, if you need to share data between applications, you need to use the content provider model as recommended in Android. This article presents the basics of content providers and how you can implement one.
I found this article at this link
Really nice information provided.

What is the exact difference between
"Content-Provider" and "SQLite
Database"?
ContentProvider is a facade -- an API you can implement that exposes databases to other processes. It can be implemented in a way where the data is stored in a SQLite database, but it does not have to be.
Which is best to store data, when ?
That is impossible to answer in the abstract. Generally speaking, unless something is requiring you to use a ContentProvider, just use a database.

I have made many good apps with thousands of users using them which simply used SQLite methods. But that was a while ago and I had to manually write lots of code which now can easily be taken care of by ContentProvider. Back then I was not in favour of using Content Providers because it seemed to only add complexity in the code.
However for last couple of years, as Android has evolved, I have moved to ContentProvider as it saves time and allows you do to more. I now use it extensively. Once you have a Content Provider class written, your life becomes much easier. With ContentProvider I can much easily deal with Cursor Loaders, Loader Callbacks and Bulk Inserts for which I had to write everything manually in the past and still it didn't work as efficiently. Especially when updating the list view, which is now automatically updated thanks to just one notifychange() method. This means now I don't have to type my own listeners and manually updating the content in list views and adapters. Plus, I don't need to worry about opening and closing of databases or worry about memory leaks. That's all handled by the Content Provider. The only problem which once in a while I face is that that you cannot do some complex queries in ContentProviders. In this case you can still use raw queries and use the old fashioned manual interaction with sqlite.
If you have previously written your own DbAdapter, Helper and Observer, you can safely carry them on to your new apps without spending time to convert everything to ContentProvider. But based on my experience, I would highly recommend to move to ContentProvider. It'll take some time to get used to it, but once you have got experience with it, you'll stay with it.
UPDATE 2017
I have now switched to Realm, a much better way to use databases on any platform. Spend a few hours learning it, and save countless hours in your app development career.

1. Content Providers are not Thread Safe
By default content providers are not thread safe. If you have multiple threads using a content provider you can see many different exceptions being thrown and other data inconsistencies. The easiest way to fix this is to use the synchronized keyword on each of the public methods exposed by the content provider.
In this way only one thread at a time can access these methods.
2. Play nice when doing lots of writes
I have the need in the new Serval Maps application to import data from binary files into the database used internally by the application. In order to do this and play nice with the rest of the application it is best to:
Spawn a new thread to undertake the import so other threads are not adversely impacted, in particularly the thread in charge of updating the UI; and
Pause briefly at the end of the each import to give other threads which need to use the synchronized methods more of a chance.
3. Content providers force you to think laterally sometimes
The way that content providers in Android work is to provide a layer of abstraction between the rest of your code and the underlying database. This is mainly due to the fact, as far as I can tell, that content providers can access data from places other than databases.
This means that you can’t execute raw SQL queries on the underlying database and you need to specify the various components of a SQL query using variables passed to the various methods such as the query method. If you have a task that doesn’t fit into the way that SQL is handled by a content provider you have two options:
Think laterally about the query, maybe you can get the data that you need by alternative queries and accessing the results from the cursor; and
Use a URI for accessing the data normally and a special URI that is matched to a specific query for those tasks that don’t have alternatives.

Content Providers are used when you want to share your data across applications.
If you have a database attached with an application and you want another application to use some data, you can implement a content provider that exposes the data

The main difference is: when your app needs to share information to another apps, use Content-Provider. SQLite only storage data for the app who creates it

I read this answer while looking for same doubt, so thought of sharing it.
it states -
It's good practice to provide the extra level of abstraction over your data to make it easier to change internally. What if you decide to change the underlying database structure at a later time? If you use a ContentProvider you can contain all the structural changes within it, where as if you don't use one, you are forced to change all areas of the code that are affected by the structural changes. Besides, it's nice to be able to re-use the same standard API for accessing data rather than littering your code with low-level access to the database.
So, using a content provider would be a good idea.

Think of advanced Content Management Systems. Each object (page, image, news article, event item, etc.) has a content, an address, user permissions, and ways to interact with it from different parts of the system. Content Providers do that for Android. You can now share files or images you may have stored in your application. You can also create custom sharable objects, like bussiness contacts, editable notes, etc. And specify security and the default application to deal with such object when you open them from any other application.

One difference is that Content Providers have platform support for Content Observers. Your going to need to implement your own Observable pattern for a SQLite database.
How to automatically re-query with LoaderManager
ContentObserver for SQLite?