Is it possible to create a custom ContentProvider to
Access android existing database (e.g. Contacts, SMS)?
Extend an Exciting ContentProvider which has access to android existing database (e.g. ContactsProvider to access Contacts DB)?
Thank you.
Short Answer: Yes
Longer answer:
ContentProviders are a layer sitting in between the "outside world" (e.g. other Android Activities) and the back-end data storage. You will never have direct access to the database. The database is stored in the Activities private storage space. So all you can do is dictated by the ContentProvider you are addressing.
If the ContentProvider only allows read-only access to the data, than that is all you can do.
So in the end, you can only offer access which has at most the kind of access as the ContentProvider you are using. You can however expose a different data structure. Or you could also create one ContentProvider which uses multiple other providers internally.
On the bottom line, within the given bounds, your imagination is the limit.
Related
i'm beginner in android development, need help regarding ContentProvider.
public class My Application extends ContentProvider {}
A ContentProvider manages access to a structured set of data. It encapsulates the data and provide mechanisms for defining data security. ContentProvider is the standard interface that connects data in one process with code running in another process.
Kindly refer following links,
https://developer.android.com/guide/topics/providers/content-provider-creating.html
and
https://www.tutorialspoint.com/android/android_content_providers.htm
A content provider component supplies data from one application to others on request. one application cannot directly access (read/write) other application's data. Every application has its own id data directory and own protected memory area.
Content provider is the best way to share data across applications. Content provider is a set of data wrapped up in a custom API to read and write. Applications/Processes have to register themselves as a provider of data.
In simple language you can say content provider is a shared database which expose his properties and on there behalf of them other application can access and store the data as per the implementation privilege
Content providers can help an application manage access to data stored by itself, stored by other apps, and provide a way to share data with other apps. They encapsulate the data, and provide mechanisms for defining data security. Content providers are the standard interface that connects data in one process with code running in another process. Implementing a content provider has many advantages. Most importantly you can configure a content provider to allow other applications to securely access and modify your app data.
It is not that they are used only to share data with other applications. You may still use them because they provide a nice abstraction, but you don’t have to necessarily share data with other apps. This abstraction allows you to make modifications to your application data storage implementation without affecting other existing applications that rely on access to your data
You can get more info from the documentation.
ContentProvider is mainly used for access data from one application to another application.
For example by using ContentProvider we can get phone contacts,call log from phone to our own application in android.we can also access data which are stored in (sqlite)databases.
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?
I was wondering whether we can use the databases like (contacts.db, mmssms.db) directly instead of content providers ?
I have a reason to ask so. In my recent project, I was supposed develop a contact app. I used content provider for contact management. As I have learnt via content providers, I can query only table at a time via URIs, there is no way (at least, I didn't find) to join two tables and then get a query resolved.
And I had read, that databases are only visible to the applications that originally created them, so do my app would be able to access these databases ?
I am just a hobby developer for my own phone. I have no intention to make an app that directly uses the databases. I can pull the database from device, analyse them via sqlite. It is not that I am up against the content providers or they don't suit my need write now, it is just that it can be done or not ?
Any opinions ?
Content Providers give you a lot more than just database access. Being able to use Loaders to automatically reload your data (and update your UI) when the underlying data changes can vastly simplify your applications.
The goal of Content Providers is more to create a single, controlled layer for accessing your data. There is nothing stopping you from creating a custom URI that joins multiple tables together and returns the resulting joined result.
If we want to share our data with other Android applications,
(1) we may create a SQlite database and make it accessible by other applications or
(2) create a ContentProvider.
What are the basic differences in the above mentioned two approaches?
ContentProvider is exposing data to other application, a non-content provider database is only accessible by that application.
I am writing a small featurecontrol-application, which has several feature settings stored and managed. All applications use my featurecontrol-application to retrieve settings like whether feature-x is enabled or not or what is feature-x-value . Can I use contentprovider for this or are there any other alternatives?
If you have several applications, and they have to share same data (content) usage of ContentProvider looks to me as quite good and logical solution.
Content provider is one option to implement communication between different applications. But it does not need DB as a backbone. Instead of DB you can use table of constants. To create ContentProvider you just need to override several functions, no constraint is imposed to use DB.
Another option is to implement IPC via AIDL. That also gives you interface to share objects, but IMO since you just need to share constants ContentProvider is easier and faster solution.