I've read Android dev guide and notice that we can implement different classes for the content provider. So,
There are many content providers or just one content provider in one Android app?
How to properly implement different content provider classes like that?
Here is what I read from the dev guide:
You implement a provider as one or more classes in an Android
application
http://developer.android.com/guide/topics/providers/content-provider-creating.html
You can implement as many as you want, as you can see from the documentation here. To register a content provider, you need to add its corresponding <provider> tag in the Android Manifest.
In most cases, however, you won't need multiple content providers. One is usually enough, as it can handle multiple tables. You should only really need more than one if you want your app to provide public access to 2+ separate data entities.
You can use (provide as well as use) as many content providers per app as you need. They need different content URIs, of course.
In addition to the uses outlined in the document (your link) you can use content providers for other purposes as accessing data storage. The content URI can have parameters, so you can use a content provider similarly to a web service.
You can create as many content providers as you want. But do you need them al?
What content provider classes do you want to implement? If you read the page very good you should have seen that it contains links to two pages:
http://developer.android.com/guide/topics/providers/content-provider-basics.html - Content Provider Basics
http://developer.android.com/guide/topics/providers/content-provider-creating.html#ContentProvider - Implementing the ContentProvider Class
I suggest you first read those pages. Google is giving some more information about Content Providers, tutorials and examples:
http://android10.org/index.php/articlesdatastorage/252-content-providers-using-and-creating-them
http://thinkandroid.wordpress.com/2010/01/13/writing-your-own-contentprovider/
http://www.vogella.com/articles/AndroidSQLite/article.html
http://about-android.blogspot.com/2010/04/content-provider-example-1.html
There is no rule as such that you have to implement only one content provider per application. If your project demands, then you can do so.
If you want to implement multiple content providers in your application package, then make sure that authorities part of each content provider is unique, to route the incoming data requests to each content providers properly.
But having too many content providers can really confuse you and not required.
The only scenario that I see to have multiple content providers is, if you are having multiple databases in your application and you want to share all those databases with outside applications. Where you can use separate content provider for each database to share it with outside world.
Hope it helps.
Related
I know that browser is content provider but i want to know, is bookmark (which support to browser) is also a content provider.
Be aware in android 6 global bookmarks are removed.
In general, any app can implement its own bookmarks and share it as content provider.
You may ask - but how do clients find provider? Well, it’s required to know the URIs of a provider to access it. The recommendation is to publish public constants for the URIs and document them to other developers.
I need to make an app, similar to Google Now, which would search other apps content that is exposed via Content Providers.
The problem I have, is that all resources I found talk about making your app searchable, but I need the opposite - how to search through all those apps? Is this a private API that only Google Now uses or can I also make such an app?
Currently, I managed to get a list of all searchable apps by reading all meta tags and filtering those with "android.app.searchable" but there must be a better way.
The logical flow should be:
find apps with "android.app.searchable" meta tag
read searchable.xml config to get the content provider
query the content provider from search box
I have two apps and I want one app to change preferences in another app.
Is it possible? If so, then how?
It means that you need some passage between two applications.
If A application provides content provider, B application can access that content provider and change values in that provider.
Have a look this article http://developer.android.com/guide/topics/providers/content-providers.html
You could use Content Providers. Put your settings in a database so that the other application can read.
I have seen custom content providers for sqLite in apps, but thats about it. When should a Custom Content provider be built?
EboMike in this question says:
Other apps will be able to access your data.
You can wrap and abstract a lot of the query logic in your content provider, and limit access.
You will be able to lean on the system to allow for things like managed queries.
Remember that you can control user interacts with your data,for example you can prevent user from modifying data or you can force system to open data with explicit App and so on.
When querying a ContentProvider on Android, one specifies the ContentProvider of interest by providing the "content URI" for that ContentProvider. What happens when multiple ContentProvider's serve that same URI, either intentionally? or maliciously?
When trying to open a pic on my phone, I've seen it prompt with apps that can "handle" the image. Will the same kind of thing happen here?
Multiple ContentProviders can't do this. The first application that registers a content provider using the element in its manifest has control over the URI pattern. I'm pretty sure that you'll get an installation error if you try to add another provider that uses the same URI pattern. Android keeps track of providers and URIs.
When you see a prompt with multiple apps for handling a file or situation, that's because the apps have specified an with a child that includes
android.intent.category.CATEGORY_ALTERNATIVE or android.intent-category.CATEGORY_SELECTED_ALTERNATVE. In essence, the app or apps are declaring themselves to be alternatives to the action specified in the child. This allows the user to have multiple choices for handling a type of data.
It makes sense to provide alternatives: a user might want to edit a picture, share it via Twitter, or e-mail it.
Note that two content providers can do the same thing, but they can't use the same URI. An app has to make a conscious choice of which one to use, or provide some mechanism of choosing between the two.