观察Android中的应用程序状态更改

Question

I've come to Android from web programming, and in the web, we've got a number of libraries for tracking application state and observing changes:

• Backbone models and collections
• Knockout.js
• Flux/Redux
• RxJS

How do apps track and observe global state in Android? Obviously RxJS has an analog in RxJava, and I've seen some Redux ports, but are those common? If not, what is typical?

Edit : "global state" is ambiguous, and I don't have a good definition, but an example might be a bunch of user profiles fetched from the server. Multiple activities might need that information, and it'd be inefficient if they independently fetched it, so it's best to have a single store for them in the application.

Answer 1

There are a lot of ways to communicate between layers.

1) You can use event bus approach. Otto or EventBus library. Also, you can implement custom event bus using RxJava.

2) You can use local broadcast receiver.

3) You can use just simple callbacks or observer pattern depending on the number of receivers.

4) You can use RxJava which is quite popular now in Android community.

Answer 2

In addition to what @Anton said, the following are both ways to both observe and query data from anywhere in the application:

1)SQLLite Database Tutorial

2)And the much more robust ContentProvider Google Docs

The SQLLite Database will provide a database for simple storing and retrieving of object data.

The ContentProvider allows you to leverage Android's built in services for storing and retrieving data. If you want your data to be accessible by other applications, a ContentProvider allows you to make it available. So in a sense, you data would then become "global" to any application that wants to incorporate it.

EDIT

In my experience, I wouldn't use them unless I absolutely needed to be able to query larger sets of data. They are a bit cumbersome.

For example, a big disadvantage of the SQLLite Database is you have to write ALL of your CRUD operations. To help alleviate that, there are some ORM frameworks that are available that can make it simpler to use standard CRUD functions with any tables you make in the database. If you do decide to go that route, here are five that are apparently recommended 5 recommended Android ORMs

Another route that may be viable depending on what you are looking to do, is to use an API service like Parse to house and query your data. Parse is open source now, and so you'll need to set it up on your own server, but it gives you the power of all of their built in querying. (Note: the database is MongoDB).

In short, getting the extra power to query takes some effort in Android but it is possible, and there are some viable solutions out there to help alleviate the burden.