Question

I have a class:

public class DbAdapter {
    private DbHelper dbHelper;
    private SQLiteDatabase db;
    private final Context context;
    ...
}

and i want have it available in all activities. The class provides access to my sqlite database.

What is the most elegant and neat way to do it? I thought about creating object in each activity (it should “connect” me to the same database, right?).

Answer 1

You can achieve it extending the Application class. Google has this to say about it:

Base class for those who need to
maintain global application state. You
can provide your own implementation by
specifying its name in your
AndroidManifest.xml’s
tag, which will cause that class to be
instantiated for you when the process
for your application/package is
created.

There is normally no need to subclass
Application. In most situation, static
singletons can provide the same
functionality in a more modular way.
If your singleton needs a global
context (for example to register
broadcast receivers), the function to
retrieve it can be given a Context
which internally uses
Context.getApplicationContext() when
first constructing the singleton.

I have done it myself like this:

public class App extends Application {

    private DbHelper dbHelper;

    @Override
    public void onCreate() {
        super.onCreate(); 
        dbHelper = new DbHelper(this);

    }

    public SQLiteDatabase getDatabase(){
        return dbHelper.getWritableDatabase();
    }

    @Override
    public void onTerminate() {
        super.onTerminate();
        dbHelper.close();
    }   
}

Then you just access it calling getApplicationContext.getDatabase()