Managing SQLite Database

Approach #1: Use a Singleton to Instantiate the SQLiteOpenHelper

Declare your database helper as a static instance variable and use the Singleton pattern to guarantee the singleton property. The sample code below should give you a good idea on how to go about designing the DatabaseHelper class correctly.

The static getInstance() method ensures that only one DatabaseHelper will ever exist at any given time. If the sInstance object has not been initialized, one will be created. If one has already been created then it will simply be returned. You should not initialize your helper object using with new DatabaseHelper(context)! Instead, always use DatabaseHelper.getInstance(context), as it guarantees that only one database helper will exist across the entire application’s lifecycle.

public class DatabaseHelper extends SQLiteOpenHelper { 

  private static DatabaseHelper sInstance;

  private static final String DATABASE_NAME = "database_name";
  private static final String DATABASE_TABLE = "table_name";
  private static final int DATABASE_VERSION = 1;

  public static synchronized DatabaseHelper getInstance(Context context) {

    // Use the application context, which will ensure that you
    // don't accidentally leak an Activity's context.
    // See this article for more information: http://bit.ly/6LRzfx
    if (sInstance == null) {
      sInstance = new DatabaseHelper(context.getApplicationContext());
    }
    return sInstance;
  }

  /**
   * Constructor should be private to prevent direct instantiation.
   * make call to static method "getInstance()" instead.
   */
  private DatabaseHelper(Context context) {
    super(context, DATABASE_NAME, null, DATABASE_VERSION);
  }
}

Approach #2: Wrap the SQLiteDatabase in a ContentProvider

This is also a nice approach. For one, the new CursorLoader class requires ContentProviders, so if you want an Activity or Fragment to implement LoaderManager.LoaderCallbacks<Cursor> with aCursorLoader (as discussed in this post), you’ll need to implement a ContentProvider for your application. Further, you don’t need to worry about making a singleton database helper withContentProviders. Simply call getContentResolver() from the Activity and the system will take care of everything for you (in other words, there is no need for designing a Singleton pattern to prevent multiple instances from being created).

转载：http://www.androiddesignpatterns.com/2012/05/correctly-managing-your-sqlite-database.html