The opposite attention-grabbing factor concerning the NotePadProvider classification is the inner DatabaseHelper category, which extends the SQLiteOpenHelper type. jointly, the 2 sessions look after preliminary- izing the Notepad database, beginning and shutting it, and acting different database projects. curiously, the DatabaseHelper category is simply a couple of traces of customized code (see directory 2-5), whereas the Android implementation of SQLiteOpenHelper does many of the heavy lifting. directory 2-5. The DatabaseHelper classification inner most static type DatabaseHelper extends SQLiteOpenHelper { DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db. execSQL("CREATE desk " + NOTES_TABLE_NAME + " (" + Notes. _ID + " INTEGER basic KEY," + Notes. name + " TEXT," + Notes. word + " TEXT," + Notes. CREATED_DATE + " INTEGER," + Notes. MODIFIED_DATE + " INTEGER" + ");"); } //… } 15967ch02. indd 37 6/5/09 11:18:39 AM 38 bankruptcy 2 ■ GettING YOUr ft rainy As proven in directory 2-5, the onCreate() technique creates the Notepad desk. discover that the class’s calls the superclass’s with the identify of the desk. The superclass will name the onCreate() technique provided that the desk doesn't exist within the database. additionally become aware of that one of many columns within the Notepad desk is the _ID column we mentioned within the part “Dissect- ing the applying. ” Now let’s examine one of many CRUD operations: the insert() approach (see directory 2-6). directory 2-6. The insert() procedure //… SQLiteDatabase db = mOpenHelper. getWritableDatabase(); lengthy rowId = db. insert(NOTES_TABLE_NAME, Notes. notice, values); if (rowId > zero) { Uri noteUri = ContentUris. withAppendedId( NotePad. Notes. CONTENT_URI, rowId); getContext(). getContentResolver(). notifyChange(noteUri, null); go back noteUri; } The insert() approach makes use of its inner DatabaseHelper example to entry the database and then inserts a notes list. The lower back row identification is then appended to the URI and a brand new URI is back to the caller. At this element, you have to be acquainted with how an Android program is laid out. You will be in a position to navigate your approach round Notepad, in addition to a few of the different samples in the Android SDK. try to be capable of run the samples and play with them. Now let’s examine the final lifecycle of an Android software. interpreting the appliance Lifecycle The lifecycle of Android functions differs drastically from the lifecycle of web-based J2EE functions. J2EE apps are loosely controlled by way of the box they run in. for instance, a J2EE box can eliminate an program from reminiscence if it sits idle for a predetermined time interval. But the container generally won’t move applications in and out of memory based on load and/or to be had assets. In different phrases, it’s as much as the applying vendors to make sure that assets can be found. The lifecycle of an Android software, nevertheless, is precisely controlled by means of the sys- tem, in keeping with the user’s wishes, on hand assets, etc.