ソフトウェアエンジニアの技術ブログ：Software engineer tech blog

<red lines>
	<!-- Empty view for the list -->
	<RelativeLayout
		android:id="@+id/empty_view"
		android:layout_width="wrap_content"
		android:layout_height="wrap_content"
		android:layout_centerInParent="true">

		<ImageView
			android:id="@+id/empty_shelter_image"
			android:layout_width="wrap_content"
			android:layout_height="wrap_content"
			android:layout_centerHorizontal="true"
			android:src="@drawable/ic_empty_shelter" />

		<TextView
			android:id="@+id/empty_title_text"
			android:layout_width="wrap_content"
			android:layout_height="wrap_content"
			android:layout_below="@+id/empty_shelter_image"
			android:layout_centerHorizontal="true"
			android:fontFamily="sans-serif-medium"
			android:paddingTop="16dp"
			android:text="@string/empty_view_title_text"
			android:textAppearance="?android:textAppearanceMedium" />

		<TextView
			android:id="@+id/empty_subtitle_text"
			android:layout_width="wrap_content"
			android:layout_height="wrap_content"
			android:layout_below="@+id/empty_title_text"
			android:layout_centerHorizontal="true"
			android:fontFamily="sans-serif"
			android:paddingTop="8dp"
			android:text="@string/empty_view_subtitle_text"
			android:textAppearance="?android:textAppearanceSmall"
			android:textColor="#A2AAB0">
	</RelativeLayout>

Using a CursorLoader
Activity -> LoaderCallbacks -> onCreate() ->getLoaderManager().initLoader()->onCreateLoader() -> onLoadFinished() swapCursor(cursor -> onLoaderReset() swapCursor(null)

ArrayAdapter
Data source: ArrayList of words
Data source: Cursor of pets

public class PetCursorAdapter extends CursorAdapter {

	public PetCursorAdapter(Context context, Cursor c){
		super(context, c, 0);
	}

	public view newView(Context context, Cursor c, ViewGroup parent){
		// create and return new blank list item
	}

	public void bindView(View view, Context context, Cursor c){
		// Populate list item view with pet data
	}
}

public class PetProvider extends ContentProvider {

	...

	@Override
	public int update(Uri uri, ContentValues contentValues, String selection,
		String[] selectionArgs){
		final int match = sUriMatcher.match(uri);
		switch (match){
			case PETS:
				return updatePet(uri, contentValues, selection, selectionArgs);
			case PET_ID:
				selection = PetEntry._ID + "=?";
				selectionArgs = new String[] { String.valueOf(ContentUris.parseId(uri))};
				return updatePet(uri, contentValues, selection, selectionArgs);
			default:
				throw new IllegalArgumentException("Update is not supported for " + uri);
		}
	}
}

public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
		String sortOrder){
	SQLiteDatabase database = mDbHelper.getReadableDatabase();

	Cursor cursor;

	int match = sUriMatcher.match(uri);
	switch(match){
		case PETS:
			// 
			break;
		case PET_ID:
			selection = PetEntry._ID + "=?";
			selectionArgs = new String[] { String.valueOf(ContentUris.parseId(uri))};
			cursor = database.query(PetEntry.TABLE_NAME, projection, selection, selectionArgs,
				null, null, sortOrder);
			break;
		default:
			throw new IllegalArgumentException("Cannot query unknown URI " + uri);
	}
	return cursor;
}

public class PetProvider extends ContentProvider {

	@Override
	public Uri insert(Uri uri, ContentValues contentValues){
		final int match = sUriMatcher.match(uri);
		switch (match){
			case PETS:
				return insertPet(uri, contentValues);
			default:
				throw new IllegalArgumentException("Insertion is not supported for " + uri);
		}
	}

	private Uri insertPet(Uri uri, ContentValues values){
		return ContentUris.withAppendedId(uri, id):
	}
}

private Uri insertPet(Uri uri, ContentValues values){
	String name = values.getAsString(PetEntry.COLUMN_PET_NAME);
	if (name == null){
		throw new IllegalArgumentException("Pet requires a name");
	}

	SQLiteDatabase database = mDbHelper.getWritableDatabse();

	long id = database.insert(PetEntry.TABLE_NAME, null, values);
	if (id == -1){
		Log.e(LOG_TAG, "Failed to insert row for " + uri);
		return null;
	}

	return ContentUris.withAppendedId(uri, id);
}

UI Code is directory interacting with database

CatalogActivity ->
EditorActivity -> Content Provider -> PetDbHelper (Pet with ID 1 has weight 7)

Manage access to a structured set of data
-good abstraction layer between data source & UI code (can add data validation, can modify how data is stored UI code is unaffeted)
-work well with other Android framework classes

UI code
Catalog Activity, Content Resolver, Pet Provider, PetDbHelper SQLiteDatabase

Contacts provider
content://com.android.contacts/contacts
Calendar provider
content://com.android.calendar/events
User Dictionary provider
content://user_dictionary/words

Scheme, Content Authority, Type of data

content authority

<provider
	android:name=".data.PetProvider"
	android:authorities="com.example.android.pets"
	android:exported="false" />

int match = sUriMatcher.match(uri);
if (match == CONTACTS){
	// Act on the contacts table
} else if (match == CONTACTS_ID){
	// Act on a single contact in contacts table
}

public class PetProvider extends ContentProvider {

	private static final int PETS = 100;
	private static final int PET_ID = 101;

	private static final UriMatcher sUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
	static {
		sUriMatcher.addURI(PetContract.CONTENT_AUTHORITY, PetContract.PATH_PETS,PETS);
		sUriMatcher.addURI(PetContract.CONTENT_AUTHORITY,PetContract.PATH_PETS + ""/, PETS_ID);
	}
	...
}