Java tutorial
/* * This file is part of nori. * Copyright (c) 2014-2016 Tomasz Jan Gralczyk <tomg@fastmail.uk> * License: GNU GPLv2 */ package io.github.tjg1.nori.database; import android.content.BroadcastReceiver; import android.content.ContentValues; import android.content.Context; import android.content.Intent; import android.content.IntentFilter; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.support.v4.content.AsyncTaskLoader; import android.support.v4.content.LocalBroadcastManager; import android.util.Pair; import java.util.ArrayList; import java.util.List; import java.util.Locale; import io.github.tjg1.library.norilib.clients.Flickr; import io.github.tjg1.library.norilib.clients.SearchClient; /** Utility class providing access to the SQLite API endpoint settings database. */ public class APISettingsDatabase extends SQLiteOpenHelper { //region Broadcast IDs /** ID of the Broadcast sent when data in the database changes. */ public static final String BROADCAST_UPDATE = "io.github.tjg1.nori.database.APISettingsDatabase.update"; //endregion //region SQLite Constants /** Filename of the underlying SQLite database. */ private static final String DATABASE_NAME = "api_settings.db"; /** API Settings table name. */ private static final String TABLE_NAME = "api_settings"; /** Unique ID (primary key) column. */ private static final String COLUMN_ID = "_id"; /** Human-readable endpoint name column. */ private static final String COLUMN_NAME = "name"; /** API Type ID column. */ private static final String COLUMN_TYPE = "type"; /** API endpoint URL column. */ private static final String COLUMN_ENDPOINT_URL = "endpoint_url"; /** Username column. */ private static final String COLUMN_USERNAME = "username"; /** Password/API key column. */ private static final String COLUMN_PASSPHRASE = "passphrase"; /** Database schema version. */ private static final int SCHEMA_VERSION = 1; //endregion //region Instance fields (Context) /** Android context. */ private final Context context; //endregion //region Constructors /** * Create a new API Settings Database access helper. * * @param context Android context. */ public APISettingsDatabase(Context context) { super(context, DATABASE_NAME, null, SCHEMA_VERSION); this.context = context; } //endregion //region SQLiteOpenHelper methods @Override public void onCreate(SQLiteDatabase db) { // SQL query used to create the database schema. String createSQL = String.format(Locale.US, "CREATE TABLE %s (%s INTEGER PRIMARY KEY AUTOINCREMENT, %s TEXT NOT NULL, %s INTEGER NOT NULL, %s TEXT NOT NULL, %s TEXT, %s TEXT);", TABLE_NAME, COLUMN_ID, COLUMN_NAME, COLUMN_TYPE, COLUMN_ENDPOINT_URL, COLUMN_USERNAME, COLUMN_PASSPHRASE); db.execSQL(createSQL); // SQL query used to populate the database with initial data (when the app is first launched). String populateSQL = String.format(Locale.US, "INSERT INTO %s (%s, %s, %s) VALUES ('%s', %d, '%s');", TABLE_NAME, COLUMN_NAME, COLUMN_TYPE, COLUMN_ENDPOINT_URL, "Flickr", SearchClient.Settings.APIType.FLICKR.ordinal(), Flickr.FLICKR_API_ENDPOINT); db.execSQL(populateSQL); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // Do nothing. } //endregion //region Static methods: (De)-Serialization of SearchClient.Settings /** * Serialize a {@link SearchClient.Settings} object into a {@link ContentValues} object used by * Android's SQLite API. * * @param settings Settings object. * @return Serialized {@link ContentValues} object. */ private static ContentValues searchClientSettingsToContentValues(SearchClient.Settings settings) { final ContentValues contentValues = new ContentValues(); contentValues.put(COLUMN_TYPE, settings.getApiType().ordinal()); contentValues.put(COLUMN_NAME, settings.getName()); contentValues.put(COLUMN_ENDPOINT_URL, settings.getEndpoint()); contentValues.put(COLUMN_USERNAME, settings.getUsername()); contentValues.put(COLUMN_PASSPHRASE, settings.getPassword()); return contentValues; } /** * Convert data from a database cursor to a {@link SearchClient.Settings} object. * * @param c Cursor. * @return {@link SearchClient.Settings} object. */ private static SearchClient.Settings cursorToSearchClientSettings(Cursor c) { return new SearchClient.Settings( SearchClient.Settings.APIType.values()[c.getInt(c.getColumnIndex(COLUMN_TYPE))], c.getString(c.getColumnIndex(COLUMN_NAME)), c.getString(c.getColumnIndex(COLUMN_ENDPOINT_URL)), c.getString(c.getColumnIndex(COLUMN_USERNAME)), c.getString(c.getColumnIndex(COLUMN_PASSPHRASE))); } //endregion //region CRUD methods /** * Get single instance of {@link SearchClient.Settings} from the database. * * @param id Row ID. * @return Search client settings object. Null if given ID does not exist in the database. */ public SearchClient.Settings get(long id) { // Query the database. SQLiteDatabase db = getReadableDatabase(); Cursor c = db.query(TABLE_NAME, null, COLUMN_ID + " = ?", new String[] { Long.toString(id) }, null, null, COLUMN_ID, "1"); // Prepare return value. final SearchClient.Settings settings = (!c.moveToNext()) ? null : cursorToSearchClientSettings(c); // Clean up native resources. c.close(); db.close(); return settings; } /** * Get all {@link SearchClient.Settings} objects from the database. * * @return List of pairs mapping database IDs to {@link SearchClient.Settings} objects. */ public List<Pair<Integer, SearchClient.Settings>> getAll() { // Query the database. SQLiteDatabase db = getReadableDatabase(); Cursor c = db.query(TABLE_NAME, null, null, null, null, null, COLUMN_ID); // Convert database Cursor to List. final List<Pair<Integer, SearchClient.Settings>> settingsList = new ArrayList<>(c.getCount()); while (c.moveToNext()) { settingsList.add(new Pair<>(c.getInt(c.getColumnIndex(COLUMN_ID)), cursorToSearchClientSettings(c))); } // Clean up native resources. c.close(); db.close(); return settingsList; } /** * Insert a new {@link SearchClient.Settings} into the database. * * @param settings Settings object. * @return ID of the newly inserted row. */ public long insert(SearchClient.Settings settings) { // Insert data into the database. SQLiteDatabase db = getWritableDatabase(); final long id = db.insert(TABLE_NAME, null, searchClientSettingsToContentValues(settings)); db.close(); sendUpdateNotification(); return id; } /** * Update an existing {@link SearchClient.Settings} object in the database. * * @param id Row ID. * @param settings Settings object with data to update. * @return Number of rows affected. */ public int update(long id, SearchClient.Settings settings) { // Update data in the database. SQLiteDatabase db = getWritableDatabase(); final int rows = db.update(TABLE_NAME, searchClientSettingsToContentValues(settings), COLUMN_ID + " = ?", new String[] { Long.toString(id) }); db.close(); sendUpdateNotification(); return rows; } /** * Delete a row from the database. * * @param id Row ID. * @return Number of rows affected. */ public int delete(long id) { // Remove row from the database. SQLiteDatabase db = getWritableDatabase(); final int rows = db.delete(TABLE_NAME, COLUMN_ID + " = ?", new String[] { Long.toString(id) }); db.close(); sendUpdateNotification(); return rows; } //endregion //region Update notification broadcasts /** * Notify observers that the data in the database has changed. */ private void sendUpdateNotification() { LocalBroadcastManager.getInstance(context).sendBroadcast(new Intent(BROADCAST_UPDATE)); } //endregion //region Inner classes /** Loader class used to asynchronously offload database access to a background thread. */ public static class Loader extends AsyncTaskLoader<List<Pair<Integer, SearchClient.Settings>>> { /** {@link android.content.BroadcastReceiver} receiving database change notifications. */ private final BroadcastReceiver contentChangedBroadcastReceiver = new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { Loader.this.onContentChanged(); } }; /** Database access helper. */ private APISettingsDatabase db; /** Cached result. */ private List<Pair<Integer, SearchClient.Settings>> settingsList; /** * Create a new loader to asynchronously offloads {@link APISettingsDatabase} access to a background thread. * * @param context Android context. */ public Loader(Context context) { super(context); } @Override protected void onStartLoading() { super.onStartLoading(); // Create database instance. this.db = new APISettingsDatabase(getContext()); // If there is a cached result available, deliver it immediately. if (settingsList != null) { deliverResult(settingsList); } // Register broadcast receiver handling database change notifications. LocalBroadcastManager.getInstance(getContext()).registerReceiver(contentChangedBroadcastReceiver, new IntentFilter(APISettingsDatabase.BROADCAST_UPDATE)); // If the data has changed since the last time it was loaded or is not currently available, start a load. if (takeContentChanged() || settingsList == null) { forceLoad(); } } @Override protected void onReset() { super.onReset(); // Release resources. settingsList = null; db.close(); // Unregister broadcast receiver handling database change notifications. LocalBroadcastManager.getInstance(getContext()).unregisterReceiver(contentChangedBroadcastReceiver); } @Override public List<Pair<Integer, SearchClient.Settings>> loadInBackground() { settingsList = db.getAll(); return settingsList; } } //endregion }