数据库操作总结
public ArrayList getUsers(){DBAdapter dbAdapter=DBAdapter.getDBAdapterInstance(this);try {dbAdapter.createDataBase();} catch (IOException e) {Log.i("*** select ",e.getMessage());} dbAdapter.openDataBase();String query="SELECT * FROM user;";ArrayList> stringList = dbAdapter.selectRecordsFromDBList(query, null);dbAdapter.close();ArrayList usersList = new ArrayList();for (int i = 0; i < stringList.size(); i++) {ArrayList list = stringList.get(i);UserBO user = new UserBO();try {user.id = Integer.parseInt(list.get(0));user.name = list.get(1);user.age = Long.parseLong(list.get(2));} catch (Exception e) {Log.i("***" + Select.class.toString(), e.getMessage());}usersList.add(user);}return usersList;} 插入：DBAdapter dbAdapter = DBAdapter.getDBAdapterInstance(Insert.this);dbAdapter.openDataBase();ContentValues initialValues = new ContentValues();initialValues.put("name", etName.getText().toString());initialValues.put("age", etAge.getText().toString());long n = dbAdapter.insertRecordsInDB("user", null, initialValues);Toast.makeText(Insert.this, "new row inserted with id = " + n, Toast.LENGTH_SHORT).show(); 更新：DBAdapter dbAdapter = DBAdapter.getDBAdapterInstance(Update.this);dbAdapter.openDataBase();ContentValues initialValues = new ContentValues();initialValues.put("name", etName.getText().toString());initialValues.put("age", etAge.getText().toString());String id = etId.getText().toString();String [] strArray = {""+id};long n = dbAdapter.updateRecordsInDB("user", initialValues, "id=?", strArray);Toast.makeText(Update.this, n+" rows updated", Toast.LENGTH_SHORT).show(); 删除：DBAdapter dbAdapter = DBAdapter.getDBAdapterInstance(Delete.this);dbAdapter.openDataBase();String id = etId.getText().toString();String [] strArray = {""+id};long n = dbAdapter.deleteRecordInDB("user", "id = ?", strArray);Toast.makeText(Delete.this, n+" rows effected", Toast.LENGTH_SHORT).show(); ublic class DBAdapter extends SQLiteOpenHelper {private static String DB_PATH = "";private static final String DB_NAME = "user.sqlite";private SQLiteDatabase myDataBase;private final Context myContext;private static DBAdapter mDBConnection;/** * Constructor * Takes and keeps a reference of the passed context in order to access to the application assets and resources. * @param context */private DBAdapter(Context context) {super(context, DB_NAME, null, 1);this.myContext = context;DB_PATH = "/data/data/"+ context.getApplicationContext().getPackageName()+ "/databases/";// The Android's default system path of your application database is// "/data/data/mypackagename/databases/"}/** * getting Instance * @param context * @return DBAdapter */public static synchronized DBAdapter getDBAdapterInstance(Context context) {if (mDBConnection == null) {mDBConnection = new DBAdapter(context);}return mDBConnection;}/** * Creates an empty database on the system and rewrites it with your own database. **/public void createDataBase() throws IOException {boolean dbExist = checkDataBase();if (dbExist) {// do nothing - database already exist} else {// By calling following method// 1) an empty database will be created into the default system path of your application// 2) than we overwrite that database with our database.this.getReadableDatabase();try {copyDataBase();} catch (IOException e) {throw new Error("Error copying database");}}}/** * Check if the database already exist to avoid re-copying the file each time you open the application. * @return true if it exists, false if it doesn't */private boolean checkDataBase() {SQLiteDatabase checkDB = null;try {String myPath = DB_PATH + DB_NAME;checkDB = SQLiteDatabase.openDatabase(myPath, null,SQLiteDatabase.OPEN_READONLY);} catch (SQLiteException e) {// database does't exist yet.}if (checkDB != null) {checkDB.close();}return checkDB != null ? true : false;}/** * Copies your database from your local assets-folder to the just created * empty database in the system folder, from where it can be accessed and * handled. This is done by transfering bytestream. * */private void copyDataBase() throws IOException { // Open your local db as the input streamInputStream myInput = myContext.getAssets().open(DB_NAME); // Path to the just created empty dbString outFileName = DB_PATH + DB_NAME; // Open the empty db as the output streamOutputStream myOutput = new FileOutputStream(outFileName); // transfer bytes from the inputfile to the outputfilebyte[] buffer = new byte;int length;while ((length = myInput.read(buffer)) > 0) {myOutput.write(buffer, 0, length);} // Close the streamsmyOutput.flush();myOutput.close();myInput.close();}/** * Open the database * @throws SQLException */public void openDataBase() throws SQLException {String myPath = DB_PATH + DB_NAME;myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE);}/** * Close the database if exist */@Overridepublic synchronized void close() {if (myDataBase != null)myDataBase.close();super.close();}/** * Call on creating data base for example for creating tables at run time */@Overridepublic void onCreate(SQLiteDatabase db) {}/** * can used for drop tables then call onCreate(db) function to create tables again - upgrade */@Overridepublic void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {}// ----------------------- CRUD Functions ------------------------------/** * This function used to select the records from DB. * @param tableName * @param tableColumns * @param whereClase * @param whereArgs * @param groupBy * @param having * @param orderBy * @return A Cursor object, which is positioned before the first entry. */public Cursor selectRecordsFromDB(String tableName, String[] tableColumns,String whereClase, String whereArgs[], String groupBy,String having, String orderBy) {return myDataBase.query(tableName, tableColumns, whereClase, whereArgs,groupBy, having, orderBy);}/** * select records from db and return in list * @param tableName * @param tableColumns * @param whereClase * @param whereArgs * @param groupBy * @param having * @param orderBy * @return ArrayList> */public ArrayList> selectRecordsFromDBList(String tableName, String[] tableColumns,String whereClase, String whereArgs[], String groupBy,String having, String orderBy) {ArrayList> retList = new ArrayList>(); ArrayList list = new ArrayList(); Cursor cursor = myDataBase.query(tableName, tableColumns, whereClase, whereArgs,groupBy, having, orderBy); if (cursor.moveToFirst()) { do { list = new ArrayList(); for(int i=0; i 0;}/** * This function used to update the Record in DB. * @param tableName * @param initialValues * @param whereClause * @param whereArgs * @return 0 in case of failure otherwise return no of row(s) are updated */public int updateRecordsInDB(String tableName,ContentValues initialValues, String whereClause, String whereArgs[]) {return myDataBase.update(tableName, initialValues, whereClause, whereArgs);}/** * This function used to delete the Record in DB. * @param tableName * @param whereClause * @param whereArgs * @return 0 in case of failure otherwise return no of row(s) are deleted. */public int deleteRecordInDB(String tableName, String whereClause,String[] whereArgs) {return myDataBase.delete(tableName, whereClause, whereArgs);}// --------------------- Select Raw Query Functions ---------------------/** * apply raw Query * @param query * @param selectionArgs * @return Cursor */public Cursor selectRecordsFromDB(String query, String[] selectionArgs) {return myDataBase.rawQuery(query, selectionArgs);}/** * apply raw query and return result in list * @param query * @param selectionArgs * @return ArrayList> */public ArrayList> selectRecordsFromDBList(String query, String[] selectionArgs) { ArrayList> retList = new ArrayList>(); ArrayList list = new ArrayList(); Cursor cursor = myDataBase.rawQuery(query, selectionArgs); if (cursor.moveToFirst()) { do { list = new ArrayList(); for(int i=0; i<cursor.getColumnCount(); i++){ list.add( cursor.getString(i) ); } retList.add(list); } while (cursor.moveToNext()); } if (cursor != null && !cursor.isClosed()) { cursor.close(); } return retList; }}
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