在android中创buildSQLite数据库
我想在我的应用程序中创build一个SQLite数据库，该数据库包含三个表格，我将在表格中添加数据并稍后使用它们。
但我喜欢保持数据库，就好像当第一次安装应用程序时，它会检查数据库是否存在，如果存在，它会更新它，否则创build一个新的数据库。
进一步，我正在做一个数据库类，以方便我的应用程序，所以我不会创build一个活动，我的数据库创build。
如果有可能的build议，请与我分享
更好的例子是[这里]
try { myDB = this.openOrCreateDatabase("DatabaseName", MODE_PRIVATE, null); /* Create a Table in the Database. */ myDB.execSQL("CREATE TABLE IF NOT EXISTS " + TableName + " (Field1 VARCHAR, Field2 INT(3));"); /* Insert data to a Table*/ myDB.execSQL("INSERT INTO " + TableName + " (Field1, Field2)" + " VALUES ('Saranga', 22);"); /*retrieve data from database */ Cursor c = myDB.rawQuery("SELECT * FROM " + TableName , null); int Column1 = c.getColumnIndex("Field1"); int Column2 = c.getColumnIndex("Field2"); // Check if our result was valid. c.moveToFirst(); if (c != null) { // Loop through all Results do { String Name = c.getString(Column1); int Age = c.getInt(Column2); Data =Data +Name+"/"+Age+"\n"; }while(c.moveToNext()); } 如果你想保持数据库之间的卸载，你必须把它放在SD卡上。 这是您的应用程序被删除时唯一不会被删除的地方。 但是作为回报，每次都可以被用户删除。
如果将数据库放在SD卡上，则不能再使用SQLiteOpenHelper ，但是可以使用该类的源代码和体系结构来了解如何实现数据库的创build，更新和打开。
这是直接使用的完整源代码，
public class CardDBDAO { protected SQLiteDatabase database; private DataBaseHelper dbHelper; private Context mContext; public CardDBDAO(Context context) { this.mContext = context; dbHelper = DataBaseHelper.getHelper(mContext); open(); } public void open() throws SQLException { if(dbHelper == null) dbHelper = DataBaseHelper.getHelper(mContext); database = dbHelper.getWritableDatabase(); } } public class DataBaseHelper extends SQLiteOpenHelper { private static final String DATABASE_NAME = "mydbnamedb"; private static final int DATABASE_VERSION = 1; public static final String CARDS_TABLE = "tbl_cards"; public static final String POICATEGORIES_TABLE = "tbl_poicategories"; public static final String POILANGS_TABLE = "tbl_poilangs"; public static final String ID_COLUMN = "id"; public static final String POI_ID = "poi_id"; public static final String POICATEGORIES_COLUMN = "poi_categories"; public static final String POILANGS_COLUMN = "poi_langs"; public static final String CARDS = "cards"; public static final String CARD_ID = "card_id"; public static final String CARDS_PCAT_ID = "pcat_id"; public static final String CREATE_PLANG_TABLE = "CREATE TABLE " + POILANGS_TABLE + "(" + ID_COLUMN + " INTEGER PRIMARY KEY," + POILANGS_COLUMN + " TEXT, " + POI_ID + " TEXT)"; public static final String CREATE_PCAT_TABLE = "CREATE TABLE " + POICATEGORIES_TABLE + "(" + ID_COLUMN + " INTEGER PRIMARY KEY," + POICATEGORIES_COLUMN + " TEXT, " + POI_ID + " TEXT)"; public static final String CREATE_CARDS_TABLE = "CREATE TABLE " + CARDS_TABLE + "(" + ID_COLUMN + " INTEGER PRIMARY KEY," + CARD_ID + " TEXT, " + CARDS_PCAT_ID + " TEXT, " + CARDS + " TEXT)"; private static DataBaseHelper instance; public static synchronized DataBaseHelper getHelper(Context context) { if (instance == null) instance = new DataBaseHelper(context); return instance; } private DataBaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onOpen(SQLiteDatabase db) { super.onOpen(db); if (!db.isReadOnly()) { // Enable foreign key constraints // db.execSQL("PRAGMA foreign_keys=ON;"); } } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(CREATE_PCAT_TABLE); db.execSQL(CREATE_PLANG_TABLE); db.execSQL(CREATE_CARDS_TABLE); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } } public class PoiLangDAO extends CardDBDAO { private static final String WHERE_ID_EQUALS = DataBaseHelper.ID_COLUMN + " =?"; public PoiLangDAO(Context context) { super(context); } public long save(PLang plang_data) { ContentValues values = new ContentValues(); values.put(DataBaseHelper.POI_ID, plang_data.getPoi_id()); values.put(DataBaseHelper.POILANGS_COLUMN, plang_data.getLangarr()); return database .insert(DataBaseHelper.POILANGS_TABLE, null, values); } public long update(PLang plang_data) { ContentValues values = new ContentValues(); values.put(DataBaseHelper.POI_ID, plang_data.getPoi_id()); values.put(DataBaseHelper.POILANGS_COLUMN, plang_data.getLangarr()); long result = database.update(DataBaseHelper.POILANGS_TABLE, values, WHERE_ID_EQUALS, new String[] { String.valueOf(plang_data.getId()) }); Log.d("Update Result:", "=" + result); return result; } public int deleteDept(PLang plang_data) { return database.delete(DataBaseHelper.POILANGS_TABLE, WHERE_ID_EQUALS, new String[] { plang_data.getId() + "" }); } public List<PLang> getPLangs1() { List<PLang> plang_list = new ArrayList<PLang>(); Cursor cursor = database.query(DataBaseHelper.POILANGS_TABLE, new String[] { DataBaseHelper.ID_COLUMN, DataBaseHelper.POI_ID, DataBaseHelper.POILANGS_COLUMN }, null, null, null, null, null); while (cursor.moveToNext()) { PLang plang_bin = new PLang(); plang_bin.setId(cursor.getInt(0)); plang_bin.setPoi_id(cursor.getString(1)); plang_bin.setLangarr(cursor.getString(2)); plang_list.add(plang_bin); } return plang_list; } public List<PLang> getPLangs(String pid) { List<PLang> plang_list = new ArrayList<PLang>(); String selection = DataBaseHelper.POI_ID + "=?"; String[] selectionArgs = { pid }; Cursor cursor = database.query(DataBaseHelper.POILANGS_TABLE, new String[] { DataBaseHelper.ID_COLUMN, DataBaseHelper.POI_ID, DataBaseHelper.POILANGS_COLUMN }, selection, selectionArgs, null, null, null); while (cursor.moveToNext()) { PLang plang_bin = new PLang(); plang_bin.setId(cursor.getInt(0)); plang_bin.setPoi_id(cursor.getString(1)); plang_bin.setLangarr(cursor.getString(2)); plang_list.add(plang_bin); } return plang_list; } public void loadPLangs(String poi_id, String langarrs) { PLang plangbin = new PLang(poi_id, langarrs); List<PLang> plang_arr = new ArrayList<PLang>(); plang_arr.add(plangbin); for (PLang dept : plang_arr) { ContentValues values = new ContentValues(); values.put(DataBaseHelper.POI_ID, dept.getPoi_id()); values.put(DataBaseHelper.POILANGS_COLUMN, dept.getLangarr()); database.insert(DataBaseHelper.POILANGS_TABLE, null, values); } } } public class PLang { public PLang() { super(); } public PLang(String poi_id, String langarrs) { // TODO Auto-generated constructor stub this.poi_id = poi_id; this.langarr = langarrs; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getPoi_id() { return poi_id; } public void setPoi_id(String poi_id) { this.poi_id = poi_id; } public String getLangarr() { return langarr; } public void setLangarr(String langarr) { this.langarr = langarr; } private int id; private String poi_id; private String langarr; }
public class MyDatabaseHelper extends SQLiteOpenHelper { private static final String DATABASE_NAME = "MyDb.db"; private static final int DATABASE_VERSION = 1; // Database creation sql statement private static final String DATABASE_CREATE_FRIDGE_ITEM = "create table FridgeItem(id integer primary key autoincrement,f_id text not null,food_item text not null,quantity text not null,measurement text not null,expiration_date text not null,current_date text not null,flag text not null,location text not null);"; public MyDatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } // Method is called during creation of the database @Override public void onCreate(SQLiteDatabase database) { database.execSQL(DATABASE_CREATE_FRIDGE_ITEM); } // Method is called during an upgrade of the database, @Override public void onUpgrade(SQLiteDatabase database,int oldVersion,int newVersion){ Log.w(MyDatabaseHelper.class.getName(),"Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); database.execSQL("DROP TABLE IF EXISTS FridgeItem"); onCreate(database); } } public class CommentsDataSource { private MyDatabaseHelper dbHelper; private SQLiteDatabase database; public String stringArray[]; public final static String FOOD_TABLE = "FridgeItem"; // name of table public final static String FOOD_ITEMS_DETAILS = "FoodDetails"; // name of table public final static String P_ID = "id"; // pid public final static String FOOD_ID = "f_id"; // id value for food item public final static String FOOD_NAME = "food_item"; // name of food public final static String FOOD_QUANTITY = "quantity"; // quantity of food item public final static String FOOD_MEASUREMENT = "measurement"; // measurement of food item public final static String FOOD_EXPIRATION = "expiration_date"; // expiration date of food item public final static String FOOD_CURRENTDATE = "current_date"; // date of food item added public final static String FLAG = "flag"; public final static String LOCATION = "location"; /** * * @param context */ public CommentsDataSource(Context context) { dbHelper = new MyDatabaseHelper(context); database = dbHelper.getWritableDatabase(); } public long insertFoodItem(String id, String name,String quantity, String measurement, String currrentDate,String expiration,String flag,String location) { ContentValues values = new ContentValues(); values.put(FOOD_ID, id); values.put(FOOD_NAME, name); values.put(FOOD_QUANTITY, quantity); values.put(FOOD_MEASUREMENT, measurement); values.put(FOOD_CURRENTDATE, currrentDate); values.put(FOOD_EXPIRATION, expiration); values.put(FLAG, flag); values.put(LOCATION, location); return database.insert(FOOD_TABLE, null, values); } public long insertFoodItemsDetails(String id, String name,String quantity, String measurement, String currrentDate,String expiration) { ContentValues values = new ContentValues(); values.put(FOOD_ID, id); values.put(FOOD_NAME, name); values.put(FOOD_QUANTITY, quantity); values.put(FOOD_MEASUREMENT, measurement); values.put(FOOD_CURRENTDATE, currrentDate); values.put(FOOD_EXPIRATION, expiration); return database.insert(FOOD_ITEMS_DETAILS, null, values); } public Cursor selectRecords(String id) { String[] cols = new String[] { FOOD_ID, FOOD_NAME, FOOD_QUANTITY, FOOD_MEASUREMENT, FOOD_EXPIRATION,FLAG,LOCATION,P_ID}; Cursor mCursor = database.query(true, FOOD_TABLE, cols, P_ID+"=?", new String[]{id}, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; // iterate to get each value. } public Cursor selectAllName() { String[] cols = new String[] { FOOD_NAME}; Cursor mCursor = database.query(true, FOOD_TABLE, cols, null, null, null, null, null, null); if (mCursor != null) { mCursor.moveToFirst(); } return mCursor; // iterate to get each value. } public Cursor selectAllRecords(String loc) { String[] cols = new String[] { FOOD_ID, FOOD_NAME, FOOD_QUANTITY, FOOD_MEASUREMENT, FOOD_EXPIRATION,FLAG,LOCATION,P_ID}; Cursor mCursor = database.query(true, FOOD_TABLE, cols, LOCATION+"=?", new String[]{loc}, null, null, null, null); int size=mCursor.getCount(); stringArray = new String[size]; int i=0; if (mCursor != null) { mCursor.moveToFirst(); FoodInfo.arrayList.clear(); while (!mCursor.isAfterLast()) { String name=mCursor.getString(1); stringArray[i]=name; String quant=mCursor.getString(2); String measure=mCursor.getString(3); String expir=mCursor.getString(4); String id=mCursor.getString(7); FoodInfo fooditem=new FoodInfo(); fooditem.setName(name); fooditem.setQuantity(quant); fooditem.setMesure(measure); fooditem.setExpirationDate(expir); fooditem.setid(id); FoodInfo.arrayList.add(fooditem); mCursor.moveToNext(); i++; } } return mCursor; // iterate to get each value. } public Cursor selectExpDate() { String[] cols = new String[] {FOOD_NAME, FOOD_QUANTITY, FOOD_MEASUREMENT, FOOD_EXPIRATION}; Cursor mCursor = database.query(true, FOOD_TABLE, cols, null, null, null, null, FOOD_EXPIRATION, null); int size=mCursor.getCount(); stringArray = new String[size]; if (mCursor != null) { mCursor.moveToFirst(); FoodInfo.arrayList.clear(); while (!mCursor.isAfterLast()) { String name=mCursor.getString(0); String quant=mCursor.getString(1); String measure=mCursor.getString(2); String expir=mCursor.getString(3); FoodInfo fooditem=new FoodInfo(); fooditem.setName(name); fooditem.setQuantity(quant); fooditem.setMesure(measure); fooditem.setExpirationDate(expir); FoodInfo.arrayList.add(fooditem); mCursor.moveToNext(); } } return mCursor; // iterate to get each value. } public int UpdateFoodItem(String id, String quantity, String expiration){ ContentValues values=new ContentValues(); values.put(FOOD_QUANTITY, quantity); values.put(FOOD_EXPIRATION, expiration); return database.update(FOOD_TABLE, values, P_ID+"=?", new String[]{id}); } public void deleteComment(String id) { System.out.println("Comment deleted with id: " + id); database.delete(FOOD_TABLE, P_ID+"=?", new String[]{id}); } }
为什么不参考文档或SDK附带的示例代码？ 示例中的代码介绍了如何使用链接的文档中描述的帮助程序类创build/更新/填充/读取数据库。
要了解如何在Android中使用sqlite数据库和最佳实践，请参阅 – 使用sqlite数据库的Android
有几个类，你应该知道，这将帮助你build模你的表和模型，即android.provider.BaseColumns
下面是一个表的例子
public class ProductTable implements BaseColumns { public static final String NAME = "name"; public static final String PRICE = "price"; public static final String TABLE_NAME = "products"; public static final String CREATE_QUERY = "create table " + TABLE_NAME + " (" + _ID + " INTEGER, " + NAME + " TEXT, " + PRICE + " INTEGER)"; public static final String DROP_QUERY = "drop table " + TABLE_NAME; public static final String SElECT_QUERY = "select * from " + TABLE_NAME; }
这里是代码
DatabaseMyHandler.class
public class DatabaseMyHandler extends SQLiteOpenHelper { private SQLiteDatabase myDataBase; private Context context = null; private static String TABLE_NAME = "customer"; public static final String DATABASE_NAME = "Student.db"; public final static String DATABASE_PATH = "/data/data/com.pkgname/databases/"; public static final int DATABASE_VERSION = 2; public DatabaseMyHandler(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); this.context = context; try { createDatabase(); } catch (IOException e) { e.printStackTrace(); } } @Override public void onCreate(SQLiteDatabase sqLiteDatabase) { myDataBase = sqLiteDatabase; } @Override public void onUpgrade(SQLiteDatabase sqLiteDatabase, int i, int i1) { } //Check database already exists or not private boolean checkDatabaseExists() { boolean checkDB = false; try { String PATH = DATABASE_PATH + DATABASE_NAME; File dbFile = new File(PATH); checkDB = dbFile.exists(); } catch (SQLiteException e) { } return checkDB; } //Create a empty database on the system public void createDatabase() throws IOException { boolean dbExist = checkDatabaseExists(); if (dbExist) { Log.v("DB Exists", "db exists"); } boolean dbExist1 = checkDatabaseExists(); if (!dbExist1) { this.getWritableDatabase(); try { this.close(); copyDataBase(); } catch (IOException e) { throw new Error("Error copying database"); } } } //Copies your database from your local assets-folder to the just created empty database in the system folder private void copyDataBase() throws IOException { String outFileName = DATABASE_PATH + DATABASE_NAME; OutputStream myOutput = new FileOutputStream(outFileName); InputStream myInput = context.getAssets().open(DATABASE_NAME); byte[] buffer = new byte[1024]; int length; while ((length = myInput.read(buffer)) > 0) { myOutput.write(buffer, 0, length); } myInput.close(); myOutput.flush(); myOutput.close(); } //Open Database public void openDatabase() throws SQLException { String PATH = DATABASE_PATH + DATABASE_NAME; myDataBase = SQLiteDatabase.openDatabase(PATH, null, SQLiteDatabase.OPEN_READWRITE); } //for insert data into database public void insertCustomer(String customer_id, String email_id, String password, String description, int balance_amount) { try { openDatabase(); SQLiteDatabase db = this.getWritableDatabase(); ContentValues contentValues = new ContentValues(); contentValues.put("customer_id", customer_id); contentValues.put("email_id", email_id); contentValues.put("password", password); contentValues.put("description", description); contentValues.put("balance_amount", balance_amount); db.insert(TABLE_NAME, null, contentValues); } catch (SQLException e) { e.printStackTrace(); } } public ArrayList<ModelCreateCustomer> getLoginIdDetail(String email_id, String password) { ArrayList<ModelCreateCustomer> result = new ArrayList<ModelCreateCustomer>(); //boolean flag = false; String selectQuery = "SELECT * FROM " + TABLE_NAME + " WHERE email_id='" + email_id + "' AND password='" + password + "'"; try { openDatabase(); Cursor cursor = myDataBase.rawQuery(selectQuery, null); //cursor.moveToFirst(); if (cursor.getCount() > 0) { if (cursor.moveToFirst()) { do { ModelCreateCustomer model = new ModelCreateCustomer(); model.setId(cursor.getInt(cursor.getColumnIndex("id"))); model.setCustomerId(cursor.getString(cursor.getColumnIndex("customer_id"))); model.setCustomerEmailId(cursor.getString(cursor.getColumnIndex("email_id"))); model.setCustomerPassword(cursor.getString(cursor.getColumnIndex("password"))); model.setCustomerDesription(cursor.getString(cursor.getColumnIndex("description"))); model.setCustomerBalanceAmount(cursor.getInt(cursor.getColumnIndex("balance_amount"))); result.add(model); } while (cursor.moveToNext()); } Toast.makeText(context, "Login Successfully", Toast.LENGTH_SHORT).show(); } // Log.e("Count", "" + cursor.getCount()); cursor.close(); myDataBase.close(); } catch (SQLException e) { e.printStackTrace(); } return result; } public void updateCustomer(String id, String email_id, String description, int balance_amount) { try { openDatabase(); SQLiteDatabase db = this.getWritableDatabase(); ContentValues contentValues = new ContentValues(); contentValues.put("email_id", email_id); contentValues.put("description", description); contentValues.put("balance_amount", balance_amount); db.update(TABLE_NAME, contentValues, "id=" + id, null); } catch (SQLException e) { e.printStackTrace(); } } }
Customer.class
public class Customer extends AppCompatActivity{ private DatabaseMyHandler mydb; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_customer); mydb = new DatabaseMyHandler(CreateCustomerActivity.this); mydb.insertCustomer("1", "a@a.com", "123", "test", 100); } }
一个简单的数据库实例将今日生活中的Todo List插入到DB中，并得到所有待办事项列表。
public class MyDatabaseHelper extends SQLiteOpenHelper { // Logcat tag private static final String LOG = "DatabaseHelper"; // Database Version private static final int DATABASE_VERSION = 1; // Database Name private static final String DATABASE_NAME = "SQLiteDemoDB"; // Table Names private static final String TABLE_TODO = "todos"; // column names private static final String KEY_ID = "id"; private static final String KEY_CREATED_AT = "created_at"; private static final String KEY_TODO = "todoDescr"; // ********************************************************************************************* public MyDatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(CREATE_TABLE_TODO); } // Upgrading database ************************************************************************** @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // Drop older table if existed db.execSQL("DROP TABLE IF EXISTS " + TABLE_TODO); // Create tables again onCreate(db); } // Creating Table TABLE_TEAM String CREATE_TABLE_TODO = "CREATE TABLE " + TABLE_TODO + "(" + KEY_ID + " integer primary key autoincrement, " + KEY_TODO + " text, " + KEY_CREATED_AT + " text" + ")"; // insert values of todo public boolean InsertTodoDetails(String todo, String createdAt) { SQLiteDatabase db = this.getWritableDatabase(); ContentValues contentValues = new ContentValues(); contentValues.put(KEY_TODO, todo); contentValues.put(KEY_CREATED_AT, createdAt); long rowInserted = db.insert(TABLE_TODO, null, contentValues); db.close(); return true; } // Select values of todo public Cursor GetAllTodoDetails() { SQLiteDatabase db = this.getReadableDatabase(); String query = "SELECT * FROM " + TABLE_TODO; Cursor mcursor = db.rawQuery(query, null); if (mcursor != null) { mcursor.moveToFirst(); } return mcursor; } }
我的活动保存并获取logging。
public class MyDbActivity extends AppCompatActivity { @Bind(R.id.edt_todo) EditText edtTodo; @Bind(R.id.btn_save) Button btnSave; MyDatabaseHelper db; @Bind(R.id.btn_getTodo) Button btnGetTodo; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_my_db); ButterKnife.bind(this); // creating database object db = new MyDatabaseHelper(this); } @OnClick(R.id.btn_save) public void onViewClicked() { String datetime = ""; try { SimpleDateFormat dateformat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); datetime = dateformat.format(new Date()); } catch (Exception e) { e.printStackTrace(); } db.InsertTodoDetails(edtTodo.getText().toString().trim(), datetime); } @OnClick(R.id.btn_getTodo) public void onGetTodoClicked() { String todos = ""; Cursor TodoList = db.GetAllTodoDetails(); if (TodoList.moveToFirst()) { do { if (todos.equals("")) { todos = TodoList.getString(TodoList.getColumnIndex("todoDescr")); } else { todos = todos + ", " + TodoList.getString(TodoList.getColumnIndex("todoDescr")); } // do what ever you want here } while (TodoList.moveToNext()); } TodoList.close(); Toast.makeText(this, "" + todos, Toast.LENGTH_SHORT).show(); } }
