Как сделать базу данных для моего приложения Android

Question

Я разрабатываю приложение для Android, которое дает ближайший набор мест в качестве output.i надеется получить текущее местоположение пользователя, а затем приложение должно вычислить ближайшие местоположения, получив информацию от база данных. Мой вопрос в том, как я создаю базу данных и где ее создать? Каковы методы, которые я должен использовать? Надеюсь на быстрый ответ от ребят. Спасибо всем ... :-)

Answer 1

Поиск «SQLite для Android» и мне кулачно взгляните на Android Deveoper page for storage.

Answer 2

Перед публикацией вопроса Google it. Существует множество примеров и руководств, связанных с созданием базы данных в Android.

Смотрите пример кода ниже:

public class DBAdapter extends SQLiteOpenHelper { 

private static String DB_PATH = ""; 
private static final String DB_NAME = "Databasefilename.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/"; 
    try { 
     createDataBase(); 
    } catch (IOException e) { 
     // TODO Auto-generated catch block 
     e.printStackTrace(); 
    } 
    // 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 stream 
    InputStream myInput = myContext.getAssets().open(DB_NAME); 
     // Path to the just created empty db 
    String outFileName = DB_PATH + DB_NAME; 
     // Open the empty db as the output stream 
    OutputStream myOutput = new FileOutputStream(outFileName); 
     // transfer bytes from the inputfile to the outputfile 
    byte[] buffer = new byte[1024]; 
    int length; 

    while ((length = myInput.read(buffer)) > 0) 
    { 
     myOutput.write(buffer, 0, length); 
    } 
     // Close the streams 
    myOutput.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 
*/ 
@Override 
public synchronized void close() 
{ 
    if (myDataBase != null) 
     myDataBase.close(); 
    super.close(); 
} 

/** 
* Call on creating data base for example for creating tables at run time 
*/ 
@Override 
public void onCreate(SQLiteDatabase db) 
{ 

} 

/** 
* can used for drop tables then call onCreate(db) function to create tables again - upgrade 
*/ 
@Override 
public 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<ArrayList<String>> 
*/ 
public ArrayList<ArrayList<String>> selectRecordsFromDBList(String tableName, String[] tableColumns,String whereClase, String whereArgs[], String groupBy,String having, String orderBy) 
{  

    ArrayList<ArrayList<String>> retList = new ArrayList<ArrayList<String>>(); 
     ArrayList<String> list = new ArrayList<String>(); 
     Cursor cursor = myDataBase.query(tableName, tableColumns, whereClase, whereArgs, 
       groupBy, having, orderBy);   
     if (cursor.moveToFirst()) 
     { 
     do 
      { 
      list = new ArrayList<String>(); 
      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; 

} 

/** 
* This function used to insert the Record in DB. 
* @param tableName 
* @param nullColumnHack 
* @param initialValues 
* @return the row ID of the newly inserted row, or -1 if an error occurred 
*/ 
public long insertRecordsInDB(String tableName, String nullColumnHack,ContentValues initialValues) 
{ 

    return myDataBase.insert(tableName, nullColumnHack, initialValues); 
} 

/** 
* This function used to update the Record in DB. 
* @param tableName 
* @param initialValues 
* @param whereClause 
* @param whereArgs 
* @return true/false on updating one or more records 
*/ 
public boolean updateRecordInDB(String tableName,ContentValues initialValues, String whereClause, String whereArgs[]) 
{ 
    return myDataBase.update(tableName, initialValues, whereClause,whereArgs) > 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<ArrayList<String>> 
*/ 
public ArrayList<ArrayList<String>> selectRecordsFromDBList(String query, String[] selectionArgs) 
{   
     ArrayList<ArrayList<String>> retList = new ArrayList<ArrayList<String>>(); 
     ArrayList<String> list = new ArrayList<String>(); 
     Cursor cursor = myDataBase.rawQuery(query, selectionArgs);    
     if (cursor.moveToFirst()) { 
     do{ 
      list = new ArrayList<String>(); 
      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; 
    }