我开发一个Android应用程序这给最近的一组的场所作为output.i希望能得到用户的当前位置，然后应用程序应该从数据库中获取信息，计算最近的位置。我的问题是我如何创建一个数据库，我应该在哪里创建它？什么是技术，我应该使用？从希望能跟大家快速响应。感谢所有...： - ）

I am developing an android application which gives the nearest set of places as output.i hope to get the current location of the user and then app should calculate nearest locations by getting information from a database. My question is how I create a database and where should I create it? What are the techniques i should use?Hope a quick response from u guys. Thanks all...:-)

推荐答案

张贴问题谷歌在它之前。有许多样品和导游与创建在Android中的数据库。

Before posting a question Google it. There are lots of samples and guides related to creating a database in Android.

请参阅下面的示例code：

See the sample code below:

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;
   }