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POHow to use SQLiteOpenHelper in Service
 

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  1. POHow to use SQLiteOpenHelper in Service
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    <p>Normally, in the activity, I use SQLiteOpenHelper like this</p> <pre><code>DatabaseHandler mDbHelper = new DatabaseHandler(getBaseContext()); </code></pre> <p>Now, I want to use SQLite in service. However, when I use the above code in the method of the Service class, it causes <strong>NullPointerException</strong> error.</p> <p>This is my Service class</p> <pre><code> public class MyService extends Service{ public void LoadDB(){ DatabaseHandler mDbHelper = new DatabaseHandler(getBaseContext()); ArrayList &lt;MyPosition&gt; positionlist = mDbHelper.getAllPositions(); **//error here** } private final IBinder mBinder = new LocalBinder(); public class LocalBinder extends Binder { MyService getService() { // Return this instance of LocalService so clients can call public methods return MyService.this; } } @Override public IBinder onBind(Intent intent) { return mBinder; } } This is the code that I call Service in MainActivity class public class MainActivity extends Activity { MyService mService; boolean mBound = false; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); activity = this; mService = new MyService(); doBindService(); if (mBound){ mService.LoadDB(); } } private ServiceConnection mConnection = new ServiceConnection() { @Override public void onServiceConnected(ComponentName className, IBinder service) { LocalBinder binder = (LocalBinder) service; mService = binder.getService(); mBound = true; } @Override public void onServiceDisconnected(ComponentName arg0) { mBound = false; } }; void doBindService() { bindService(new Intent(MainActivity.this, MyService.class), mConnection, Context.BIND_AUTO_CREATE); mBound = true; } void doUnbindService() { if (mBound) { // Detach our existing connection. unbindService(mConnection); mBound = false; } } } } </code></pre> <p>My DatabaseHandler class</p> <pre><code>package com.example.example10; import java.io.ByteArrayOutputStream; import java.util.ArrayList; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; import android.graphics.Bitmap; import android.graphics.BitmapFactory; public class DatabaseHandler extends SQLiteOpenHelper{ // All Static variables // Database Version private static final int DATABASE_VERSION = 1; // Database Name private static final String DATABASE_NAME = "ListPosition"; // Position table name private static final String TABLE_POSITIONS = "positions"; // Position Table Columns names public static final String KEY_ROWID = "_id"; private static final String KEY_ADDRESS = "address"; private static final String KEY_LONG = "longPos"; private static final String KEY_LAT = "latPos"; private static final String KEY_LASTVISITED = "lastVisited"; private static final String KEY_IMAGE = "image"; public DatabaseHandler(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } // Creating Tables @Override public void onCreate(SQLiteDatabase db) { String CREATE_POSITIONS_TABLE = "CREATE TABLE " + TABLE_POSITIONS + "(" + KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_ADDRESS + " TEXT," + KEY_LONG + " REAL, " + KEY_LAT + " REAL, " + KEY_LASTVISITED + " TEXT, " + KEY_IMAGE + " BLOB" +")"; db.execSQL(CREATE_POSITIONS_TABLE); } // Upgrading database @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // Drop older table if existed db.execSQL("DROP TABLE IF EXISTS " + TABLE_POSITIONS); // Create tables again onCreate(db); } /** * All CRUD(Create, Read, Update, Delete) Operations */ // Adding new position void addPosition(MyPosition position) { SQLiteDatabase db = this.getWritableDatabase(); ContentValues values = new ContentValues(); values.put(KEY_ADDRESS, position.GetAddress()); values.put(KEY_LONG, position.GetLongPos()); values.put(KEY_LAT, position.GetLatPos()); values.put(KEY_LASTVISITED, position.GetLastVisited()); ByteArrayOutputStream stream = new ByteArrayOutputStream(); position.GetImage().compress(Bitmap.CompressFormat.PNG, 100, stream); byte[] imageInByte = stream.toByteArray(); values.put(KEY_IMAGE, imageInByte); // Inserting Row db.insert(TABLE_POSITIONS, null, values); db.close(); // Closing database connection } // Getting All Positions public ArrayList &lt;MyPosition&gt; getAllPositions() { ArrayList &lt;MyPosition&gt; position_list = new ArrayList &lt;MyPosition&gt;(); // Select All Query String selectQuery = "SELECT * FROM " + TABLE_POSITIONS; SQLiteDatabase db = this.getWritableDatabase(); Cursor cursor = db.rawQuery(selectQuery, null); // looping through all rows and adding to list if (cursor.moveToFirst()) { do { MyPosition position = new MyPosition(); position.SetAddress(cursor.getString(1)); position.SetLongPos(cursor.getFloat(2)); position.SetLatPos(cursor.getFloat(3)); position.SetLastVisited(cursor.getString(4)); byte[] imagebyte = cursor.getBlob(5); Bitmap image = BitmapFactory.decodeByteArray(imagebyte, 0, imagebyte.length); position.SetImage(image); // Adding position to list position_list.add(position); } while (cursor.moveToNext()); } // return position list return position_list; } // Updating single position public int updatePosition(MyPosition position, int index) { SQLiteDatabase db = this.getWritableDatabase(); ContentValues values = new ContentValues(); values.put(KEY_ADDRESS, position.GetAddress()); values.put(KEY_LONG, position.GetLongPos()); values.put(KEY_LAT, position.GetLatPos()); values.put(KEY_LASTVISITED, position.GetLastVisited()); ByteArrayOutputStream stream = new ByteArrayOutputStream(); position.GetImage().compress(Bitmap.CompressFormat.PNG, 100, stream); byte[] imageInByte = stream.toByteArray(); values.put(KEY_IMAGE, imageInByte); // updating row return db.update(TABLE_POSITIONS, values, KEY_ROWID + "=" + (index + 1), null); } // Deleting single position public void deletePosition(MyPosition position, int index) { SQLiteDatabase db = this.getWritableDatabase(); db.delete(TABLE_POSITIONS, KEY_ROWID + "=" + (index + 1), null); db.close(); } // Getting position Count public int getPositionCount() { String countQuery = "SELECT * FROM " + TABLE_POSITIONS; SQLiteDatabase db = this.getReadableDatabase(); Cursor cursor = db.rawQuery(countQuery, null); int count = cursor.getCount(); cursor.close(); // return count return count; } // Getting single position MyPosition getPosition(int index) { SQLiteDatabase db = this.getReadableDatabase(); Cursor cursor = db.query(TABLE_POSITIONS, new String[] { KEY_ADDRESS, KEY_LONG, KEY_LAT, KEY_LASTVISITED, KEY_IMAGE}, KEY_ROWID + "=?", new String[] { String.valueOf(index) }, null, null, null, null); if (cursor != null) cursor.moveToFirst(); Bitmap image = BitmapFactory.decodeByteArray(cursor.getBlob(5), 0, cursor.getBlob(5).length); MyPosition position = new MyPosition(cursor.getString(1), cursor.getDouble(2), cursor.getDouble(3), cursor.getString(4), image); // return contact return position; } } </code></pre> <p>Do you have any suggestion for me? Thanks all.</p>
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