Android SQLite Where Clause NPE

Question

Query:

public List<Pontos> selectSpecific(String id) {
   List<Pontos> list = new ArrayList<Pontos>();
   Cursor cursor = this.db.query(TABLE_NAME, new String[] { "id", "name" },
           "id"+" = ?", new String[] { id }, null, null, null);
   if (cursor == null) {
          return list;
      }
   if (cursor.moveToFirst()) {
       do {
           Pontos p = new Pontos();
           p.id = cursor.getLong(0);
           p.name = cursor.getString(1);
           list.add(p); 
       } while (cursor.moveToNext());
  }
  if (cursor != null && !cursor.isClosed()) {
     cursor.close();
  }
   return list;

}

Fetching the result:

public class Showplace extends Activity {

   private String id;
   DataHelper dh = new DataHelper(Showplace.this);
   TextView txtTitle = null;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.showplace);

       Bundle extras = getIntent().getExtras();
       id = Integer.toString(extras.getInt("id"));
       txtTitle = (TextView) findViewById(R.id.txtTitle);
       List<Pontos> list = this.dh.selectSpecific(id);
       for(Pontos p : list){
           txtTitle.setText(p.getName().toString());
       }
   }

}

It's giving me an NPE, I think that's in this line:

Cursor cursor = this.db.query(TABLE_NAME, new String[] { "id", "name" },
       "id"+" = ?", new String[] { id }, null, null, null);

I tried various ways of doing this, searched a lot over StackOverflow and I can't seem to find a solution to this.

Edit:

LogCat:

03-02 10:22:09.244: E/AndroidRuntime(341): Uncaught handler: thread main exiting due to uncaught exception
03-02 10:22:09.304: E/AndroidRuntime(341): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.dotpro.android.bikevento/com.dotpro.android.bikevento.Showplace}: java.lang.NullPointerException
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2324)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2417)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.app.ActivityThread.access$2100(ActivityThread.java:116)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1794)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.os.Looper.loop(Looper.java:123)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.app.ActivityThread.main(ActivityThread.java:4203)
03-02 10:22:09.304: E/AndroidRuntime(341):  at java.lang.reflect.Method.invokeNative(Native Method)
03-02 10:22:09.304: E/AndroidRuntime(341):  at java.lang.reflect.Method.invoke(Method.java:521)
03-02 10:22:09.304: E/AndroidRuntime(341):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:791)
03-02 10:22:09.304: E/AndroidRuntime(341):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:549)
03-02 10:22:09.304: E/AndroidRuntime(341):  at dalvik.system.NativeStart.main(Native Method)
03-02 10:22:09.304: E/AndroidRuntime(341): Caused by: java.lang.NullPointerException
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.content.ContextWrapper.openOrCreateDatabase(ContextWrapper.java:193)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.database.sqlite.SQLiteOpenHelper.getWritableDatabase(SQLiteOpenHelper.java:98)
03-02 10:22:09.304: E/AndroidRuntime(341):  at com.dotpro.android.bikevento.DataHelper.<init>(DataHelper.java:28)
03-02 10:22:09.304: E/AndroidRuntime(341):  at com.dotpro.android.bikevento.Showplace.<init>(Showplace.java:14)
03-02 10:22:09.304: E/AndroidRuntime(341):  at java.lang.Class.newInstanceImpl(Native Method)
03-02 10:22:09.304: E/AndroidRuntime(341):  at java.lang.Class.newInstance(Class.java:1472)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.app.Instrumentation.newActivity(Instrumentation.java:1097)
03-02 10:22:09.304: E/AndroidRuntime(341):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2316)
03-02 10:22:09.304: E/AndroidRuntime(341):  ... 11 more

Answer 1

this line is wrong: DataHelper dh = new DataHelper(Showplace.this);

you should move dh = new DataHelper(Showplace.this); to onCreate method

Edit:

why? because if you initialize field dh as you do Activity is not fully created and the context is not valid