Werte vom Dialog in die MainActivity schicken

//BuilderAndDialog ist die zweite Klasse
private BuilderAndDialog dialog = new BuilderAndDialog();


public void onButtonClickMain(View view) {


		switch (view.getId()) {


		case R.id.btn_neue_gruppe_erstellen: {
 
                        //Der Aufruf für das Erstellen des Dialogs
			dialog.dialogNeueGruppeErstellen(context);
			break;
		}

private Dialog dialog;
	private Button button;
	private Button button2;
	private String string;
	private String string2;
	private String string3;
	private EditText editText;
	private EditText editText2;
	private EditText editText3;
	private Intent intent;
	private MainActivity mainActivity;




public void dialogNeueGruppeErstellen(Context context) {


		mainActivity = new MainActivity();


                //Dialog initialisieren
		dialog = new Dialog(context);
		dialog.setContentView(R.layout.neue_gruppe_erstellen);
		dialog.getWindow().setGravity(Gravity.TOP);
		dialog.setTitle("Gruppe erstellen");


                //Views im Dialog bekommen
		button = (Button) dialog.findViewById(R.id.btn_abbrechen);
		button2 = (Button) dialog.findViewById(R.id.btn_ok);
		editText = (EditText) dialog.findViewById(R.id.edt_gruppen_name);
		editText2 = (EditText) dialog.findViewById(R.id.edt_erste_sprache);
		editText3 = (EditText) dialog.findViewById(R.id.edt_zweite_sprache);


                //Der intent
		intent = new Intent(BuilderAndDialog.this, MainActivity.class);


		dialog.show();


                //Button für Dialog schließen
		button.setOnClickListener(new OnClickListener() {


			public void onClick(View v) {


				dialog.dismiss();
			}
		});


                //Hier werden die Werte hinzugefügt
                //OK-Button, welcher auch benutzt wird um die Daten in der Main zu schicken
		button2.setOnClickListener(new OnClickListener() {
			public void onClick(View v) {


				string = editText.getText().toString();
				string2 = editText2.getText().toString();
				string3 = editText3.getText().toString();


				intent.putExtra("string", string);
				intent.putExtra("string2", string2);
				intent.putExtra("string3", string3);


				startActivity(intent);


                                Das wird aufgerufen um die Daten dann zu übergeben
				mainActivity.gibDaten();
			}
		});
	}

public void gibDaten() {


		bundle = getIntent().getExtras();
		string = bundle.getString(string);
		string2 = bundle.getString(string2);
		string3 = bundle.getString(string3);


                //Test um zu schauen ob die Daten in der Main benutzbar sind
		textView.setText(string2);
	}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main_layout_01"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@android:color/black"
    android:orientation="vertical" >




    <LinearLayout
        android:id="@+id/main_layout_02"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1" >




        <Button
            android:id="@+id/main_btn_decks"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:background="@drawable/custom_button_blau"
            android:text="@string/main_btn_decks"
            android:textSize="9pt" />


        <Button
            android:id="@+id/main_btn_liste"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:background="@drawable/custom_button_blau"
            android:text="@string/main_btn_liste"
            android:textSize="9pt" />


        <Button
            android:id="@+id/main_btn_training"
            android:layout_width="0dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:background="@drawable/custom_button_blau"
            android:text="@string/main_btn_training"
            android:textSize="9pt" />
    </LinearLayout>


    <TextView
        android:id="@+id/main_txt_deck_auswaehlen"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="0.6"
        android:gravity="center"
        android:text="@string/main_txt_deck_auswaehlen"
        android:textColor="@android:color/white"
        android:textSize="9pt" />


    <ScrollView
        android:id="@+id/main_scroll_01"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="5.4" >


        <LinearLayout
            android:id="@+id/main_layout_03"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >


            <Button
                android:id="@+id/main_btn_neuen_deck_erstellen"
                android:layout_width="match_parent"
                android:layout_height="50dp"
                android:background="@drawable/custom_button_rot"
                android:text="@string/main_btn_neuen_deck_erstellen"
                android:textSize="9pt" />
        </LinearLayout>
    </ScrollView>


    <Button
        android:id="@+id/main_btn_weiter"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:background="@drawable/custom_button_gruen"
        android:text="@string/main_btn_weiter"
        android:textSize="9pt" />


</LinearLayout>