Android Studio, TextView

Я создаю приложение, пытаясь установить результат серии нажатий на кнопки как текст TextView в макете. Моя проблема в том, что приложение вылетает, когда я нажимаю последнюю кнопку в последнем действии, где должен быть показан этот результат. Я размещаю код здесь, желаю, чтобы вы мне помогли. Спасибо.

XML:

<RelativeLayout xmlns:android = "http://schemas.android.com/apk/res/android"
    xmlns:app = "http://schemas.android.com/apk/res-auto"
    xmlns:tools = "http://schemas.android.com/tools"
    android:layout_width = "match_parent"
    android:layout_height = "match_parent"
    android:background = "@drawable/a"
    android:orientation = "vertical"
    tools:context = ".Riepilogo">

    <TextView
        android:id = "@+id/textView6"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"

        android:layout_alignParentTop = "true"
        android:layout_centerHorizontal = "true"
        android:text = "Riepilogo"
        android:textColor = "@android:color/holo_red_dark"
        android:textSize = "24sp"
        android:textStyle = "italic" />

    <Button
        android:id = "@+id/button"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/textView6"
        android:layout_alignParentStart = "true"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT1"
        android:text = "TAV. 1"
        android:textStyle = "bold"
        android:layout_alignParentLeft = "true" />

    <Button
        android:id = "@+id/button2"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button"
        android:layout_alignParentStart = "true"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT2"
        android:text = "TAV. 2"
        android:textStyle = "bold"
        android:layout_alignParentLeft = "true" />

    <Button
        android:id = "@+id/button16"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button2"
        android:layout_alignParentStart = "true"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT3"
        android:text = "TAV. 3"
        android:textStyle = "bold"
        android:layout_alignParentLeft = "true" />

    <Button
        android:id = "@+id/button17"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button16"
        android:layout_alignParentStart = "true"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT4"
        android:text = "TAV. 4"
        android:textStyle = "bold"
        android:layout_alignParentLeft = "true" />

    <Button
        android:id = "@+id/button19"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button17"
        android:layout_alignParentStart = "true"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT5"
        android:text = "TAV. 5"
        android:textStyle = "bold"
        android:layout_alignParentLeft = "true" />

    <Button
        android:id = "@+id/button20"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button19"
        android:layout_alignParentStart = "true"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT6"
        android:text = "TAV. 6"
        android:textStyle = "bold"
        android:layout_alignParentLeft = "true" />

    <Button
        android:id = "@+id/button22"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button20"
        android:layout_alignParentStart = "true"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT7"
        android:text = "TAV. 7"
        android:textStyle = "bold"
        android:layout_alignParentLeft = "true" />

    <Button
        android:id = "@+id/button23"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button22"
        android:layout_alignParentStart = "true"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT8"
        android:text = "TAV. 8"
        android:textStyle = "bold"
        android:layout_alignParentLeft = "true" />

    <Button
        android:id = "@+id/button24"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button23"
        android:layout_alignParentStart = "true"
        android:layout_alignParentLeft = "true"
        android:layout_marginStart = "0dp"
        android:layout_marginLeft = "0dp"
        android:layout_marginTop = "-2dp"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT9"
        android:text = "TAV. 9"
        android:textStyle = "bold" />

    <Button
        android:id = "@+id/button26"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button24"
        android:layout_alignParentStart = "true"
        android:layout_alignParentLeft = "true"
        android:layout_marginStart = "0dp"
        android:layout_marginLeft = "0dp"
        android:layout_marginTop = "2dp"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT10"
        android:text = "TAV. 10"
        android:textStyle = "bold" />

    <Button
        android:id = "@+id/button27"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button26"
        android:layout_alignParentStart = "true"
        android:layout_alignParentLeft = "true"
        android:layout_marginStart = "0dp"
        android:layout_marginLeft = "0dp"
        android:layout_marginTop = "-2dp"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT11"
        android:text = "TAV. 11"
        android:textStyle = "bold" />

    <Button
        android:id = "@+id/button28"
        android:layout_width = "wrap_content"
        android:layout_height = "wrap_content"
        android:layout_below = "@+id/button27"
        android:layout_alignParentStart = "true"
        android:layout_alignParentLeft = "true"
        android:layout_marginStart = "0dp"
        android:layout_marginLeft = "0dp"
        android:layout_marginTop = "4dp"
        android:layout_marginBottom = "-11dp"
        android:onClick = "OnButtonClickT12"
        android:text = "TAV. 12"
        android:textStyle = "bold" />

    <TextView
        android:id = "@+id/ttvv"
        android:layout_width = "228dp"
        android:layout_height = "455dp"
        android:layout_below = "@+id/textView6"
        android:layout_alignStart = "@+id/textView6"
        android:layout_alignLeft = "@+id/textView6"

        android:autoText = "false"
        android:clickable = "false"
        android:cursorVisible = "false"
        android:numeric = "decimal"
        android:text = "@string/rpg" />

</RelativeLayout>

ДЖАВА:

public class Riepilogo extends Tavolo {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_riepilogo);
        this.setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT); 
    }


    String t=String.valueOf(R.string.rpg); //rpg is the id of text in TextView


    public void OnButtonClickT1(View v){
        if (riep1.isEmpty() || tav1==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 1: "+riep1+" TOTALE: "+tav1+" EURO");

        }

    }
    public void OnButtonClickT2(View v){
        if (riep2.isEmpty() || tav2==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 2: "+riep2+" TOTALE: "+tav2+" EURO");}
    }
    public void OnButtonClickT3(View v){
        if (riep3.isEmpty() || tav3==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 3: "+riep3+" TOTALE: "+tav3+" EURO");}

    }
    public void OnButtonClickT4(View v){
        if (riep4.isEmpty() || tav4==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 4: "+riep4+" TOTALE: "+tav4+" EURO");}
    }
    public void OnButtonClickT5(View v){
        if (riep5.isEmpty() || tav5==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 5: "+riep5+" TOTALE: "+tav5+" EURO");}

    }
    public void OnButtonClickT6(View v){
        if (riep6.isEmpty() || tav6==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 6: "+riep6+" TOTALE: "+tav6+" EURO");}
    }
    public void OnButtonClickT7(View v){
        if (riep7.isEmpty() || tav7==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 7: "+riep7+" TOTALE: "+tav7+" EURO");}

    }
    public void OnButtonClickT8(View v){
        if (riep8.isEmpty() || tav8==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 8: "+riep8+" TOTALE: "+tav8+" EURO");}
    }
    public void OnButtonClickT9(View v){
        if (riep9.isEmpty() || tav9==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 9: "+riep9+" TOTALE: "+tav9+" EURO");}

    }
    public void OnButtonClickT10(View v){
        if (riep10.isEmpty() || tav10==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 10: "+riep10+" TOTALE: "+tav10+" EURO");}
    }
    public void OnButtonClickT11(View v){
        if (riep11.isEmpty() || tav11==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 11: "+riep11+" TOTALE: "+tav11+" EURO");}

    }
    public void OnButtonClickT12(View v){
        if (riep12.isEmpty() || tav12==0){
            Toast.makeText(getBaseContext(), "Niente da mostrare qui" ,
                    Toast.LENGTH_LONG).show();
        }
        else{
        t=("TAVOLO 12: "+riep12+" TOTALE: "+tav12+" EURO");}
    }

}