Buttons not adding to the 'total' textview

Issue

I'm new to android studio, and have created 3 buttons. Code of 1 of the button are as follows,

    <Button
        android:id="@+id/button2"
        android:layout_width="160dp"
        android:layout_height="120dp"
        android:layout_marginBottom="434dp"
        android:contentDescription="5"
        android:text="$5"
        android:textSize="70sp"
        android:onClick="addTotal"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.39" /> 

MainActivity.java

public class MainActivity extends AppCompatActivity {

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

        // Initialize buttons
        final Button button1 = findViewById(R.id.button1);
        final Button button2 = findViewById(R.id.button2);
        final Button button3 = findViewById(R.id.button3);
        final TextView totalAmt = findViewById(R.id.totalAmt);

        public void addTotal (View v) {

        // $2 button
        button1.setOnClickListener((View view) -> {
            // Update total amount
            double total = Double.parseDouble(totalAmt.getText().toString()) + 2;
            String final_total = String.valueOf(total);
            totalAmt.setText(final_total);

        });

        // $5 button
        button2.setOnClickListener((View view) -> {
            // Update total amount
            double total = Double.parseDouble(totalAmt.getText().toString()) + 5;
            String final_total = String.valueOf(total);
            totalAmt.setText(final_total);

        });

        // $8 button
        button3.setOnClickListener((View view) -> {
            // Update total amount
            double total = Double.parseDouble(totalAmt.getText().toString()) + 8;
            String final_total = String.valueOf(total);
            totalAmt.setText(final_total);

        });
        }
    }
}

The purpose of the 3 buttons is to add either 2, 5, 8 to the total Textview

What am I doing wrong?

Thank you!

Solution

You Don't need to add onClick in XML file. You have the wrong declaration in MainActivity. Copy following code it will work properly now

xml

 <Button
        android:id="@+id/button2"
        android:layout_width="160dp"
        android:layout_height="120dp"
        android:layout_marginBottom="434dp"
        android:contentDescription="5"
        android:text="$5"
        android:textSize="70sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.39" /> 

MainActivity.java

public class MainActivity extends AppCompatActivity {

    Button button1, button2, button3;
    TextView totalAmt;
    double total = 0;

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

        // Initialize buttons
        button1 = findViewById(R.id.button1);
        button2 = findViewById(R.id.button2);
        button3 = findViewById(R.id.button3);
        totalAmt = findViewById(R.id.totalAmt);
        totalAmt.setText("0");
        
        addTotal();

    }

    public void addTotal() {

        // $2 button
        button1.setOnClickListener((View view) -> {
            // Update total amount
            total = Double.parseDouble(totalAmt.getText().toString()) + 2;
            String final_total = String.valueOf(total);
            totalAmt.setText(final_total);

        });

        // $5 button
        button2.setOnClickListener((View view) -> {
            // Update total amount
            total = Double.parseDouble(totalAmt.getText().toString()) + 5;
            String final_total = String.valueOf(total);
            totalAmt.setText(final_total);

        });

        // $8 button
        button3.setOnClickListener((View view) -> {
            // Update total amount
            total = Double.parseDouble(totalAmt.getText().toString()) + 8;
            String final_total = String.valueOf(total);
            totalAmt.setText(final_total);

        });
    }
}

Answered By - Yaqoob Bhatti