MainActivity.java

package com.anas.voicerecognitioncalculator;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

    TextView firstNumTextView;
    TextView secondNumTextView;
    TextView operatorTextView;
    TextView resultTextView;

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

        firstNumTextView = findViewById(R.id.firstNumTextView);
        secondNumTextView = findViewById(R.id.secondNumTextView);
        operatorTextView = findViewById(R.id.operatorTextView);
        resultTextView = findViewById(R.id.resultTextView);

        firstNumTextView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });

        secondNumTextView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });

        operatorTextView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

            }
        });
        
    }
}