Android 1

how to add 2 numbers

1-go to activity_main.xml
2-make objects ( main_first  main_second  main_btn   main_tv_result
3-go to mainactivity.java

4-declare the variables

EditText et_first;EditText et_second;Button btn;

TextView tv_result;

5- link variables with objects
         et_first=findViewById(R.id.main_first);
        et_second=findViewById(R.id.main_second);
        btn=findViewById(R.id.main_btn);
        tv_result=findViewById(R.id.main_tv_result);

6-adding-firebase-to-android-app/