My APP crashes as soon as launch on Android Emulator on Android Studio

Question

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at com.example.converter.MainActivity.onCreate(MainActivity.java:30)

 that's where it shows error         btnMiles.setOnClickListener(new View.OnClickListener() 

Answer 1

Hi please check the code, might be missing

in XML

    <Button
            android:id="@+id/btnMiles"
     ..../>

in Java

Button btnMiles = (Button)findViewById(R.id.btnMiles);