When accessing the variable method invocation?

Question

Java

public class MainActivity extends AppCompatActivity {

    TextView myText;

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

        myText = (TextView) findViewById(R.id.myText);

        myText.setText("test"); //Method invocation 'myText.setText("test")' may produce 'java.lang.NullPointerException'
    }

What is the problem?
In other modules, the same code works fine, I don't understand.
Tell me please

Answer 1

The IDE is telling you that there might not be myText in activity_main.xml. Then the variable will be null.