public class MainActivity extends AppCompatActivity { private Button mAddButton; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); mAddButton = findViewById(R.id.addButton); mAddButton.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { openAddActivity(); } }); } public void openAddActivity(){ Intent intent = new Intent(this, Main2Activity.class); startActivity(intent); }