groovy implementation 'androidx.appcompat:appcompat:1.3.1' import androidx.appcompat.app.AppCompatActivity; public class MainActivity extends AppCompatActivity { // ... } <androidx.appcompat.widget.Toolbar android:id="@+id/toolbar" android:layout_width="match_parent" android:layout_height="?attr/actionBarSize" android:background="?attr/colorPrimary" /> import androidx.appcompat.app.AlertDialog; // ... AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this); builder.setTitle("Dialog") .setMessage("Hello, AppCompat!") .setPositiveButton("OK", null) .show();