VM

private AppCompatActivity binding;
private ActivityViewModel viewModel;
 
public abstract ActivityViewModel onCreate();
public abstract @IdRes int getVariable();
public abstract @LayoutRes int getLayoutId();
 
@Override
public void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   bind();
}
 
public void bind() {
   binding = DataBindingUtil.setContentView(this, getLayoutId());
   this.viewModel = viewModel == null ? onCreate() : viewModel;
   binding.setVariable(getVariable(), viewModel);
   binding.executePendingBindings();
}