content: package android.support.constraint.app;
  
  import android.content.Intent;
  import android.os.Bundle;
  import android.view.View;
  import android.widget.Button;
  import android.widget.LinearLayout;
  import android.widget.ScrollView;
  
  import androidx.annotation.Nullable;
  import androidx.appcompat.app.AppCompatActivity;
  
  public class MainActivity extends AppCompatActivity implements View.OnClickListener {
      Class []demos = { Demo00vt.class};
  
      @Override
      protected void onCreate(@Nullable @org.jetbrains.annotations.Nullable Bundle savedInstanceState) {
          super.onCreate(savedInstanceState);
          ScrollView scrollView = new ScrollView(this);
          LinearLayout linearLayout = new LinearLayout(this);
          linearLayout.setOrientation(LinearLayout.VERTICAL);
  
          for (int i = 0; i < demos.length; i++) {
              Button button = new Button(this);
              button.setText(demos[i].getSimpleName());
              button.setTag(demos[i]);
              linearLayout.addView(button);
              button.setOnClickListener(this);
          }
          scrollView.addView(linearLayout);
          setContentView(scrollView);
      }
  
      @Override
      public void onClick(View view) {
          startActivity(new Intent(this,(Class) view.getTag()));
      }
  }
  