public class OpenTabsActivity extends AppCompatActivity {
 private LinearLayout buttons;
 private int tabno = -1;
 private Intent in;
 private Intent settings;
 private ArrayList<Button> list;
 private Button newTab;
 private Context ctx;

 @Override
 public void onCreate(Bundle savedInstanceState) {
     super.onCreate(savedInstanceState);
     setContentView(R.layout.activity_open_tabs);
     setSupportActionBar((Toolbar)findViewById(R.id.toolbar));
     buttons = findViewById(R.id.scroll_linear);
     in = new Intent();
     settings = new Intent();
     list = new ArrayList<Button>();
     newTab = findViewById(R.id.newtab);
     ctx = this;

     newTab.setOnClickListener(new View.OnClickListener() {
         @Override
         public void onClick(View v) {
             Button n = new Button(ctx);
             list.add(n);
             tabno += 1;
             Button nB = list.get(tabno);
             nB.setText(getText(R.string.newtab));
             // nB.id = tabno
             buttons.addView(nB);
         }
     });
 }
// ...
}