public class DoubleClickBackToContentTopListener implements View.OnClickListener {

 private final long delayTime = 300;
 private long lastClickTime = 0;
 private final IBackToContentTopView backToContentTopView;

 public interface IBackToContentTopView {
 void backToContentTop();
 }

 @Override
 public final void onClick(View v) {
 long nowClickTime = System.currentTimeMillis();
 if (nowClickTime - lastClickTime > delayTime) {
  lastClickTime = nowClickTime;
 } else {
  onDoubleClick(v);
 }
 }

 public DoubleClickBackToContentTopListener(@NonNull IBackToContentTopView backToContentTopView) {
 this.backToContentTopView = backToContentTopView;
 }

 public void onDoubleClick(View v) {
 backToContentTopView.backToContentTop();
 }

}

public class CNodeActivity extends Activity implements 
 DoubleClickBackToContentTopListener.IBackToContentTopView {

 private Toolbar toolbar;
 private ListView listView;

 @Override
 protected void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.activity_cnode);

 toolbar = (Toolbar) findViewById(R.id.toolbar);
 toolbar.setTitle(R.string.cnode);
 toolbar.setNavigationOnClickListener(v -> this.finish());
 toolbar.setOnClickListener(new DoubleClickBackToContentTopListener(this));

 listView = (ListView) findViewById(R.id.list_view);
 
 listView.setAdapter(//TODO);

 initData();

 }

 private void initData() {
 //TODO
 }

 @Override
 public void backToContentTop() {
 listView.setSelection(0);
 }

}