Scroll to given position in Android Leanback ListRow

Question

I'm using the Google Leanback widgets in an Android TV application. It utilizes a RowsFragment with ListRows in it.

What I'm trying to determine is if there is any way to programmatically scroll to a particular object within one of the rows. I've dug into the docs for the Leanback widgets but cannot find what I'm looking for.

Answer 1

I had a similar necessity: I needed to set the initial selected item in a ListRow. I ended up subclassing the ListRowPresenter like this:

import android.support.v17.leanback.widget.ListRowPresenter;
import android.support.v17.leanback.widget.RowPresenter;

public class CustomPresenter extends ListRowPresenter {

    private int mInitialSelectedPosition;

    public CustomPresenter(int position) {
        this.mInitialSelectedPosition = position;
    }

    @Override
    protected void onBindRowViewHolder(RowPresenter.ViewHolder holder, Object item) {
        super.onBindRowViewHolder(holder, item);

        ViewHolder vh = (ListRowPresenter.ViewHolder) holder;
        vh.getGridView().setSelectedPosition(mInitialSelectedPosition);
    }

}

Hopefully this will help you.

Answer 2

In the latest version of Leanback (think v23.3.0+), you can now specify not only the row position but also perform optional tasks on the row. In your case, the task would be programmatic selection like so:

BrowseFragment.setSelectedPosition(0, true, new ListRowPresenter.SelectItemViewHolderTask(2));

No need to implement custom list row presenters or anything

Answer 3

I've done it when I needed to implement "Return to the first item in a Row by pressing Back".

I was calling this method from Activity's onBackPressed().

If this method returns false we call Activity.super.onBackPressed(). If true - we don't.

    public boolean onBackPressed(){
        boolean consumeBack;

        int selectedRowPosition = getRowsFragment().getSelectedPosition();

        ListRowPresenter.ViewHolder selectedRow = (ListRowPresenter.ViewHolder) getRowsFragment().getRowViewHolder(selectedRowPosition);
        int selectedItemPosition = selectedRow.getSelectedPosition();

        if(selectedItemPosition == 0){
            consumeBack = false;
        } else {
            consumeBack = true;
            getRowsFragment().setSelectedPosition(selectedRowPosition, true, new ListRowPresenter.SelectItemViewHolderTask(0));
        }
        return consumeBack;
}

Instead of "0" you can set any position you need.