Question

I’m trying to scroll 2 listviews simultaneously using the setSelectionFromTop() method from the ListView API. Here’s my layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    >
    <ListView
    android:id="@+id/list_1"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="0.5"/>
    <ListView
    android:id="@+id/list_2"
    android:layout_width="0dp"
    android:layout_height="match_parent"
    android:layout_weight="0.5"/>
</LinearLayout>

and my Activity:

public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    final ListView listView1 = (ListView)findViewById(R.id.list_1);
    listView1.setAdapter(new ListAdapter());

    ListView listView2 = (ListView)findViewById(R.id.list_2);
    listView2.setAdapter(new ListAdapter());
    listView2.setOnScrollListener(new OnScrollListener() {

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem,
                int visibleItemCount, int totalItemCount) {
            // TODO Auto-generated method stub
            View v = view.getChildAt(0);
            final int top = (v == null) ? 0 : v.getTop();

            listView1.setSelectionFromTop(firstVisibleItem, top);
        }

        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
            // TODO Auto-generated method stub

        }

    });
}

Everything works fine and the scrolling is smooth. However, when I wrap list_1 in the xml file in a LinearLayout, the synchronized scrolling is broken. Is this a bug or am I forgetting to do something?

Note: The data sourcing the ListViews is taken from the ListView tutorial on the Android developer’s site and both ListViews are using instances of the same Adapter. Assume that I implemented the usage patterns for the Adapters correctly. Also, I’ve tried using RelativeLayout and even hard-coding the pixel values in. I still get the same issue.

Answer 1

I resolved this issue by re-factoring the layout and putting both listviews at the same level on in the view hierarchy.