RemoteViews ListView setScrollPosition Misses

Question

I'm working on an app widget that contains a ListView. I want to be able to have it scroll to a specific row when it refreshes, and I'm using RemoteViews.setRelativeScrollPosition to do so, but it virtually always misses, either scrolling too far so the desired row is halfway off the top, or not far enough, so it's somewhere below the top of the widget. I want it to be lined up right at the top of the widget. I've tried using setScrollPosition instead of setRelativeScrollPosition, but then it doesn't scroll at all (the desired row is still shown, just farther down).

Am I doing something wrong, missing something, or is it just not possible to scroll a ListView to a specific position in a widget? I don't need the scrolling effect, I'd be happy if it just suddenly appeared in the right spot.

Here's my main widget layout:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:layout_height="match_parent"
          android:layout_width="match_parent"
          android:orientation="vertical"
          android:padding="@dimen/widget_margin"
          style="@style/AppTheme.WidgetMain">

<RelativeLayout android:id="@+id/title_layout"
    android:layout_height="wrap_content"
    android:layout_margin="1dp"
    android:layout_width="match_parent"
    style="@style/AppTheme.Title.Background">
    <TextView android:id="@+id/appwidget_title"
              android:contentDescription="@string/appwidget_title"
              android:layout_alignParentStart="true"
              android:layout_centerVertical="true"
              android:layout_height="wrap_content"
              android:layout_margin="1dp"
              android:layout_toStartOf="@+id/button_refresh"
              android:layout_width="wrap_content"
              android:paddingEnd="2dp"
              android:paddingStart="2dp"
              android:text="@string/appwidget_title"
              style="@style/AppTheme.Title" />
    <ImageButton android:id="@+id/button_refresh"
                 android:contentDescription="@string/button_refresh"
                 android:layout_centerVertical="true"
                 android:layout_height="wrap_content"
                 android:layout_marginEnd="20dp"
                 android:layout_toStartOf="@id/button_settings"
                 android:layout_width="wrap_content"
                 android:src="@drawable/ic_refresh"
                 style="@style/AppTheme.WidgetMain.Button" />
    <ImageButton android:id="@+id/button_settings"
                 android:contentDescription="@string/button_settings"
                 android:layout_alignParentEnd="true"
                 android:layout_centerVertical="true"
                 android:layout_height="wrap_content"
                 android:layout_marginEnd="10dp"
                 android:layout_width="wrap_content"
                 android:src="@android:drawable/ic_menu_preferences"
                 style="@style/AppTheme.WidgetMain.Button" />
</RelativeLayout>

<LinearLayout android:id="@+id/header_layout"
    android:layout_height="wrap_content"
    android:layout_marginEnd="1px"
    android:layout_marginStart="1px"
    android:layout_width="match_parent"
    android:orientation="horizontal"
    style="@style/AppTheme.Background" />

<ListView android:id="@+id/grid"
          android:divider="@null"
          android:layout_gravity="center"
          android:layout_height="0dp"
          android:layout_weight="1"
          android:layout_width="match_parent"
          android:scrollbars="none" />

</LinearLayout>

The ListView is populated in code with rows of the following layout:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
          android:id="@+id/box"
          android:clipChildren="false"
          android:clipToPadding="false"
          android:layout_gravity="fill"
          android:layout_height="83dp"
          android:layout_weight="1"
          android:layout_width="0dp"
          android:orientation="vertical"
          style="@style/AppTheme.Background">

</LinearLayout>

Then, I scroll it in my RemoteViewsService with the following:

@Override
    public void onDataSetChanged()
    {
        /* Scroll the view if the option is checked */
        if ( _context.getSharedPreferences(
            MainPreferencesFragment.getSharedPreferencesFileName( _appWidgetId ),
            Context.MODE_PRIVATE ).
            getBoolean( MainPreferencesFragment.PREF_KEY_SCROLL, false ) )
            {
                /* Set up the handler thread */
                final HandlerThread thread = new HandlerThread( "Widget-worker" );
                thread.start();
                Handler queue = new Handler( thread.getLooper() );
                /* Post a delayed action to the thread to set the scroll position */
                queue.postDelayed( new Runnable()
                {
                    @Override
                    public void run()
                    {
                        String packageName = _context.getPackageName();
                        RemoteViews rv = new RemoteViews( packageName, R.layout.widget );
                        rv.setRelativeScrollPosition( R.id.grid, _currentPosition );
                        AppWidgetManager appWidgetManager = AppWidgetManager.getInstance( _context );
                        appWidgetManager.partiallyUpdateAppWidget( _appWidgetId, rv );
                        thread.quitSafely();
                    }
                }, 100 );
            }
    }

Answer 1

Based on this response, I managed to scroll the ListView in the RemoteViews to a correctly aligned position using a two-step approach: first update the widget, and then, with a Handler, scroll to the desired position once the widget is (hopefully) populated and call partiallyUpdateAppWidget.

In your AppWidgetProvider, on your onUpdate method:

appWidgetManager.notifyAppWidgetViewDataChanged(widgetId, R.id.widget_list);
new Handler().postDelayed(new Runnable() {
    @Override
    public void run() {
        appWidgetManager.updateAppWidget(widgetId, remoteViews);
        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                remoteViews.setScrollPosition(R.id.widget_list, scrollPosition);
                appWidgetManager.partiallyUpdateAppWidget(widgetId, remoteViews);
            }
        }, 5000);
    }
}, 5000);