Default overScrollMode value in Android View

Question

Per Android documentation, the default value for overScrollMode is OVER_SCROLL_ALWAYS.

But my ListView did not seem to follow this behavior. It only shows overscrolling behavior when there is enough content to scroll in the list.

I tried to look into the Android code and found that the overScrollMode is set to OVER_SCROLL_IF_CONTENT_SCROLLS in View.java ref

I also checked the code for ListView and AbsListView to check if the overscrollmode was being set anywhere but I couldn't find anything. The only place where overScrollMode is set is in View.java.

Does this mean that the Android documentation for this is incorrect? Do I have to explicitly set overScrollMode to 'always' in my list view?

Answer 1

Yes, the Android documentation is in fact incorrect. I confirmed it. As you can see in the below code from Android source, overscrolling is set to if_content_scrolls by default.

/**
 * Simple constructor to use when creating a view from code.
 *
 * @param context The Context the view is running in, through which it can
 *        access the current theme, resources, etc.
 */
public View(Context context) {
    mContext = context;
    mResources = context != null ? context.getResources() : null;
    mViewFlags = SOUND_EFFECTS_ENABLED | HAPTIC_FEEDBACK_ENABLED;
    // Set some flags defaults
    mPrivateFlags2 =
        (LAYOUT_DIRECTION_DEFAULT << PFLAG2_LAYOUT_DIRECTION_MASK_SHIFT) |
        (TEXT_DIRECTION_DEFAULT << PFLAG2_TEXT_DIRECTION_MASK_SHIFT) |
        (PFLAG2_TEXT_DIRECTION_RESOLVED_DEFAULT) |
        (TEXT_ALIGNMENT_DEFAULT << PFLAG2_TEXT_ALIGNMENT_MASK_SHIFT) |
        (PFLAG2_TEXT_ALIGNMENT_RESOLVED_DEFAULT) |
        (IMPORTANT_FOR_ACCESSIBILITY_DEFAULT << PFLAG2_IMPORTANT_FOR_ACCESSIBILITY_SHIFT);
    mTouchSlop = ViewConfiguration.get(context).getScaledTouchSlop();
    setOverScrollMode(OVER_SCROLL_IF_CONTENT_SCROLLS);
    mUserPaddingStart = UNDEFINED_PADDING;
    mUserPaddingEnd = UNDEFINED_PADDING;

    if (!sCompatibilityDone && context != null) {
        final int targetSdkVersion = context.getApplicationInfo().targetSdkVersion;

        // Older apps may need this compatibility hack for measurement.
        sUseBrokenMakeMeasureSpec = targetSdkVersion <= JELLY_BEAN_MR1;

        // Older apps expect onMeasure() to always be called on a layout pass, regardless
        // of whether a layout was requested on that View.
        sIgnoreMeasureCache = targetSdkVersion < KITKAT;

        sCompatibilityDone = true;
    }
}