Android View中的默认overScrollMode值

Question

根据Android 文档，overScrollMode的默认值为OVER_SCROLL_ALWAYS。

但是我的ListView似乎没有遵循这种行为。仅当有足够的内容在列表中滚动时，它才会显示过度滚动行为。

我尝试查看Android代码，发现View.java ref中的overScrollMode设置为OVER_SCROLL_IF_CONTENT_SCROLLS

我还检查了ListView和AbsListView的代码，以检查是否在任何地方都设置了overscrollmode，但是我什么也找不到。设置overScrollMode的唯一位置是在View.java中。

这是否意味着与此有关的Android文档不正确？我是否必须在列表视图中将overScrollMode显式设置为“ always”？

Answer 1

是的，Android文档实际上是不正确的。我确认了 如您在以下Android源代码中所见，默认情况下，过度滚动设置为if_content_scrolls。

/**
 * 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;
    }
}