Flutter 擴充套件NestedScrollView (三)下拉重新整理的解決
解決點之前的2個問題。開心的上專案試了下。完美。
但是在使用官方的下拉重新整理RefreshIndicator 發現沒法使用。
默默打開了原始碼,我們再來看一看。。
首先,我除錯到這個,發現notification.depth不為0,其實也好理解,因為NestedScrollView裡面有很多能滾動的東西。預設的RefreshIndicator要求的是必須是第一層的它才其效果。
/// A [ScrollNotificationPredicate] that checks whether /// `notification.depth == 0`, which means that the notification did not bubble /// through any intervening scrolling widgets. bool defaultScrollNotificationPredicate(ScrollNotification notification) { return notification.depth == 0; } 複製程式碼
那麼我改成,再試試呢?
bool defaultScrollNotificationPredicate(ScrollNotification notification) { return true; return notification.depth == 0; } 複製程式碼
在_handleScrollNotification方法中,我們可以看到會有很多ScrollNotification進來,不同的,當你滑動在一個不能滾動的list裡面的時候,獲取的viewportDimension是為0.。這會覆蓋掉之前有viewportDimension的值。
所以我做了以下改動
double maxContainerExtent = 0.0; bool _handleScrollNotification(ScrollNotification notification) { if (!widget.notificationPredicate(notification)) return false; maxContainerExtent = math.max( notification.metrics.viewportDimension, this.maxContainerExtent); if (notification is ScrollStartNotification && notification.metrics.extentBefore == 0.0 && _mode == null && _start(notification.metrics.axisDirection)) { setState(() { _mode = _RefreshIndicatorMode.drag; }); return false; } bool indicatorAtTopNow; switch (notification.metrics.axisDirection) { case AxisDirection.down: indicatorAtTopNow = true; break; case AxisDirection.up: indicatorAtTopNow = false; break; case AxisDirection.left: case AxisDirection.right: indicatorAtTopNow = null; break; } if (indicatorAtTopNow != _isIndicatorAtTop) { if (_mode == _RefreshIndicatorMode.drag || _mode == _RefreshIndicatorMode.armed) _dismiss(_RefreshIndicatorMode.canceled); } else if (notification is ScrollUpdateNotification) { if (_mode == _RefreshIndicatorMode.drag || _mode == _RefreshIndicatorMode.armed) { if (notification.metrics.extentBefore > 0.0) { _dismiss(_RefreshIndicatorMode.canceled); } else { _dragOffset -= notification.scrollDelta; _checkDragOffset(maxContainerExtent); } } if (_mode == _RefreshIndicatorMode.armed && notification.dragDetails == null) { // On iOS start the refresh when the Scrollable bounces back from the // overscroll (ScrollNotification indicating this don't have dragDetails // because the scroll activity is not directly triggered by a drag). _show(); } } else if (notification is OverscrollNotification) { if (_mode == _RefreshIndicatorMode.drag || _mode == _RefreshIndicatorMode.armed) { _dragOffset -= notification.overscroll / 2.0; _checkDragOffset(maxContainerExtent); } } else if (notification is ScrollEndNotification) { switch (_mode) { case _RefreshIndicatorMode.armed: _show(); break; case _RefreshIndicatorMode.drag: _dismiss(_RefreshIndicatorMode.canceled); break; default: // do nothing break; } } return false; } 複製程式碼
對於NestedScrollView 來說。我們只需要關注最大能滾動viewportDimension,用這個來驅動整個下拉重新整理.
Sample Code
用法跟官方一致
return NestedScrollViewRefreshIndicator( onRefresh: onRefresh, child: extended.NestedScrollView( 複製程式碼
最後放上 Flutter%2Ftree%2Fmaster%2Fextended_nested_scroll_view" rel="nofollow,noindex"> Github extended_nested_scroll_view ,如果你有更好的方式解決這個問題或者有什麼不明白的地方,都請告訴我,由衷感謝。