goBack method

Implementation

void goBack() {
  _done = true;
  if (!mounted) return;
  if (!_visible) {
    _refreshing = false;
    return;
  }
  if (!_pointerUp) {
    // 手指还在屏幕上延迟执行动画
    setState(() {
      _needAnimate = true;
    });
    return;
  }
  _refreshing = false;
  _visibleExtent = 0;
}