public IPromise ensureVisible(RenderObject renderObject,
float alignment = 0.0f,
TimeSpan?duration = null,
Curve curve = null
)
{
D.assert(renderObject.attached);
RenderAbstractViewport viewport = RenderViewportUtils.of(renderObject);
D.assert(viewport != null);
float target = viewport.getOffsetToReveal(renderObject, alignment).offset.clamp(
this.minScrollExtent, this.maxScrollExtent);
if (target == this.pixels)
{
return(Promise.Resolved());
}
duration = duration ?? TimeSpan.Zero;
if (duration == TimeSpan.Zero)
{
this.jumpTo(target);
return(Promise.Resolved());
}
curve = curve ?? Curves.ease;
return(this.animateTo(target, duration: duration.Value, curve: curve));
}
void _scrollTo(BuildContext context)
{
if (this._scrolling)
{
return;
}
RenderObject contextObject = context.findRenderObject();
RenderAbstractViewport viewport = RenderViewportUtils.of(contextObject);
D.assert(viewport != null);
float margin = this._dropAreaExtent;
float scrollOffset = this._scrollController.offset;
float topOffset = Mathf.Max(this._scrollController.position.minScrollExtent,
viewport.getOffsetToReveal(contextObject, 0.0f).offset - margin
);
float bottomOffset = Mathf.Min(this._scrollController.position.maxScrollExtent,
viewport.getOffsetToReveal(contextObject, 1.0f).offset + margin
);
bool onScreen = scrollOffset <= topOffset && scrollOffset >= bottomOffset;
if (!onScreen)
{
this._scrolling = true;
this._scrollController.position.animateTo(
scrollOffset < bottomOffset ? bottomOffset : topOffset,
duration: this._scrollAnimationDuration,
curve: Curves.easeInOut
).Then(() => { this.setState(() => { this._scrolling = false; }); });
}
}
public Future ensureVisible(
RenderObject renderObject,
float alignment = 0.0f,
TimeSpan?duration = null,
Curve curve = null,
ScrollPositionAlignmentPolicy alignmentPolicy = ScrollPositionAlignmentPolicy.explicitPolicy
)
{
D.assert(renderObject.attached);
RenderAbstractViewport viewport = RenderViewportUtils.of(renderObject);
D.assert(viewport != null);
float target = 0f;
switch (alignmentPolicy)
{
case ScrollPositionAlignmentPolicy.explicitPolicy:
target = viewport.getOffsetToReveal(renderObject, alignment).offset.clamp(minScrollExtent, maxScrollExtent);
break;
case ScrollPositionAlignmentPolicy.keepVisibleAtEnd:
target = viewport.getOffsetToReveal(renderObject, 1.0f).offset.clamp(minScrollExtent, maxScrollExtent);
if (target < pixels)
{
target = pixels;
}
break;
case ScrollPositionAlignmentPolicy.keepVisibleAtStart:
target = viewport.getOffsetToReveal(renderObject, 0.0f).offset.clamp(minScrollExtent, maxScrollExtent);
if (target > pixels)
{
target = pixels;
}
break;
}
if (foundation_.FloatEqual(target, pixels))
{
return(Future.value());
}
duration = duration ?? TimeSpan.Zero;
if (duration == TimeSpan.Zero)
{
jumpTo(target);
return(Future.value());
}
curve = curve ?? Curves.ease;
return(animateTo(target, duration: duration.Value, curve: curve));
}
