Active while an element is positioned within the visible area of the ScrollView.

<ScrollView>
    <StackPanel>
        <Each Items="{images}">
            <DockPanel Height="100">
                <Image Url="{source}" MemoryPolicy="UnloadUnused" Dock="Left"
                    Visibility="Hidden" ux:Name="theImage"/>
                <Text Value="{description}" TextWrapping="Wrap"/>

                <WhileVisibleInScrollView>
                    <Change theImage.Visibility="Visible"/>
                </WhileVisibleInScrollView>
            </DockPanel>
        </Each>
    </StackPanel>
</ScrollView>

This example will show the images only when they are actually in the visible area. Combined with the UnloadUnused memory policy this will allow the memory to be freed when they aren't visible to the user.

If the panel has a fixed height, as in this example, you could also collapse the text to save the calculation and rendering time.

You would also use this trigger if you wish to animate something within a ScrollView. There's no point in animating something the user can't actually see; using the trigger can save resources by not animating things that aren't visible.

Note that the element itself need not necessarily be visible, but just have a layout that positions it in the visible area. Visibility="Hidden" on a Visual does not prevent the activiation of this trigger.

This trigger responds to changes in scroll position. Layout changes on the element will also update the status but layout changes further up the tree may not update the status (we do not have an efficient way to monitor for global positioning changes).

Location

Namespace
Fuse.Triggers
Package
Fuse.Controls.ScrollView 2.6.0
Show Uno properties and methods

Interface of WhileVisibleInScrollView

Distance : float ux

The maximum allowed distance away from the visible area where this trigger remains active.

Inherited from WhileTrigger

BypassSetActive(bool) uno

Call in situations where the bypassing is forced. This should be rare since during rooting the normal bypass mechanism of the trigger will apply.

Invert : bool ux

Inverts the trigger so it will be active when it would normally be inactive, and vice versa.

Inherited from Trigger

BackwardAnimation : TriggerAnimation ux

Specifies an explicit backward animation instead of using the implied backward animation of the animators involved. Be aware that actions are not part of the animation.

CrossFadeDuration : double ux

If there is a transition between forward/backward playback and two timeilnes are being used (implicit or explicit) this specifies the cross-fade time.

Deactivate uno

Deactivates the trigger (target progress of 0).

Pulse uno

Plays the trigger to progress 1 then back to 0.

RequireLayout(Visual) uno

Indicates the trigger is bound to the layout of a visual. This will keep the trigger in Bypass mode until after the first layout of the element is obtained. This is required since layout does not happen in the same root grouping/update phase as the creation of the element, yet not having a layout should qualify as part of the rooting period.

Inherited from NodeGroupBase

Nodes : IList of Node ux

Nodes to add to the Parent when this trigger is any non-deactivated state (Progress > 0)

Inherited from Node

ContextParent : Node uno

The context parent is the semantic parent of this node. It is where non-UI structure should be resolved, like looking for the DataContext, a Navigation, or other semantic item.

FindNodeByName(Selector, Predicate<Node> (Node)) : Node uno

Finds the first node with a given name that satisfies the given acceptor. The serach algorithm works as follows: Nodes in the subtree are matched first, then it matches the nodes in the subtrees ofthe ancestor nodes by turn all the way to the root. If no matching node is found, the function returns null.

IsRootingStarted : bool uno

Whether rooting of this node has started. Note that even if this property returns true, rooting may not yet be completed for the node. See also IsRootingCompleted.

Name : Selector ux

Run-time name of the node. This property is automatically set using the ux:Name attribute.

OnRooted uno

If you override OnRooted you must call base.OnRooted() first in your derived class. No other processing should happen first, otherwise you might end up in an undefined state.

Inherited from PropertyObject

Inherited from object

Attached UX Attributes

GlobalKey (attached by Resource) : string ux

The ux:Global attribute creates a global resource that is accessible everywhere in UX markup.

Implemented Interfaces

IScriptObject uno

Interface for objects that can have a script engine representation