View — Lifecycle

A view moves through a well-defined lifecycle as it enters and leaves the visual tree. The sequence is:

OnAttach
  OnActivate
    AnimateCore  ←─┐
    MeasureCore    │  repeating per frame
    ArrangeCore    │  (see Layout)
    RenderCore   ──┘
  OnDeactivate
OnDetach

Attach / Detach

These events fire when the view is connected to (or disconnected from) a live platform window.

protected virtual void OnAttach(ref AttachEventRef e) { }
protected virtual void OnDetach(ref DetachEventRef e) { }

OnAttach is the right place to acquire resources that require platform context — e.g. loading a bitmap via IBitmapFactory or caching a font metric. OnDetach should release them.

Subtree traversal is top-down for attach (parent before children) and bottom-up for detach (children before parent).

Activate / Deactivate

These events fire when the view becomes live (will receive events, animate, and render) or dormant.

protected virtual void OnActivate()   { }
protected virtual void OnDeactivate() { }

A view can be in the tree but inactive — for example, a view held in a virtualising panel's recycle pool. OnActivate is the right place to start animations or subscribe to data sources. OnDeactivate should stop them.

Subtree traversal is top-down for activate and bottom-up for deactivate, matching the attach/detach convention.

Flags

The Attached and Active bits on ViewFlags reflect the current state and are set/cleared automatically by the subtree helpers:

Flag	Set by	Cleared by
ViewFlags.Attached	AttachSubtree	DetachSubtree
ViewFlags.Active	ActivateSubtree	DeactivateSubtree

See State for the full flag reference.

The frame loop

While active, a view participates in the repeating frame loop via the layout pipeline. See Layout for how AnimateCore, MeasureCore, ArrangeCore, and RenderCore fit into that loop.