coco
46 lines
1.9 KiB
Markdown
46 lines
1.9 KiB
Markdown
# Lifecycle
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Nodes have their own lifecycles, directly using the related classes of `androidx.lifecycle`.
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## Capping
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No node can be in a higher lifecycle state than any of its parents or the Android Activity it lives in.
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## On-screen & off-screen
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`NavModel` controls which children should be rendered on the screen and which should not with `NavModel.screenState`.
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The behaviour is customisable in `BaseNavModel` via `OnScreenStateResolver`.
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When a `NavElement` of the node is marked as on-screen, its lifecycle follows the parent node's lifecycle.
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The rendering status does not affect it – the node might not be added to Compose view and still be in a `RESUMED` state.
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When a `NavElement` of the node is marked as off-screen, the following might happen:
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- Its lifecycle is capped with `CREATED` (or `STOPPED`) in case of `ChildEntry.KeepMode.KEEP`.
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- The node is destroyed and its state is saved in case of `ChildEntry.KeepMode.SUSPEND`.
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`ChildEntry.KeepMode` settings can be configured for each `ParentNode` individually or globally via `Appyx.defaultChildKeepMode`.
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When a node is removed completely from `NavModel`, it will be in `DESTROYED` state.
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## Lifecycle changes
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The lifecycle state can be affected by:
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- The NavModel of the parent (adding or removing child `Nodes` and changing their on-screen status)
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- The parent's lifecycle state capping its children (transitive in the tree)
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- Android lifecycle (Activity) capping the whole tree
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## Back stack node lifecycle
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An example demonstrating the above:
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<img src="https://i.imgur.com/WlcQHqV.gif" width="200">
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Note that NavModels might have their slight differences (e.g. whether their operations remove a `Node` only from the view, or completely destroy it).
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In the case of the back stack:
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- The `Push` operation adds a new element and stashes the currently active one – the stashed one will be removed from the view & `STOPPED`
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- The `Pop` operation removes an element, the child `Node` will be `DESTROYED`
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