Surviving configuration changes

To retain objects during configuration change you can use the RetainedInstanceStore class.

How does it work?

The RetainedInstanceStore stores objects within a singleton.

Every Node has access to the RetainedInstanceStore and manages these cases automatically:

• The Activity is recreated: the retained instance is returned instead of a new instance.
• The Activity is destroyed: the retained instance is removed and disposed.

Example

Appyx provides extension methods on the NodeContext class (an instance which is passed to every Node upon creation) to access the RetainedInstanceStore. You can use these to:

• Create your retained objects (factory)
• Define cleanup mechanisms (disposer) to be run when the retained object will be removed on Activity destroy.

You can opt to use the Builder pattern to provide dependencies to your Node and separate this logic:

Note: to use the rx2/rx3 getRetainedDisposable extension methods you see below, you need to add the relevant gradle dependencies. Please refer to Downloads.

import com.bumble.appyx.navigation.builder.Builder
import com.bumble.appyx.navigation.modality.NodeContext
import com.bumble.appyx.navigation.node.Node
import com.bumble.appyx.navigation.store.getRetainedInstance
import com.bumble.appyx.utils.interop.rx2.store.getRetainedDisposable

class YourNodeBuilder : Builder<YourPayload>() {

    override fun build(nodeContext: NodeContext, payload: YourPayload): Node {
        // Case 1:
        // If your type implements an rx2/rx3 Disposable,
        // you don't need to pass a disposer:
        val retainedFoo = nodeContext.getRetainedDisposable {
            Foo(payload)
        }

        // Case 2:
        // If your type doesn't implement an rx2/rx3 Disposable,
        // you can define a custom cleanup mechanism:
        val retainedFoo = nodeContext.getRetainedInstance(
            factory = { Foo(payload) },
            disposer = { it.cleanup() } // it: Foo
        )

        val view = YourNodeViewImpl()

        return YourNode(
            nodeContext = nodeContext,
            foo = retainedFoo, 
            view = view,
        )
    }
}