Quick start guide¶

You can check out Composable navigation, which explains the concepts you'll encounter in this guide.

The scope of this guide¶

The steps below will cover:

Integrating Appyx into your project
Creating a very simple Node hierarchy
We'll use a simple back stack for navigation
We'll see how to change transition animations easily

This should be enough to get you started as a rudimentary application structure.

1. Add Appyx to your project¶

Please refer to the Downloads to find the relevant artifacts (also depending on whether you're doing this in a multiplatform project or not).

For the scope of this quick start guide, you will need to add dependencies for:

2. Create a root Node¶

class RootNode(
    nodeContext: NodeContext
) : LeafNode(
    nodeContext = nodeContext
) {
    @Composable
    override fun Content(modifier: Modifier) {
        Text("Hello world!")
    }
}

3. Connect to your platform¶

Plug your root node into your platform: Multiplatform | Node hosts.

Use the multiplatform imports Appyx provides in any of the code snippets from now on, such as:

import com.bumble.appyx.utils.multiplatform.Parcelable
import com.bumble.appyx.utils.multiplatform.Parcelize
import com.bumble.appyx.utils.multiplatform.RawValue

4. Define children¶

A single leaf node isn't all that interesting. Let's add some children to the root!

First, let's define the possible set of children using a sealed class. We'll refer them via these navigation targets:

import com.bumble.appyx.utils.multiplatform.Parcelable
import com.bumble.appyx.utils.multiplatform.Parcelize

/**
 * You can create this class inside the body of RootNode
 * 
 * Note: You must apply the 'kotlin-parcelize' plugin to use @Parcelize
 * https://developer.android.com/kotlin/parcelize
 */
sealed class NavTarget : Parcelable {
    @Parcelize
    object Child1 : NavTarget()

    @Parcelize
    object Child2 : NavTarget()

    @Parcelize
    object Child3 : NavTarget()
}

Next, let's modify RootNode so it extends Node instead of LeafNode:

class RootNode(
    nodeContext: NodeContext
) : Node<NavTarget>(
    appyxComponent = TODO("We will come back to this in Step 5"),
    nodeContext = nodeContext
) {

Node expects us to implement the abstract method buildChildNode. This is how we relate navigation targets to actual children. Let's use these helper methods to define some placeholders for the time being – we'll soon make them more appealing:

override fun buildChildNode(reference: NavTarget, nodeContext: NodeContext): Node =
    when (reference) {
        NavTarget.Child1 -> node(nodeContext) { Text(text = "Placeholder for child 1") }
        NavTarget.Child2 -> node(nodeContext) { Text(text = "Placeholder for child 2") } 
        NavTarget.Child3 -> node(nodeContext) { Text(text = "Placeholder for child 3") }
    }

Great! With this mapping created, we can now just refer to children using the sealed class elements, and Appyx will be able to relate them to other nodes.

5. Add a back stack¶

The project wouldn't compile just yet. Node expects us to pass an instance of an AppyxComponent – the main control structure in any case when we want to add children. No need to worry now – for simplicity, let's just go with a simple BackStack implementation here:

class RootNode(
    nodeContext: NodeContext,
    private val backStack: BackStack<NavTarget> = BackStack(
        model = BackStackModel(
            initialTarget = NavTarget.Child1,
            savedStateMap = nodeContext.savedStateMap,        
        ),
        visualisation = { BackStackFader(it) }
    )
) : Node<NavTarget>(
    nodeContext = nodeContext,
    appyxComponent = backStack // pass it here
) {

With this simple addition we've immediately gained a lot of power! Now we can use the back stack's API to add, replace, pop children with operations like:

backStack.push(NavTarget.Child2)    // will add a new navigation target to the end of the stack and make it active 
backStack.replace(NavTarget.Child3) // will replace the currently active child
backStack.pop()                     // will remove the currently active child and restore the one before it

Since we passed the back stack to the Node, all such changes will be immediately reflected. We only need to add it to the composition:

@Composable
override fun Content(modifier: Modifier) {
    Column(
        modifier = modifier
    ) {
        // Let's include the elements of our component into the composition
        AppyxNavigationContainer(
            appyxComponent = backStack,
            modifier = Modifier.weight(0.9f)
        )

        // Let's also add some controls so we can test it
        Row(
            horizontalArrangement = Arrangement.Center,
            modifier = Modifier
                .fillMaxWidth()
                .weight(0.1f)
        ) {
            TextButton(onClick = { backStack.push(NavTarget.Child1) }) {
                Text(text = "Push child 1")
            }
            TextButton(onClick = { backStack.push(NavTarget.Child2) }) {
                Text(text = "Push child 2")
            }
            TextButton(onClick = { backStack.push(NavTarget.Child3) }) {
                Text(text = "Push child 3")
            }
            TextButton(onClick = { backStack.pop() }) {
                Text(text = "Pop")
            }
        }
    }
}

6. Visualisations, transitions¶

Adding a different visual representation of our model and its state changes is as simple as changing this:

visualisation = { BackStackFader(it) }

to this:

visualisation = { BackStackSlider(it) }

or this:

visualisation = { BackStackParallax(it) }

or this:

visualisation = { BackStack3D(it) }

Be sure to check the Back stack documentation where you can also find live previews of the above visualisations.

Need something more custom?

You can create your own visualisations.
Instead of a back stack, you can also find other Components in the library, or you can create your own.

7. Proper child nodes¶

As a last step, let's replace at least one of the child placeholders with another proper node.

Let's create a dedicated class:

class SomeChildNode(
    nodeContext: NodeContext
) : LeafNode(
    nodeContext = nodeContext
) {
    @Composable
    override fun Content(modifier: Modifier) {
        Text("This is SomeChildNode")
    }
}

Now we can update the buildChildNode method in RootNode so that the target Child3 refers to this node. It should work out of the box:

override fun buildChildNode(reference: NavTarget, nodeContext: NodeContext): Node =
    when (reference) {
        NavTarget.Child1 -> node(nodeContext) { Text(text = "Placeholder for child 1") }
        NavTarget.Child2 -> node(nodeContext) { Text(text = "Placeholder for child 2") } 
        NavTarget.Child3 -> SomeChildNode(nodeContext)
    }

What's next?¶

Congrats, you've just built your first Appyx tree!

You can repeat the same pattern and make any embedded children also a Node with their own children, navigation models, and transitions. As complexity grows, generally you would:

Have a LeafNode
At some point make it a Node and add children to it
At some point extract the increasing complexity from a placeholder to another LeafNode
Repeat the same on children, go to 1.