Tiamat

Project Url: ComposeGears/Tiamat
Introduction: Simple Compose multiplatform navigation library
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Tiamat

Compose multiplatform navigation library

API

Add the dependency below to your module's build.gradle.kts file:

Module Version
tiamat Maven Central
tiamat-koin Maven Central

Multiplatform

sourceSets {
    commonMain.dependencies {
        // core library
        implementation("io.github.composegears:tiamat:$version")
        // Koin integration (https://github.com/InsertKoinIO/koin) 
        implementation("io.github.composegears:tiamat-koin:$version")
    }
}

Android / jvm

Use same dependencies in the dependencies { ... } section

Why Tiamat?

  • Code generation free
  • Pure compose
  • Support nested navigation
  • Support back-stack alteration (+deep-links)
  • Easy to use
  • Allow to pass ANY types as data, even lambdas (!under small condition)
  • Customizable transitions

Setup

1) Define your screens in one of 3 available ways:

  • chaotic good (screen name eq to value name)

      val Screen by navDestination<Unit> {
          // content
      }
    
  • chaotic neutral

    
      val Screen = NavDestination<Unit>("ScreenName") {
          // content
      }
    
  • chaotic evil

      object Screen : NavDestination<Unit> {
          override val name: String = "ScreenName"
    
          @Composable
          override fun NavDestinationScope<Unit>.Content() {
              // content
          }
    
      }
    

    2) Create navController

    val navController = rememberNavController(
       startDestination = Screen,
       destinations = arrayOf(
           Screen,
           AnotherScreen,
           // ...
       )
    )
    

    3) Setup navigation

    Navigation(navController)
    

    4) Navigate

    val Screen by navDestination<Unit> {
       val navController = navController()
       Column {
           Text("Screen")
           Button(onClick = { navController.navigate(AnotherScreen) }){
               Text("Navigate")
           }
       }
    }
    

see example: App.kt

Overview

Screen

The screens in Tiamat should be an entities (similar to composable functions)

the Args generic define the type of data, acceptable by screen as input parameters in the NavController:navigate fun

val RootScreen by navDestination<Unit> {
    // ...
    val nc = navController()
    // ...
    nc.navigate(DataScreen, DataScreenArgs(1))
    // ...
}

data class DataScreenArgs(val t: Int)

val DataScreen by navDestination<DataScreenArgs> {
    val args = navArgs()
}

The screen content scoped in NavDestinationScope<Args>

The scope provides a number of composable functions:

  • navController - provides current NavController to navigate back/further
  • navArgs - the arguments provided to this screen by NavControllr:navigate(screen, args) fun
  • navArgsOrNull - same as navArgs but provides null if there is no data passed or if it was lost
  • freeArgs - free type arguments, useful to store metadata or pass deeplink info
  • clearFreeArgs - clear free type arguments (eg: clear handled deeplink info)
  • navResult - provide the data passed to NavControllr:back(screen, navResult) as result
  • rememberViewModel - create or provide view model scoped(linked) to current screen

You may create NavController using one of rememberNavController functions:

fun rememberNavController(
    key: String? = null,
    storageMode: StorageMode? = null,
    startDestination: NavDestination<*>? = null,
    destinations: Array<NavDestination<*>>,
    onCreated: NavController.() -> Unit = {}
)

and display as part of any composable function

@Composable
fun Content() {
    val navController = rememberNavController( /*... */)
    Navigation(
        navController = navController,
        modifier = Modifier.fillMaxSize().systemBarsPadding()
    )
}

NavController will keep the screens data, view models, and states during navigation

[!IMPORTANT] The data may be cleared by system (eg: Android may clear memory)

Upon restoration state there is few cases depend on storageMode

Storage mode

  • null - will take parent NavController mode or ResetOnDataLoss for root controller
  • StorageMode.Savable - will store data in savable storage (eg: Android -> Bundle)

    [!IMPORTANT] Only 'Savable' types of params & args will be available to use

    eg: Android - Parcelable + any bundlable primitives

  • StorageMode.ResetOnDataLoss - store data in memory, allow to use any types of args & params (including lambdas). Reset nav controller upon data loss
  • StorageMode.IgnoreDataLoss - store data in memory, allow to use any types of args & params (including lambdas). Restore nav back stack, ignore data loss

Known limitations

[!IMPORTANT] Type checking has run into a recursive problem. Easiest workaround: specify types of your declarations explicitly ide error.

val SomeScreen1 by navDestination<Unit> {
  val navController = navController()
  Button(
      onClick = { navController.navigate(SomeScreen2) }, // << error here
      content = { Text("goScreen2") }
  )
}

val SomeScreen2 by navDestination<Unit> {
val navController = navController()
  Button(
      onClick = { navController.navigate(SomeScreen1) }, // << or here
      content = { Text("goScreen2") }
  )
}

Appears when it is circular initialization happen (Screen1 knows about Screen2 whot knows about Screen1 ...)

Solution: just define types of root(any in chain) screens explicitly

val SomeScreen1: NavDestination<Unit> by navDestination {  /* ... */ }

[!IMPORTANT] No data exception

Using storageMode = StorageMode.IgnoreDataLoss in the rememberNavController

Within screens val navArgs = navArgs()

May cause error in case internal data storage where cleared (eg: Android may release memory of activity)

Solution: there is safe version val navArgs = navArgsOrNull()

[!IMPORTANT] Why is my system back button works wired with custom back handler?

Using custom back handler do not forget 2 rules 1) Always place NavBackHandler before Navigation 2) use Navigation(handleSystemBackEvent = false) flag to disable extra back handler

Samples

Simple back and forward navigation:

1-simple-fb.webm

Bottom bar navigation:

2-bot-bar.webm

Passing data to next screen:

3-data-params.webm

Passing data to previous screen:

4-data-result.webm

Custom transition:

5-custom-transition.webm

Examples code

Hint

Multiplatform

I use startDestination = null + LaunchEffect \ DisposableEffect to make start destination dynamic and see 1 frame of animation

    // LaunchEffect & DisposableEffect are executed on `next` frame, so you may see 1 frame of animation
    // to avoid this effect use `onCreated` lambda within `rememberNavController` fun
    // see DeeplinkScreen.kt

    val deeplinkNavController = rememberNavController(
        key = "deeplinkNavController",
        startDestination = ShopScreen,
        destinations = arrayOf(ShopScreen, CategoryScreen, DetailScreen)
    ) { // executed right after being created or restored
        // we can do nav actions before 1st screen bing draw without seeing 1st frame
        if (deeplink != null) {
            editBackStack {
                clear()
                add(ShopScreen)
                add(CategoryScreen, deeplink.categoryId)
            }
            replace(
                dest = DetailScreen,
                navArgs = DetailParams(deeplink.productName, deeplink.productId),
                transition = navigationNone()
            )
            clearFreeArgs()
        }
    }

Desktop

There is no default 'back' action on desktop

If you want to add one into the Tiamat navigation just use the code below:

fun main() = application {
    val backHandler = LocalNavBackHandler.current // < get ref to Global back handler
    Window(
        // ...
        onKeyEvent = { // < add global key event handler
           it.key == Key.Escape && it.type == KeyEventType.KeyUp && backHandler.back() // < call backHandler.back()
        },
        // ...
    ) {
        App()
    }
}

Android

Tiamat-android overrides LocalLifecycleOwner for each destination and compatible with lifecycle-aware components

See an example of camera usage: AndroidViewLifecycleExample.kt

iOS

Nothing specific (yet)

Run/Build sample

Android: ./gradlew example:composeApp:assembleDebug

Desktop: ./gradlew example:composeApp:run

iOS: run XCode project or else use KMM plugin iOS target

License

Developed by ComposeGears 2024

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
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