Navigation

Environment

dependencies {
...
  def nav_version = "2.3.5"

  // Kotlin
  implementation("androidx.navigation:navigation-fragment-ktx:$nav_version")
  implementation("androidx.navigation:navigation-ui-ktx:$nav_version")
}

Create a navigation graph

• (optional) Create ‘navigation-res-directory’ into ‘res’ directory.
• Create navigation graph res file(e.g. name : nav_graph) into ‘navigation-res-directory’.
• Open nav_graph.xml. Click ‘new destination icon(+)’ for add all fragments what has created for destination target.
• Connect arrow between destinations.
• (optional) Change label attribute.

Add navigation graph in activity

• Open ‘activity.xml’ and on design mode, search ‘NavHostFragment’ view

  and drag & drop into activity design board.

Navigate

class MainFragment : Fragment(){
...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        button.setOnClickListener {
            findNavController().navigate(R.id.action_mainFragment_to_secondFragment)
        }
    }
}

Update Action bar

import androidx.navigation.findNavController
import androidx.navigation.fragment.NavHostFragment
import androidx.navigation.ui.AppBarConfiguration
import androidx.navigation.ui.navigateUp
import androidx.navigation.ui.setupActionBarWithNavController

class MainActivity .. {
...
	private lateinit var appBarConfiguration: AppBarConfiguration

...
	override fun onCreate(savedInstanceState: Bundle?) {
    ...

    	val navHostFragment =
        	supportFragmentManager.findFragmentById(R.id.nav_host_fragment) as 				NavHostFragment
    	val navController = navHostFragment.navController
    	appBarConfiguration = AppBarConfiguration(navController.graph)
    	setupActionBarWithNavController(navController, appBarConfiguration)
	}
	
	override fun onSupportNavigateUp(): Boolean {
    	val navController = findNavController(R.id.nav_host_fragment)
    	return navController.navigateUp(appBarConfiguration)
        	    || super.onSupportNavigateUp()
	}

...
}


//import 타겟 주소가 여러개인 경우가 있어 주의.

Pass data between destinations

• Open ‘nav_graph.xml’.
• Click receiving destination and add arguments(enter name/type).

(Do ‘Build > rebuild’ for well reflecting.)

1. Ensure type-safety by using Safe Args

buildscript {
    repositories {
        google()
    }
    dependencies {
        val nav_version = "2.3.5"
        classpath("androidx.navigation:navigation-safe-args-gradle-plugin:$nav_version")
    }
}


//top level build.gradle

plugins {
    id("androidx.navigation.safeargs")
}


//module's build.gradle

2. Posting destination

class MainFragment : Fragment() {
  ...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        button.setOnClickListener {
            val action = MainFragmentDirections
            .actionMainFragmentToSecondFragment("Hi")
            findNavController().navigate(action)
        }
    }
}

3. Receiving destination

class SecondFragment : Fragment() {
    val args : SecondFragmentArgs by navArgs()
...
    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        textView.text = args.text
    }
}