Navigation Component - All the best practices

Navigation Component Implementations  

Conditional Navigation 

• When we conditionally navigate to different fragments based upon a certain conditions. 
• Example. Navigate to HomeFragment when user is logged in otherwise navigate to LoginFragment. 

Back Stack Manipulation 

• Navigation Controller handles the back stack for us. What this means is when we navigate to a destination, it's automatically adding each destination to the back stack. 
• The navigation action can manipulate the back stack as it moves to the next destination. 
• Sometimes we need actions pop destinations off of the back stack according to our logical conditions for this we use the pop behaviour attributes from the editor. 
• PopUpTo : desired fragment and select inclusive true, It tells the navigation component to pop FragmentTransaction over the fragment back stack until it finds the one that returns the desired fragment.  
• apppopUpToInclusive="true" will clear the back stack and let you exit. 

Adding Up Button in Action Bar using Navigation Controller 

• The Navigation Controller has a UI library called navigation UI 
• It integrates with the Action Bar to implement the correct behaviour for the Up button. 
• To hook up the button to navigation, navigation UI needs access to the navigation controller. 
• The preferred way of finding the Navigation Controller in an activity is to use the findNavController method that takes the activity in the NavHostFragment parameters.  

Use case :

• First find the navController from your navigation host fragment 
• Link the navController to our Action Bar 
• use Ctrl+ O in Android Studio to override any methods 
• override onSupportNavigateUp(), here we find the navController and call navigateUp 

// find the navController from your navigation host fragment
val navController = this.findNavController(R.id.navigationHost)
// link the navController to our action bar
NavigationUI.setupActionBarWithNavController(this, navController)

override fun onSupportNavigateUp(): Boolean {
    val navController = this.findNavController(R.id.navigationHost)
    return navController.navigateUp()
}

Adding Menu 

Menus are created from menu XML resources. 

Use Case: 

• Create a new menu resource file 
• Add menu item 
• Call setHasOptionsMenu(true) : this tells Android that our fragment has an Options Menu 
• Note: if you add menu to the container activity, it is displayed every fragment that it contains, so if you set the menu to fragment it is displayed to particular fragment only. 
• override onCreateOptionsMenu and inflate menu resource 
• override onOptionsItemSelected and call onOptionsItemSelected to connect to our NavigationUI 

override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
    super.onCreateOptionsMenu(menu, inflater)
    inflater?.inflate(R.menu.overflow_menu, menu)
}

override fun onOptionsItemSelected(item: MenuItem): Boolean {
    return NavigationUI.onNavDestinationSelected(item!!, 
        view!!.findNavController()) 
            ||super.onOptionsItemSelected(item)
}