为什么不使用android导航组件工作后退按钮

Question

this my Auth Activity

class AuthActivity : AppCompatActivity() {
    private lateinit var navController: NavController
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding = ActivityAuthBinding.inflate(layoutInflater)
        setContentView(binding.root)

        navController = Navigation.findNavController(this, fragment.id)
        NavigationUI.setupActionBarWithNavController(this, navController)

    }

    override fun onSupportNavigateUp(): Boolean {
        return NavigationUI.navigateUp(navController, null)
    }

}

LoginFragment -> if login is success goto "AcceptCodeFragment"

 viewModel.loginResponse.observe(viewLifecycleOwner, { response ->
            viewBinding.pbLogin.visible(response is Resource.Loading)
            when (response) {
                is Resource.Success -> {
                    viewBinding.tvResponse.text = response.value.message
                    val action = LoginFragmentDirections.actionLoginFragmentToAcceptCodeFragment()
                    findNavController().navigate(action)
                }
                is Resource.Error -> if (response.isNetworkError) {
                    requireView().snackBar("Check your connection")
                } else {
                    requireView().snackBar(response.errorBody.toString())
                }
            }

in AcceptCodeFragment Back button not work.

Two fragments using same viewmodel.

Answer 1

Your issue is not with the back button not working, it is that LiveData is for state , not events like your loginResponse . As LiveData is for events, it redelivers the previous response when you go back to your LoginFragment . This then triggers your navigate() call again, pushing you right back to your AcceptCodeFragment .

As per the LiveData with SnackBar, Navigation, and other events blog post , LiveData cannot be directly used for events. Instead, you should consider using an event wrapper or another solution (such as a Kotlin Flow ) that allow your events to only be handled once.