在 Kotlin 中使用 safeArgs 进行导航抛出和错误

Question

I have a fragment that can be either navigated to via a bottom navBar without arguments or from a different fragment with arguments. The navigation itself works perfectly fine but as soon as I add my arguments it crashes.

I'm unsure how much code is needed, so sorry if it's not complete:

This is my navigation fragment:

<navigation xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/navigation"
app:startDestination="@id/homeFragment">

<fragment
    android:id="@+id/homeFragment"
    android:name="fh.wfp2.flatlife.ui.views.HomeFragment"
    android:label="Flatlife"
    tools:layout="@layout/home_fragment" />
<fragment
    android:id="@+id/todoFragment"
    android:name="fh.wfp2.flatlife.ui.views.TodoFragment"
    android:label="Todos">
    <action
        android:id="@+id/action_todoFragment_to_addTodoFragment"
        app:destination="@id/addTodoFragment" />
    <argument
        android:name="taskname"
        app:argType="string" />
    <argument
        android:name="isImportant"
        app:argType="boolean" />
</fragment>
<fragment
    android:id="@+id/addTodoFragment"
    android:name="fh.wfp2.flatlife.ui.views.AddTodoFragment"
    android:label="AddTodoFragment">
    <action
        android:id="@+id/action_addTodoFragment_to_todoFragment"
        app:destination="@id/todoFragment" />


</fragment>
</navigation>

This is my addTodoFragment :

class AddTodoFragment : Fragment(R.layout.add_task_fragment) {

private lateinit var binding: AddTaskFragmentBinding

override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
    super.onViewCreated(view, savedInstanceState)
 
    binding = AddTaskFragmentBinding.bind(view)
    binding.bAddTodo.setOnClickListener {
        if (binding.etAddTodo.text.isNotEmpty()) {
           // viewModel.onAddTodoClicked(binding.etAddTodo.text.toString(), 
binding.cbImportant.isChecked)
           findNavController().navigate(
                AddTodoFragmentDirections.actionAddTodoFragmentToTodoFragment(
                    binding.etAddTodo.text.toString(), binding.cbImportant.isChecked
                )
            )
        } else {
            Snackbar.make(it, "The task field can't be empty", Snackbar.LENGTH_SHORT).show()
            
        }
    }

}
}

This is how I'm trying to get the arguments in TodoFragment .

private val args: TodoFragmentArgs by navArgs()
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
//setting binding and other onClickListeners but they work fine

//reading args
//this i thought would work because then args only get read if not null
args?.let { //debugger stops here and app crashes
        if(args.taskname.isNotEmpty())
        viewModel.onAddTodoClick(Todo(name = args.taskname, isImportant = args.isImportant))
    }

/*second try which I took directly from developers.android but which doesn't make sense in my case i 
think because the args could be null I guess

val todoName = args.taskname
    val isImportant = args.isImportant
    viewModel.onAddTodoClick(Todo(name = todoName, isImportant = isImportant))
*/

}

This is the error message i get:

I hope it is clear what I mean, otherwise, I'll update the question. It'll probably be something simple but I can't quite put my finger on it.

Answer 1

val args = arguments?.let {
    SecondFragmentArgs.fromBundle(
        it
    )
}
if (args != null) {
    firstDataList = args.taskName
    secondDataList = args.isImportant
}

This is how the receiving fragment code should look like. This should work.

Answer 2

So credit to @Onik for the idea to leave SafeArgs away. I needed to dump the SafeArgs class call for receiving the arguments and it looks like this now. This is definitely not the cleanest way I guess but I don't know yet why the SafeArgs call doesn't work and I'm too new to Kotlin to write the following code in a cleaner way. But it works, for now.

arguments?.let {
        var myArg1: String? = null
        var myArg2: Boolean
        arguments?.getString("argument1")?.let { arg1->
            myArg1= arg1
        }
        arguments?.getBoolean("argument2")?.let { arg2->
            myArg2= arg2

            if (myArg1!= null)
                //do logis with args
        }

    }