IssueTracker

As a workaround, your Fragment can set the arguments to an empty Bundle if it is null:

if (arguments == null) {
  arguments = Bundle()
}
// Assuming myArgs is set via by navArgs()
val myArg = myArgs.myArg

Project: platform/frameworks/support
Branch: androidx-master-dev

commit d8c9982a9cac54247134252eea8d8a4cbf757e74
Author: Ian Lake <ilake@google.com>
Date:   Fri Mar 15 13:21:12 2019

    Avoid sending a null Bundle when NavArguments are present
   
    When using arguments with android:defaultValue="@null",
    these attributes are dropped by XmlPullParser, so the
    NavArgument does not have a default value set. Change
    addInDefaultArgs() to always return a non-null Bundle
    if there are NavArguments set at all to ensure that
    Safe Args can correctly parse the empty Bundle and
    fill in the correct default values.
   
    This also simplifies the process if you're not using
    Safe Args since you can requireArguments() and the
    proper gets with your default values.
   
    Test: new AddInDefaultArgsTest parameterized test
    Fixes: 128531879
    Change-Id: I6ec9673100790df03b5aa1d86f74dbec70173095

A       navigation/common/src/androidTest/java/androidx/navigation/AddInDefaultArgsTest.kt
M       navigation/common/src/main/java/androidx/navigation/NavDestination.java

https://android-review.googlesource.com/930456
https://goto.google.com/android-sha1/d8c9982a9cac54247134252eea8d8a4cbf757e74

We've fixed this for Navigation 2.1.0-alpha01 at the library level, rather than only in Safe Args. Destinations with any argument will have a non-null Bundle.

I'm still getting the error with "androidx.navigation:navigation-safe-args-gradle-plugin:2.1.0-alpha02"

<argument
                        android:name="filter"
                        android:defaultValue="@null"
                        app:nullable="true"
                        app:argType="***.ConsultationsFilter"
                        />
---------
class TestFragment : androidx.fragment.app.Fragment() {
    private val args by navArgs<TestFragment>()
...
override fun onCreateView(
        inflater: LayoutInflater, container: ViewGroup?,
        savedInstanceState: Bundle?
    ): View? {
....
   val filter = args.filter // <-- throws null argument exception
}

upd line: private val args by navArgs<TestFragmentArg>()