Recyclerview 0 children, can't test viewholder click

[JustinTullgren]

Description

Calling notifyDataSetChanged() and calling ActivityController.visible() does not update the recyclerview childcount or returns null for recycler.findViewHolderForAdapterPosition(0)

I tried follow steps in this Stackoverflow post which mentioned the visible method. The other results didn't work either.

The activity works and loads fine.

I am not sure its a bug or just a misunderstanding on my part. I tried looking at the github samples and articles on line but they all had similar answers (draw the recycler manually) or were very shallow.

Steps to Reproduce: Code below(modified to not show domain details)

Activity

class TheActivity : BaseActivity<IView, IPresenter>(), IView {

	private val theAdapter = TheAdapter { presenter.select(it) }
	@Inject lateinit var presenter: IPresenter

	override fun onInject() {
		component?.inject(this)
	}

	override fun getIPresenter(): IPresenter = presenter
	override fun getIView(): IView = this

	override fun onCreate(savedInstanceState: Bundle?) {
		super.onCreate(savedInstanceState)
		setContentView(R.layout.activity_example)
		with(activity_example_recyclerview) {
			adapter = theAdapter
			layoutManager = LinearLayoutManager(this@TheActivity)
		}

	}

	override fun setItems(items: List<String>) {
		theAdapter.setItems(items)
	}

	private class ViewHolder(itemView: View) : RecyclerView.ViewHolder(itemView)

	private class TheAdapter(private val itemClick: (String) -> Unit) : RecyclerView.Adapter<ViewHolder>() {
		private var list = listOf<String>()
		fun setItems(list: List<String>) {
			this.list = list
			notifyDataSetChanged()
		}
		override fun onBindViewHolder(holder: ViewHolder, position: Int) {
			val item = list[position]
			holder.itemView.setOnClickListener { itemClick(item) }
			val text = holder.itemView as TextView
			text.text = item
		}

		override fun getItemCount(): Int = list.size

		override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder = ViewHolder(TextView(parent.context))
	}
}

Test

@RunWith(RobolectricTestRunner::class)
class TheActivityUnitTest {
	private lateinit var subject:TheActivity
	private val controller = Robolectric.buildActivity(TheActivity::class.java)
	private val mockExistingItems = listOf("foo", "bar", "baz")
	private val mockPresenter = mock<IPresenter>()
	private val mockComponent = mock<AppCompatActivityComponent> {
		on { inject(any<TheActivity>()) }.doAnswer {
			with(it.arguments[0] as TheActivity) {
				presenter = mockPresenter
			}
			return@doAnswer null
		}
	}

	@Before
	fun setup() {
		subject = controller.get()
		subject.component = mockComponent
	}

	@Test
	fun selectItemFromList() {
		controller.create().start().visible()
		subject.setItems(mockExistingItems) // Invokes notifyDataSetChanged()
		controller.visible()
		subject.findViewById<RecyclerView>(R.id.activity_example_recyclerview)
				.findViewHolderForItemId(0)
				// THIS WILL FAIL as findViewHolderForItemId returns null
				.itemView
				.performClick()
		// OR Alternatively 
		/*
		subject.findViewById<RecyclerView>(R.id.activity_example_recyclerview)
				.findViewHolderForAdapterPosition(0)
				.itemView
				.performClick()
		 */
		
		// OR Alternatively 
		/*
		subject.findViewById<RecyclerView>(R.id.activity_example_recyclerview)
				.getChildAt(0)
				.performClick()
		 */
		verify(mockPresenter).select(mockExistingItems[0])
	}
}

Robolectric & Android Version

Robolectric: 3.6.1
Android compileSdkVersion: 26,
android minSdkVersion : 21,
android targetSdkVersion : 26

[JustinTullgren]

Doing the measure manually fixed the issue. It would still be nice if this was not required.

val recycler = subject.findViewById<RecyclerView>(R.id.activity_example_recyclerview)
recycler.measure(0,0)
recycler.layout(0,0,100,1000)

[amrfarid140]

Getting the same issue on Robolectric 4.1, @JustinTullgren suggested solution works.

[brettchabot]

I'm hoping this issue will be fixed by the fix for #4153 which I've been working on.

Robolectric currently performs layout assuming the window is zero-size, which leads to a bunch of inconsistencies when sizing TextViews, RecyclerViews etc.

[lupsyn]

Same issue on Roboelectric 4.2

[PaulKlauser]

Still seeing this issue on Robolectric 4.3.1

[calvarez-ov]

Just calling recycler.measure(0,0) was enough to fix the issue in my case.

[bhuva13]

Just calling recycler.measure(0,0) was enough to fix the issue in my case.

What is the Robolectric version you are using?

[mnlin0905]

@bhuva13 @PaulKlauser @lupsyn

This is how I handle it here

testImplementation "org.robolectric:robolectric:4.5.1"
testImplementation 'androidx.test.espresso:espresso-core:3.3.0'

test code

   @Test
    fun `should show all buttons and digit text content is empty when launch OplusDialpadFragment with open screen`() {
        // GIVEN
        val screenWidth = 1080
        val screenHeight = 1920

        // Manually load the soft keyboard interface into the activity
        activityRule.scenario.onActivity {
            it.supportFragmentManager
                .beginTransaction()
                .add(R.id.vp_screen_center, OplusDialpadFragment(), OplusDialpadFragment::class.simpleName)
                .commitNow()
        }

        // WHEN
        activityRule.scenario.onActivity {
            it.supportFragmentManager
                .findFragmentByTag(OplusDialpadFragment::class.simpleName)
                ?.view
                ?.findViewById<RecyclerView>(R.id.rv_dialpad_buttons)
                ?.run {
                    measure(
                        makeMeasureSpec(screenWidth, View.MeasureSpec.EXACTLY),
                        makeMeasureSpec(screenHeight, View.MeasureSpec.AT_MOST),
                    )
                    layout(0, 0, screenWidth, screenHeight)
                }
        }

        Shadows.shadowOf(Looper.getMainLooper()).idle()

        // THEN
        for ((number, _) in (DialpadViewModel.DIALPAD_NUMBERS_LETTERS)) {
            onView(withText(number.toString())).check(matches(isEnabled()))
        }
    }

The key code is here

measure(
      makeMeasureSpec(screenWidth, View.MeasureSpec.EXACTLY),
      makeMeasureSpec(screenHeight, View.MeasureSpec.AT_MOST),
  )
  layout(0, 0, screenWidth, screenHeight)

Finally ensure that the test cases can cover the source code

[mnlin0905]

@JustinTullgren

Perhaps, you can refer to this article

Robolectric Tips: Testing RecyclerViews