Android Espresso: ViewPager does not have adapter instance

Question

I´m using in my Android (4.0+) app fragment (in Activity) with Tab bar.

I want to create Espresso test but if I create main Activity and open the fragment. I get this Exception:

java.lang.IllegalStateException: ViewPager does not have adapter instance.
at com.astuetz.PagerSlidingTabStrip.setViewPager(PagerSlidingTabStrip.java:177)
at cz.villamemories.detoxme.staticcontent.StaticContentFragment.onCreateView(StaticContentFragment.java:197)

My code in fragment:

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

        mViewPagerAdapter = new StaticContentPagerAdapter(
                this.getChildFragmentManager(), mItemsList, categories);

        mPager.setAdapter(mViewPagerAdapter);

        mTabs.setViewPager(mPager); //line 197

Do you have some tip where can be a problem? What is wrong?

Answer 1

I was also facing the issue with ViewPager in fragment. This problem occurs me because of my viewpager has a multiple root elements.

@RunWith(JUnit4.class)
public class FragmentTest {

private static final String TAG = "FragmentTest";

@Rule
public ActivityTestRule<MainActivity> mActivity = new ActivityTestRule<MainActivity>(MainActivity.class);

@Test
public void checkTabSwiping() {
    onView(nthChildOf(withId(R.id.main_content), 5)).check(matches(withId(R.id.homecontentgrouppager)));
}

public static Matcher<View> firstChildOf(final Matcher<View> parentMatcher) {
    return new TypeSafeMatcher<View>() {
        @Override
        public void describeTo(Description description) {
            description.appendText("with first child view of type parentMatcher");
        }

        @Override
        public boolean matchesSafely(View view) {

            if (!(view.getParent() instanceof ViewGroup)) {
                return parentMatcher.matches(view.getParent());
            }
            ViewGroup group = (ViewGroup) view.getParent();
            return parentMatcher.matches(view.getParent()) && group.getChildAt(0).equals(view);

        }
    };
}
public static Matcher<View> nthChildOf(final Matcher<View> parentMatcher,
                                       final int childPosition){
    return new TypeSafeMatcher<View>() {
        @Override
        public void describeTo(Description description) {
            description.appendText("with " + childPosition + " child view of type parentMatcher");
        }

        @Override
        public boolean matchesSafely(View view) {
            if (!(view.getParent() instanceof ViewGroup)) {
                return parentMatcher.matches(view.getParent());
            }

            ViewGroup group = (ViewGroup) view.getParent();
            return parentMatcher.matches(view.getParent()) && view.equals(group.getChildAt(childPosition));
        }
    };
}
}

and this is my homefragment.xml file

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:animateLayoutChanges="true"
android:background="@color/black"
android:orientation="vertical">

<android.support.v4.view.ViewPager
    android:id="@+id/promotionalviewpager"
    android:layout_width="match_parent"
    android:layout_height="match_parent"></android.support.v4.view.ViewPager>

<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="@dimen/size_5"
    android:gravity="center_horizontal">

    <LinearLayout
        android:id="@+id/viewPagerCountDots"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:gravity="center_horizontal"
        android:orientation="horizontal" />

</RelativeLayout>

I hope it may help you to create a test case in Expresso Framework.