Android UI testing, what is the alternative for deprecated ViewAsserts assertHorizontalCenterAligned?

Issue

In Android UI testing we had the ViewAsserts class which is deprecated in API level 24.

The class had some methods such as assertHorizontalCenterAligned to test if a view is horizontally centered within another view.

What is the alternative for such a method in the new Espresso PositionAssertions?

It has Assertions for left,right,top and bottom alignment, but no center assertions.

Solution

To begin, my answer doesn't use PositionAssertions, but you said it is okay

I created my a custom ViewAsserts, and it works on any Android platform

Your view

Let's say you have the folowing xml view

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/activity_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"

    tools:context="merchantapp.ul.com.myapplication.MainActivity">

    <RelativeLayout
        android:id="@+id/ll"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <LinearLayout
            android:id="@+id/lll"
            android:layout_width="20dp"
            android:layout_height="20dp"
            android:layout_centerInParent="true"
            android:orientation="vertical"></LinearLayout>
    </RelativeLayout>
</RelativeLayout>

The view with id lll is in the center of the view with id ll

Custom ViewAsserts

Create class HorizontalViewAssertion

public class HorizontalViewAssertion extends TypeSafeMatcher<View> {
    private final View view;

    private HorizontalViewAssertion (View view) {
        this.view = view;
    }


    public static HorizontalViewAssertion alignHorizantalWith(View view) {
        return new HorizontalViewAssertion(view);
    }

    @Override
    protected boolean matchesSafely(View item) {

        float centerX1 = item.getX() + (((float)item.getWidth())/2.0f);
        float centerX2 = this.view.getX() + (((float)this.view.getWidth())/2.0f);
        if ( (Math.abs(centerX1 - centerX2)) <= 1)
            return  true;
        return false;
    }

    @Override
    public void describeTo(Description description) {

    }
}

Your test unit

Create your test unit

@RunWith(AndroidJUnit4.class)
public class ExampleInstrumentedTest {

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

    @Test
    public void testHorizantalCenter() {
        onView(withId(R.id.lll)).check(ViewAssertions.matches(alignHorizantalWith(mActivityRule.getActivity().findViewById(R.id.ll))));
    }
}

The test will pass

Description

The idea is simple, we have two views, let's call them view1 and view2

Calculate the horizontal x for the center of both views by getting the x axis and summing it to half of the width

Then check if these two centers are the same (Well, I am not checking if they are equal, but I am checking if the difference between them is less than 1 and that's because of dividing in the floating point. From math point of view, the difference will never more than 0.5)

I hope that's good for you

Answered By - William Kinaan