Android-Espresso: How check TextView is center horizontally?

Issue

Here my xml:

<TextView
            android:id="@+id/loginTextView"
            android:layout_width="255dp"
            android:layout_height="60dp"
            android:layout_marginBottom="15dp"
            android:background="@drawable/sign_in_login_bg"
            android:gravity="center"
            android:onClick="@{ () -> presenter.doLogin()}"
            android:text="@string/login"
            android:textAllCaps="true"
            android:textColor="@android:color/white"
            app:layout_constraintBottom_toTopOf="@+id/registerTextView"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent" />

        <TextView
            android:id="@+id/registerTextView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginBottom="15dp"
            android:onClick="@{ () -> presenter.doRegister()}"
            android:text="@string/register"
            android:textAllCaps="true"
            android:textColor="@color/color_primary"
            android:textSize="13sp"
            android:textStyle="bold"
            app:layout_constraintBottom_toTopOf="@+id/forgotPasswordTextView"
            app:layout_constraintEnd_toEndOf="@+id/loginTextView"
            app:layout_constraintStart_toStartOf="@+id/loginTextView" /

Because I use app:layout_constraintEnd_toEndOf="@+id/loginTextView" and app:layout_constraintStart_toStartOf="@+id/loginTextView" the registerTextView is center horizontally.

And now I want to write Espresso test check that registerTextView is on center horizontally? How I can do this?

Solution

All you have to do is to retrieve the display size and make sure the left coordinate of the view equals to the distance between a right view coordinate and a right display one. So, you could create a matcher like:

private static Matcher<View> isCenteredHorizontally() {
    return new TypeSafeMatcher<View>() {
        @Override
        protected boolean matchesSafely(View item) {
            WindowManager windowManager = (WindowManager) item.getContext().getSystemService(Context.WINDOW_SERVICE);                  
            Display display = windowManager.getDefaultDisplay(); 
            Point displaySize = new Point(); 
            display.getSize(displaySize); 
            int width = displaySize.x + 1; 

            int[] outLocation = new int[2]; 
            item.getLocationOnScreen(outLocation); 
            int viewLeft = outLocation[0]; 
            int rightMargin = width - (viewLeft + item.getMeasuredWidth()); 
            // if screen width is an even number and view width an odd one then an error is 1 point
            return Math.abs(rightMargin - viewLeft) < 2;
        }

        @Override
        public void describeTo(Description description) {

        }
    };
}

And then use it as:

onView(withId(R.id.registerTextView)).check(matches(isCenteredHorizontally()));

Answered By - Anatolii