CircleImageView变成正方形

Question

我有一个CirceImageView如下

<de.hdodenhof.circleimageview.CircleImageView
    android:id="@+id/circleImageView_right_arrow"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/ic_keyboard_arrow_right"
    android:layout_marginLeft="20dp"
    android:layout_marginStart="20dp"
    android:background="@drawable/imageview_border"
    android:clickable="true"
    android:focusable="true"/>

imageview_border.xml如下

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <!--<stroke
        android:width="5dp"
        android:color="@color/light_green" />-->
    <corners
        android:radius="1000dp"   >
    </corners>
    <!--<solid
        android:color="@color/light_green">
    </solid>-->
</shape>

当我在CircleImageView上应用动画时，视图变成一个正方形。为什么会发生这种情况，如何避免将其变成正方形？

int colorFrom = getResources().getColor(R.color.light_green); // The color to change from
int colorTo = getResources().getColor(R.color.colorPrimary); // The color to change to
ValueAnimator colorAnimation = ValueAnimator.ofObject(new ArgbEvaluator(), colorFrom, colorTo);
        colorAnimation.setDuration(1000); // milliseconds
        colorAnimation.setRepeatCount(-1); // INFINITE
        colorAnimation.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {

            @Override
            public void onAnimationUpdate(ValueAnimator animator) {
                mRightArrowCircleImageView.setBackgroundColor((int) animator.getAnimatedValue());
            }
        });
        colorAnimation.start();