Como deixar uma imagem circular no Android

dependencies { ... compile 'de.hdodenhof:circleimageview:2.1.0' }

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="wrap_content">
<ImageView android:layout_width="64dp" android:layout_height="64dp" android:src="@drawable/person" android:id="@+id/item_foto"/>
<LinearLayout android:layout_width="wrap_content" android:layout_height="match_parent" android:orientation="vertical" android:gravity="center_vertical">
<TextView <!-- atributos -->/>
<TextView <!-- atributos -->/>
</LinearLayout>
</LinearLayout>

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="horizontal" android:layout_width="match_parent" android:layout_height="wrap_content">
<de.hdodenhof.circleimageview.CircleImageView android:layout_width="64dp" android:layout_height="64dp" android:src="@drawable/person" android:id="@+id/item_foto"/>
<LinearLayout android:layout_width="wrap_content" android:layout_height="match_parent" android:orientation="vertical" android:gravity="center_vertical">
<TextView <!-- atributos -->/>
<TextView <!-- atributos -->/>
</LinearLayout>
</LinearLayout>

import de.hdodenhof.circleimageview.CircleImageView;
public class AlunosAdapter extends BaseAdapter {
// atributos e métodos
@Override public View getView(int position, View convertView, ViewGroup parent) { 
    Aluno aluno = alunos.get(position);
LayoutInflater inflater = LayoutInflater.from(context);
View view = convertView; if (view == null) { 
    view = inflater.inflate(R.layout.list_item, parent, false); 
    }
// restante do código
CircleImageView campoFoto = (CircleImageView) view.findViewById(R.id.item_foto);
String caminhoFoto = aluno.getCaminhoFoto(); 
    if (caminhoFoto != null) {
         Bitmap bitmap = BitmapFactory.decodeFile(caminhoFoto); 
         Bitmap bitmapReduzido = Bitmap.createScaledBitmap(bitmap, 100, 100, true); campoFoto.setImageBitmap(bitmapReduzido);
        campoFoto.setScaleType(ImageView.ScaleType.FIT_XY); }
return view; } 
}

<de.hdodenhof.circleimageview.CircleImageView android:id="@+id/item_foto" android:layout_width="64dp" android:layout_height="64dp" android:padding="5dp" android:src="@drawable/person" />

 E/UncaughtException: java.lang.ClassCastException: android.support.v7.widget.AppCompatImageView cannot be cast to de.hdodenhof.circleimageview.CircleImageView

<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="horizontal">
<ImageView android:id="@+id/item_foto" android:layout_width="80dp" android:layout_height="80dp" android:src="@drawable/person" />
<LinearLayout android:layout_width="wrap_content" android:layout_height="match_parent" android:gravity="center_vertical" android:orientation="vertical">
<TextView <!-- atributos --> />
<TextView <!-- atributos -->/>
</LinearLayout>
<LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:layout_marginRight="16dp" android:gravity="right" android:orientation="vertical">
<TextView <!-- atributos --> />
<TextView <!-- atributos -->/>
</LinearLayout>
</LinearLayout>

<de.hdodenhof.circleimageview.CircleImageView android:id="@+id/item_foto" android:layout_width="80dp" android:layout_height="80dp" android:padding="5dp" android:src="@drawable/person" />

<de.hdodenhof.circleimageview.CircleImageView android:id="@+id/item_foto" android:layout_width="64dp" android:layout_height="64dp" android:padding="5dp" app:civ_border_width="2dp" app:civ_border_color="#000" android:src="@drawable/person" />