1.布局文件

<android.support.v7.widget.CardView
    android:id="@+id/cv_img_activity"
    android:layout_width="200dp"
    android:layout_height="200dp"
    app:cardCornerRadius="100dp"
    app:cardElevation="10dp"
    app:cardPreventCornerOverlap="true">

    <ImageView
        android:id="@+id/iv_cv_img_activity"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="centerCrop"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textColor="@color/colorAccent"
        android:textSize="30sp"
        android:layout_gravity="bottom|center_horizontal"
        android:text="圆"/>
</android.support.v7.widget.CardView>

CardView继承的FramLayout。宽和高都为200dp，设置圆角半径为100dp

2.Aciticy中代码

使用的Glide进行图片加载

public class ImgActivity extends AppCompatActivity {
    private static final String url = "https://timgsa.baidu.com/timg?image&quality=80&size=b10000_10000&sec=1473082549776&di=cb9749bd976beb119da065ee56ebbc60&imgtype=jpg&src=http%3A%2F%2Fstatic.oneplus.cn%2Fdata%2Fattachment%2Fforum%2F201410%2F18%2F111437v9ll9869qqmq76n7.jpg";
    private CardView cardView;
    private ImageView iv_cv;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_img);
        init();
    }

    private void init() {
        cardView = (CardView) findViewById(R.id.cv_img_activity);
        iv_cv = (ImageView) findViewById(R.id.iv_cv_img_activity);
    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        if (hasFocus){
              Glide.with(ImgActivity.this).load(url).override(cardView.getWidth(),cardView.getHeight()).into(iv_cv);
        }
    }

}

onWindowFocusChanged(boolean hasFocus)这个方法可以用来判断Activity是否已经获得焦点，这个时候可以拿到控件的宽和高，是拿到控件宽高的一种办法。