继续滑动菜单的完善，NavigationView，图片圆形化-CircleImageView

    compile ‘com.android.support:design:25.0.0‘库的引用
    compile ‘de.hdodenhof:circleimageview:2.1.0‘开源项目，实现图片圆形化

    <android.support.design.widget.NavigationView
        android:id="@+id/nav_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:elevation="10dp"
        app:headerLayout="@layout/nav_header"另建一个header.xml文件，并且引用进来，里面存放group标签和item标签
        app:menu="@menu/nav_menu" />

 final NavigationView navView = (NavigationView) findViewById(R.id.nav_view);
        navView.setCheckedItem(R.id.nav_call);//默认选中的条目
        navView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
            @Override
            public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                mDrawerLayout.closeDrawers();
                return true;
            }
        });

 <de.hdodenhof.circleimageview.CircleImageView
        android:id="@+id/icon_image"
        android:layout_width="70dp"
        android:layout_height="70dp"
        android:src="@drawable/nav_icon"
        android:layout_centerInParent="true"/>居中显示