我的代码和老师一样，却没有图标而且报错。图标问题后面会讲吗？

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent">        <LinearLayout        android:layout_width="match_parent"        android:layout_height="0dp"        android:orientation="horizontal"        android:background="#ff0000"        android:layout_weight="2"        >        <RelativeLayout            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="2"            android:background="#ff0000">            <ImageView                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:src="@mipmap/ic_launcher_round"></ImageView>        </RelativeLayout>        <LinearLayout            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="1"            android:orientation="vertical">            <RelativeLayout                android:layout_width="match_parent"                android:layout_height="0dp"                android:layout_weight="1"                android:background="#ffff00">                <ImageView                    android:layout_width="wrap_content"                    android:layout_height="wrap_content"                    android:src="@mipmap/icon_imax2d"></ImageView>            </RelativeLayout>            <RelativeLayout                android:layout_width="match_parent"                android:layout_height="0dp"                android:layout_weight="1"                android:background="#f000">            </RelativeLayout>        </LinearLayout>            </LinearLayout>    <LinearLayout        android:layout_width="match_parent"        android:layout_height="0dp"        android:orientation="horizontal"        android:background="#fff000"        android:layout_weight="1"        >        <RelativeLayout            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="1"            android:background="#00ffff"></RelativeLayout>        <RelativeLayout            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="1"            android:background="#0000ff"></RelativeLayout>        <RelativeLayout            android:layout_width="0dp"            android:layout_height="match_parent"            android:layout_weight="1"            android:background="#ff00ff"></RelativeLayout>    </LinearLayout></LinearLayout>