Android-imageView.getDrawable ()이 null을 반환합니다.

나는이 겉보기에 쉬운 문제에 갇혀있다. 내가 도대체 ​​뭘 잘못하고있는 겁니까 ?

ImageView mImageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        mImageView = (ImageView)findViewById(R.id.control);
        ClipDrawable drawable = (ClipDrawable)mImageView.getDrawable();
        drawable.setLevel(10);

    }

앱이 drawable.setLevel (10)에서 NullPointerException (drawable이 null 임)과 함께 충돌합니다.

내 XML은 다음과 같습니다.

circle.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval"
    android:innerRadius="50dp"
    >

    <solid
        android:color="#FFAAFF"/>

</shape>

clip.xml

<?xml version="1.0" encoding="utf-8"?>
<clip xmlns:android="http://schemas.android.com/apk/res/android"
    android:clipOrientation="horizontal"
    android:drawable="@drawable/circle"
    android:gravity="clip_horizontal"

/>

activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <ImageView
        android:id="@+id/image"
        android:layout_height="100dp"
        android:layout_width="100dp"
        android:background="@drawable/clip"
        android:layout_centerHorizontal="true"
        />

</RelativeLayout>

제발 도와주세요!