Show image from Firebase with React Native

I‘m trying to show my images from Firebase with React Native - but i can’t. When I log sampleImage, I see JSON-like data and I can see a link in this data's i section. But when I log imageUrl, it returns undefined. I want to see my picture in imageView. By the way I saved the image's names with user's ids.

render() {
    const uid = '12345';     
    const imageRef = firebase.storage().ref(uid).child(uid);
    const sampleImage = imageRef.getDownloadURL().then();
    const imageUrl = sampleImage.i;
    console.log(sampleImage);    
    console.log(imageUrl);
    return (
        <View>
            <Image style={{ width: 55, height: 55 }} source={{ uri: null }} />
         </View>
    );
}
}