Render the Camera, or the last photo.

App.js

render() {
  const { photo } = this.state;

  return (
    <View style={{ flex: 1, width: '100%' }}>
     {photo ? (
       <ImageBackground
         style={{ flex: 1 }}
         source={{ uri: photo.uri }} />
     ) : (
       <Camera
         style={{ flex: 1 }}
         onPress={this.takePicture}
         type={Camera.Constants.Type.back}
         ref={cam => this.camera = cam}>
         <TouchableOpacity
           style={{ flex: 1 }}
           onPress={this.takePicture}/>
       </Camera>
     )}
    </View>
  );
}