Cómo declarar la imagen para poder subirla a firebase junto a los demas datos?

(EDITADO)
Leyendo la documentacion de firebase mi MainActivity queda asi…pero al correr en el emulador se me cierra la app…

public class MainActivity2 extends AppCompatActivity implements AdapterView.OnItemClickListener {

private EditText tv_nombre, tv_precio, tv_detalle;

private ImageView imagen;
private ListView mListView;
private List<Modelo> mLista;

private StorageReference storageRef;
private DatabaseReference databaseReference;
private ProgressBar mProgressBar;
private Uri mImageUri;

ListAdapter mAdapter;
FirebaseFirestore mFirestore;
FirebaseStorage storage;


@SuppressLint("WrongThread")
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    mFirestore = FirebaseFirestore.getInstance();



    mListView = findViewById(R.id.listView);
    mListView.setOnItemClickListener(this);

    imagen.setDrawingCacheEnabled(true);
    imagen.buildDrawingCache();


    mLista = new ArrayList<>();
    mLista.add(new Modelo(" Zapatos de futbol 1", "$ 56.99", "Nike Tiempo Legend VIII", R.mipmap.pupos1));
    mLista.add(new Modelo(" Zapatos de futbol 2", "$ 71.49", "Nike Phantom Vision 2", R.mipmap.pupos2));
    mLista.add(new Modelo(" Zapatos de futbol 3", "$ 37.49", "New Balance Furon v5", R.mipmap.pupos3));
    mLista.add(new Modelo(" Zapatos de futbol 4", "$ 18.49", "Umbro Classico V AG", R.mipmap.pupos4));

    mAdapter = new ListAdapter(this, R.layout.item_row, mLista);
    mListView.setAdapter(mAdapter);


}


@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {

    Bitmap bitmap = ((BitmapDrawable) imagen.getDrawable()).getBitmap();
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    bitmap.compress(Bitmap.CompressFormat.JPEG, 100, baos);
    byte[] data = baos.toByteArray();
    StorageReference storageRef = storage.getReference();

    StorageReference puposRef = storageRef.child("pupos1.jpg");

    StorageReference puposImagesRef = storageRef.child("images/pupos1");
    puposRef.getName().equals(puposImagesRef.getName());    // true
    puposRef.getPath().equals(puposImagesRef.getPath());

    UploadTask uploadTask = puposImagesRef.putBytes(data);
    uploadTask.addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {

        }
    }).addOnSuccessListener(new OnSuccessListener<UploadTask.TaskSnapshot>() {
        @Override
        public void onSuccess(UploadTask.TaskSnapshot taskSnapshot) {

        }
    });

    String nombre = tv_nombre.getText().toString();
    String precio = tv_precio.getText()introducir el código aquí.toString();
    String detalle = tv_detalle.getText().toString();

    Map<String, Object> map = new HashMap<>();
    map.put("Nombre", nombre);
    map.put("Precio", precio);
    map.put("Detalle", detalle);


    mFirestore.collection("Modelo").add(map).addOnSuccessListener(new OnSuccessListener<DocumentReference>() {
        @Override
        public void onSuccess(DocumentReference documentReference) {
            Toast.makeText(MainActivity2.this, "Producto Seleccionado", Toast.LENGTH_SHORT).show();
        }
    }).addOnFailureListener(new OnFailureListener() {
        @Override
        public void onFailure(@NonNull Exception e) {
            Toast.makeText(MainActivity2.this, "Error", Toast.LENGTH_SHORT).show();
        }
    });


}

}
/////ADJUNTO EL ERROR QUE ME APARECE EN EL RUN, SE ME ACABARON LAS IDEAS Y SIGO SIN PODER SUBIR LA IMAGEN JUNTO A MIS DEMAS DATOS A FIREBASE//////////

07/25 17:15:38: Launching 'app' on Pixel 3a API 30.
$ adb shell am start -n "com.example.cgpractica/com.example.cgpractica.MainActivity2" -a android.intent.action.MAIN -c android.intent.category.LAUNCHER
Connected to process 23649 on device 'emulator-5554'.
Capturing and displaying logcat messages from application. This behavior can be disabled in the "Logcat output" section of the "Debugger" settings page.
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
D/NetworkSecurityConfig: No Network Security Config specified, using platform default
I/MultiDex: VM with version 2.1.0 has multidex support
    Installing application
I/MultiDex: VM has multidex support, MultiDex support library is disabled.
I/FirebaseInitProvider: FirebaseApp initialization successful
I/DynamiteModule: Considering local module com.google.android.gms.measurement.dynamite:15 and remote module com.google.android.gms.measurement.dynamite:0
I/DynamiteModule: Selected local version of com.google.android.gms.measurement.dynamite
D/libEGL: loaded /vendor/lib/egl/libEGL_emulation.so
D/libEGL: loaded /vendor/lib/egl/libGLESv1_CM_emulation.so
D/libEGL: loaded /vendor/lib/egl/libGLESv2_emulation.so
W/mple.cgpractic: Unsupported class loader
W/mple.cgpractic: Unsupported class loader
V/FA: onActivityCreated
W/mple.cgpractic: Accessing hidden method Landroid/view/View;->computeFitSystemWindows(Landroid/graphics/Rect;Landroid/graphics/Rect;)Z (greylist, reflection, allowed)
W/mple.cgpractic: Accessing hidden method Landroid/view/ViewGroup;->makeOptionalFitsSystemWindows()V (greylist, reflection, allowed)
D/AndroidRuntime: Shutting down VM
E/AndroidRuntime: FATAL EXCEPTION: main
    Process: com.example.cgpractica, PID: 23649
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.cgpractica/com.example.cgpractica.MainActivity2}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setDrawingCacheEnabled(boolean)' on a null object reference
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3449)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:223)
        at android.app.ActivityThread.main(ActivityThread.java:7656)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageView.setDrawingCacheEnabled(boolean)' on a null object reference
        at com.example.cgpractica.MainActivity2.onCreate(MainActivity2.java:74)
        at android.app.Activity.performCreate(Activity.java:7995)
        at android.app.Activity.performCreate(Activity.java:7979)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3422)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3601) 
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85) 
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135) 
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95) 
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066) 
        at android.os.Handler.dispatchMessage(Handler.java:106) 
        at android.os.Looper.loop(Looper.java:223) 
        at android.app.ActivityThread.main(ActivityThread.java:7656) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947) 
V/FA: App measurement collection enabled
V/FA: App measurement enabled for app package, google app id: com.example.cgpractica, 1:482635389447:android:13cf0723f55607780728a2
I/FA: App measurement initialized, version: 31000
    To enable debug logging run: adb shell setprop log.tag.FA VERBOSE
    To enable faster debug mode event logging run:
      adb shell setprop debug.firebase.analytics.app com.example.cgpractica
D/FA: Debug-level message logging enabled
W/mple.cgpractic: Verification of java.lang.Object com.google.android.gms.measurement.internal.zzm.createFromParcel(android.os.Parcel) took 215.207ms (1356.83 bytecodes/s) (6016B approximate peak alloc)
V/FA: Connecting to remote service
V/FA: Connection attempt already in progress

/////ADJUNTO EL ERROR QUE ME APARECE EN EL RUN, SE ME ACABARON LAS IDEAS Y SIGO SIN PODER SUBIR LA IMAGEN JUNTO A MIS DEMAS DATOS A FIREBASE//////////

////Logre subir la imagen a firebase, tenia que convertir la imagen a bytes, por si alguien lo necesita dejo el codigo.

private String encodeImage(Bitmap bm) {
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        bm.compress(Bitmap.CompressFormat.JPEG,100,baos);
        byte[] b = baos.toByteArray();
        String img = Base64.encodeToString(b, Base64.DEFAULT);
        return img;`introducir el código aquí`
    }

final StorageReference ref = storageRef.child("images/mountains.jpg"); // -> Donde guardamos la imagen en Firebase Storage
uploadTask = ref.putFile(file);  // -> Acá file deberia ser el bitmap de la imagen

Task<Uri> urlTask = uploadTask.continueWithTask(new Continuation<UploadTask.TaskSnapshot, Task<Uri>>() {
    @Override
    public Task<Uri> then(@NonNull Task<UploadTask.TaskSnapshot> task) throws Exception {
        if (!task.isSuccessful()) {
            throw task.getException();
        }

        return ref.getDownloadUrl();
    }
}).addOnCompleteListener(new OnCompleteListener<Uri>() {
    @Override
    public void onComplete(@NonNull Task<Uri> task) {
        if (task.isSuccessful()) {
            Uri downloadUri = task.getResult();  // -> una vez subida la imagen a Firebase obtenemos la url de la imagen de ser necesario
        } else {
            // Maneja fallos si no se cargó correctamente
            // ...
        }
    }
});