我正在嘗試使用來自 firebase 的 Glide 庫加載圖像。圖片 url 正確（使用 Logcat 檢查）。我在活動中使用滑行而不是片段。我收到這個錯誤 java.lang.NullPointerException: You cannot start a load on a not yet attached View or a Fragment where getActivity() returns null (which usually occurs when getActivity() is called before the Fragment is attached or after the Fragment is destroyed).這是我的代碼：public class ProfileActivity extends AppCompatActivity {FirebaseAuth auth;DatabaseReference databaseReference;TextView nameTextView , bioTextView;String name2 , bio2 , uidString;Uri imageUri , FilePathUri;Button logOut , editProfile;private SlidrInterface slidr;CircleImageView profilepic;StorageReference storageReference;String Storage_Path = "ProfilePictures/" , downloadUrl;Context context;@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_profile);    auth = FirebaseAuth.getInstance();    databaseReference = FirebaseDatabase.getInstance().getReference();    final FirebaseUser user = auth.getCurrentUser();    nameTextView = (TextView) findViewById(R.id.name);    bioTextView = (TextView) findViewById(R.id.bio);    logOut = (Button) findViewById(R.id.logout2);    editProfile = (Button) findViewById(R.id.editprofile);    slidr = Slidr.attach(this);    profilepic = (CircleImageView) findViewById(R.id.profilepic);    storageReference = FirebaseStorage.getInstance().getReference();    Intent intent = getIntent();    Bundle uid = intent.getExtras();    uidString = uid.getString("UID");    Log.d("UID OF USER" , "UID OF USER = "+uidString);    final Context finalContext = context;    databaseReference.child("users").child(uidString).addValueEventListener(new ValueEventListener() {        }如果我不使用片段，為什么會出現此錯誤。另外我將如何解決這個錯誤。請幫我