java - 使用 SwipRefresh 库刷新 recyclerview 时 onDatachange 给出错误

Question

我正在使用 SwipRefresh 布局刷新我的 recyclerview 但当我添加 recyclerview 方法时在 SwipRefresh 的 onRefresh 内部，我在空对象引用上收到 Datachange 错误，但在不使用 swipreferesh 的情况下，它工作正常，这是我的代码。我尝试了所有可能的方法，但无法解决我的问题，请提供任何建议，谢谢。

  private void Geofireinit() {
    started = true;
    GeoQuery geoQuery = fire.queryAtLocation(new GeoLocation(20.887715, 77.757623), 50);
    geoQuery.addGeoQueryEventListener(new GeoQueryEventListener() {
        @Override
        public void onKeyEntered(String key, GeoLocation location) {


            Log.e("id", key);
            Location to = new Location("to");
            to.setLatitude(location.latitude);
            to.setLongitude(location.longitude);
            if (!fetchedUserIds) {
                userIdsToLocations.put(key, to);

            } else {
                userIdsToLocations.put(key, to);
                addUserListener(key);
            }


        }

        @Override
        public void onKeyExited(String key) {
            Log.d("TAG", "onKeyExited: ");
            if (userIdsWithListeners.contains(key)) {
                int position = getUserPosition(key);
                if (position!=-1) {
                    arrayList.remove(position);
                    adapter.notifyItemRemoved(position);
                }

            }
        }

        @Override
        public void onKeyMoved(String key, GeoLocation location) {

        }

        @Override
        public void onGeoQueryReady() {

            initialListSize = userIdsToLocations.size();
            if (initialListSize == 0) {
                fetchedUserIds = true;
            }
            iterationCount = 0;
            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
                userIdsToLocations.keySet().forEach(this::addUserListener);
            }
        }

        private void addUserListener(String key) {
            myref = FirebaseDatabase.getInstance().getReference().child("buses").child(key);
            myref.addListenerForSingleValueEvent(userValueListener);
            userIdsWithListeners.add(key); // myreference
       }

        @Override
        public void onGeoQueryError(DatabaseError error) {

        }
    });


    geoQueries.add(geoQuery);
}



private void setuplist() {
    recyclerView.setLayoutManager(new LinearLayoutManager(this));
    adapter = new Adapter(this, arrayList);
    recyclerView.setAdapter(adapter);
}

@Override
public void onRefresh() {

    getrecyclerview(); // getting error when adding this method inside onRefresh
}
private void getrecyclerview() {
    swipeRefreshLayout.setRefreshing(true);
    userValueListener = new ValueEventListener() {

        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            swipeRefreshLayout.setRefreshing(false);

            Mylist mylist = dataSnapshot.getValue(Mylist.class);
            mylist.setText(dataSnapshot.child("text").getValue().toString());

            if (arrayList.contains(mylist)) {

                update(mylist);
            } else {

                newdata(mylist);
            }


        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {

        }
    };

}

Logcat错误

 java.lang.NullPointerException: Attempt to invoke interface method 'void com.google.firebase.database.ValueEventListener.onDataChange(com.google.firebase.database.DataSnapshot)' on a null object reference

Answer 1

我建议不要使用该库，而应使用 native swiperefreshlayout。像这样的事情:

XML:

<androidx.swiperefreshlayout.widget.SwipeRefreshLayout
        android:id="@+id/swipeRefresh"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintBottom_toBottomOf="parent">

        <androidx.recyclerview.widget.RecyclerView
            android:id="@+id/rvMyRecyclerView"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
          />

    </androidx.swiperefreshlayout.widget.SwipeRefreshLayout>

然后在 Activity/fragment 中执行以下操作:

swipeRefresh.setOnRefreshListener {

        getrecyclerview()
        swipeRefresh.isRefreshing = false
    }

并且您的 getrecyclerview() 函数不应包含此行 swipeRefreshLayout.setRefreshing(true);

让我知道它是否有效!