java - 使用 firebase 在 recyclerView 中拖放

Question

我正在尝试在使用 FirebaseRecyclerAdapter 的 recyclerView 中实现拖放功能。我在 firebase child 中有一个属性，用于存储其订单位置并重新排序我发现类似的数据:

  @Override
    public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
        final int firstPosition = viewHolder.getAdapterPosition();;
        final int secondPosition = target.getAdapterPosition();
        DatabaseReference firstItemRef = fireBaseRvAdapter.getRef(viewHolder.getAdapterPosition());
        DatabaseReference secondItemRef = fireBaseRvAdapter.getRef(target.getAdapterPosition());

        HashMap<String, Object> updateFirstItemOrderNumber = new HashMap<>();
        updateFirstItemOrderNumber.put(FBdatabase.FIELD_ORDER, secondPosition);
        firstItemRef.updateChildren(updateFirstItemOrderNumber);

        HashMap<String, Object> updateSecondItemOrderNumber = new HashMap<>();
        updateSecondItemOrderNumber.put(FBdatabase.FIELD_ORDER, firstPosition);
        secondItemRef.updateChildren(updateSecondItemOrderNumber);

        return false;
    }

但拖动在第一次交换后自行停止，然后列表奇怪地动画化。它改变了顺序，但看起来不太好。

Answer 1

我会添加更多解释，但稍后……再次)

public class CustomFirebaseAdapter extends RecyclerView.Adapter<CustomFirebaseAdapter.RecordViewHolderIns>
        implements ValueEventListener, ChildEventListener {

private static final String TAG = "CustomFerebaseAdapter";
private OnItemClickListener onItemClickListener; //custom interface
private int maxOrderValue;
private ArrayList<Record> records = new ArrayList<>();
private ArrayList<DatabaseReference> references = new ArrayList<>();
public boolean isDragging = false;
private Query mainQuery;
private int textSize=9;


public CustomFirebaseAdapter(Class<Record> modelClass, @LayoutRes int modelLayout,
                             Class<MyFireBaseRvAdapter.RecordViewHolderIns> viewHolderClass, Query query) {
    mainQuery = query;
// getting max order value to insert new record with  maxOrderValue + 1

    mainQuery.limitToLast(1)
            .addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {

                    for (DataSnapshot ds : dataSnapshot.getChildren()) {
                        Record r = ds.getValue(Record.class);
                        maxOrderValue = r.getPositionInList();
                        Log.d(TAG, "onDataChange: max value = " + maxOrderValue);
                        Log.d(TAG, "onDataChange: max value = " + r.getText());

                    }

                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });
    //listner for first update
    mainQuery.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            updateArrays(dataSnapshot);
            notifyDataSetChanged();
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

    mainQuery.addValueEventListener(this);
    mainQuery.addChildEventListener(this);
}

@Override
public CustomFirebaseAdapter.RecordViewHolderIns onCreateViewHolder(ViewGroup parent, int viewType) {
    View inflatedView = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.list_item, parent, false);
    return new CustomFirebaseAdapter.RecordViewHolderIns(inflatedView);
}

@Override
public void onBindViewHolder(RecordViewHolderIns holder, int position) {
    populateViewHolder(holder, records.get(position), position);
}

public ArrayList<Record> getRecords() {
    return records;
}

public ArrayList<DatabaseReference> getReferences() {
    return references;
}

protected void populateViewHolder(CustomFirebaseAdapter.viewHolder, Record model, int position) {
//.................................
}

public void setTextSize(int textSize){
    this.textSize =textSize;
}
public void setOnItemClickListener(OnItemClickListener onItemClickListener) {
    this.onItemClickListener = onItemClickListener;
}

public int getMaxOrderValue() {
    return maxOrderValue;
}

public Record getItem(int position) {
    return records.get(position);
}

public DatabaseReference getRef(int position) {
    return references.get(position);
}

ArrayList<Record> snapshotList;

public ArrayList<Record> getDataSnapshot() {
    return snapshotList;
}


public void onDataChanged() {

}

public void onItemMoved(int itemPos, int targetPos) {

    if (itemPos < targetPos) {
        for (int i = itemPos; i < targetPos; i++) {
            Collections.swap(records, i, i + 1);
            Collections.swap(references, i, i + 1);
        }
    } else {
        for (int i = itemPos; i > targetPos; i--) {
            Collections.swap(records, i, i - 1);
            Collections.swap(references, i, i - 1);
        }
    }
    notifyItemMoved(itemPos, targetPos);

}


@Override
public int getItemViewType(int position) {
    return 0;
}

@Override
public int getItemCount() {
    return records.size();
}

public void stopListening() {

}

private void updateArrays(DataSnapshot dataSnapshot){
    records.clear();
    references.clear();
    for (DataSnapshot snapshot : dataSnapshot.getChildren()) {
        references.add(snapshot.getRef());
        records.add(snapshot.getValue(Record.class));
    }

}

@Override
public void onDataChange(DataSnapshot dataSnapshot) {
    if (!isDragging) {
        updateArrays(dataSnapshot);

    }
}

@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
    Log.d(TAG, "onChildAdded: "+dataSnapshot.toString());
}

@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
    int i=-1;
    for (DatabaseReference r : references) {
        if(dataSnapshot.getKey().equals(r.getKey())){
            i = references.indexOf(r);
            break;
        }
    }
    if(i!=-1){
        records.set(i, dataSnapshot.getValue(Record.class  ));
        references.set(i, dataSnapshot.getRef());
        if(!isDragging) notifyItemChanged(i);
    }
}

@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
    int i=-1;
    for (DatabaseReference r : references) {
        if(dataSnapshot.getKey().equals(r.getKey())){
            i = references.indexOf(r);
            break;
        }
    }
    if(i!=-1){
        records.remove(i);
        references.remove(i);
        notifyItemRemoved(i);
    }
    Log.d(TAG, "onChildRemoved: child: "+i+" " +dataSnapshot.toString());
}

@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {

}

@Override
public void onCancelled(DatabaseError databaseError) {

}

public void onStartDragging() {
    isDragging = true;
}

public void onStopDragging() {
    isDragging = false;
}

public class RecordViewHolderIns extends RecyclerView.ViewHolder {
    public TextView text;
    public TextView date;


    public RecordViewHolderIns(final View itemView) {
        super(itemView);
        text = itemView.findViewById(R.id.activ_item_text);
        date = itemView.findViewById(R.id.record_date);


        itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (onItemClickListener != null) {
                    onItemClickListener.onItemClick(v, getAdapterPosition());
                }
            }
        });

    }


    }
}

触控助手...

  ItemTouchHelper.SimpleCallback simpleCallback = new ItemTouchHelper.SimpleCallback(
            ItemTouchHelper.UP | ItemTouchHelper.DOWN, ItemTouchHelper.LEFT | ItemTouchHelper.RIGHT) {

        @Override
        public boolean isItemViewSwipeEnabled() {
            return false;
        }

        @Override
        public void onSelectedChanged(RecyclerView.ViewHolder viewHolder, int actionState) {
            super.onSelectedChanged(viewHolder, actionState);
            if (actionState == ItemTouchHelper.ACTION_STATE_DRAG) {
                fireBaseRvAdapter.onStartDragging();
            } else if (actionState == ItemTouchHelper.ACTION_STATE_IDLE) {

            }
        }

        @Override
        public boolean onMove(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder, RecyclerView.ViewHolder target) {
            final int firstPosition = viewHolder.getAdapterPosition();
            final int secondPosition = target.getAdapterPosition();
            DatabaseReference firstItemRef = fireBaseRvAdapter.getRef(viewHolder.getAdapterPosition());
            DatabaseReference secondItemRef = fireBaseRvAdapter.getRef(target.getAdapterPosition());

            firstItemRef.child(FBdatabase.FIELD_ORDER).setValue(secondPosition);

            secondItemRef.child(FBdatabase.FIELD_ORDER).setValue(firstPosition);

            fireBaseRvAdapter.onItemMoved(firstPosition, secondPosition);
            return true;
        }

        @Override
        public void onSwiped(RecyclerView.ViewHolder viewHolder, int direction) {

        }

        @Override
        public void clearView(RecyclerView recyclerView, RecyclerView.ViewHolder viewHolder) {
            super.clearView(recyclerView, viewHolder);
            fireBaseRvAdapter.onStopDragging();

        }
    };

在您的 Activity 中初始化 recyclerView:

 recycleListView = (RecyclerView) findViewById(R.id.list);
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this);
        recycleListView.setLayoutManager(layoutManager);
        DefaultItemAnimator an = new DefaultItemAnimator();
        recycleListView.setItemAnimator(an);

        //Firebase
        fb = new FBdatabase(); //Some firebase initialization here

        fireBaseRvAdapter = new CustomFirebaseAdapter(
                Record.class,
                R.layout.list_item,
                MyFireBaseRvAdapter.RecordViewHolderIns.class,
                fb.getRef().orderByChild(FBdatabase.FIELD_ORDER)
        );
        fireBaseRvAdapter.setOnItemClickListener(this);
        recycleListView.setAdapter(fireBaseRvAdapter);

        //Firebase

        ItemTouchHelper itemTouchHelper = new ItemTouchHelper(simpleCallback);
        itemTouchHelper.attachToRecyclerView(recycleListView);