如何从实时数据库中删除填充有对象的Listview中的重复项

Question

我正在根据从数据库中获取数据，userId然后将数据插入listview并通过对话框显示。

我一直在等待的行为是，我将获得用户创建的所有交换并将其插入列表中，以便他可以选择其中之一。但是，仅当他在数据库中只有一个交换时（如通常显示的那样）时，该代码才能正常工作。但是，如果他有两次交换，则列表内的交换将被乘以2。

如果是3，则数据将重复3次，依此类推。我不知道我的代码在这里的流程是什么，希望有人可以帮助我解决这个问题。如何清除列表中的重复项？

 private void fetchChooseList() {

    DatabaseReference shiftSwapDb = FirebaseDatabase.getInstance().getReference().child("swaps").child("shift_swaps");

    final List<SwapDetails> swapBodyList = new ArrayList<>();
    Collections.reverse(swapBodyList);
    shiftProfileAdapter = new ShiftProfileAdapter(ProfileActivityShift.this, R.layout.shift_profile_list_item, swapBodyList);
    listView = chooseShiftProfileDialog.findViewById(R.id.listShiftProfileChooseDialog);
    listView.setAdapter(shiftProfileAdapter);

    shiftSwapDb.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            if (dataSnapshot.exists()) {
                SwapDetails swapDetails = dataSnapshot.getValue(SwapDetails.class);
                if (swapDetails.getSwapperID().equals(fromID)) {
                    shiftProfileAdapter.add(swapDetails);
                }
            }
        }
        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) { }
        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) { }
        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) { }
        @Override
        public void onCancelled(DatabaseError databaseError) { }
    });


    listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
            progressBar_ShiftProfileChooseDialog.setVisibility(View.VISIBLE);
            listView.setVisibility(View.INVISIBLE);
            SwapDetails swapDetails = swapBodyList.get(adapterView.getCount() - i - 1);
            fromLoginID = swapDetails.getSwapperLoginID();
            fromImageUrl = swapDetails.getSwapperImageUrl();
            fromName = swapDetails.getSwapperName();
            fromPhone = swapDetails.getSwapperPhone();
            fromEmail = swapDetails.getSwapperEmail();
            fromCompanyBranch = swapDetails.getSwapperCompanyBranch();
            fromAccount = swapDetails.getSwapperAccount();
            fromShiftDate = swapDetails.getSwapShiftDate();
            fromShiftDay = swapDetails.getSwapperShiftDay();
            fromShiftTime = swapDetails.getSwapperShiftTime();
            fromPreferredShift = swapDetails.getSwapperPreferredShift();
            String child = fromID + fromShiftDay + fromShiftTime + fromPreferredShift + toID + toShiftDay + toShiftTime + toPreferredShift;
            shiftSwapRequestsDb = FirebaseDatabase.getInstance().getReference().child("Swap Requests").child("Shift Request")
                    .child(child);
            swapRequestShift = new SwapRequestShift(toID,
                    toLoginID,
                    toImageUrl,
                    toName,
                    toPhone,
                    toEmail,
                    toCompanyBranch,
                    toAccount,
                    toShiftDate,
                    toShiftDay,
                    toShiftTime,
                    toPreferredShift,
                    fromID,
                    fromLoginID,
                    fromImageUrl,
                    fromName,
                    fromPhone,
                    fromEmail,
                    fromCompanyBranch,
                    fromAccount,
                    fromShiftDate,
                    fromShiftDay,
                    fromShiftTime,
                    fromPreferredShift,
                    -1,
                    -1);
            shiftSwapRequestsDb.setValue(swapRequestShift)
                    .addOnSuccessListener(new OnSuccessListener<Void>() {
                        @Override
                        public void onSuccess(Void aVoid) {
                            //set the request message
                            requestMessage = userName + "" + " wants to swap with your shift";

                            Map<String, Object> notificationMessage = new HashMap<>();
                            notificationMessage.put("message", requestMessage);
                            notificationMessage.put("from", currentUserId);

                            notificationDB.child(swapperID).push()
                                    .setValue(notificationMessage).addOnCompleteListener(new OnCompleteListener<Void>() {
                                @Override
                                public void onComplete(@NonNull Task<Void> task) {
                                    if (task.isSuccessful()) {
                                        progressBar.setVisibility(View.INVISIBLE);
                                    }
                                }
                            }).addOnFailureListener(new OnFailureListener() {
                                @Override
                                public void onFailure(@NonNull Exception e) {
                                    Toast.makeText(ProfileActivityShift.this, "Something went wrong", Toast.LENGTH_LONG).show();
                                    Log.e(LOG_TAG, "Failed to insert row for " + currentUserId);
                                }
                            });
                            Toast.makeText(ProfileActivityShift.this, "Notification sent", Toast.LENGTH_LONG).show();
                            progressBar_ShiftProfileChooseDialog.setVisibility(View.INVISIBLE);
                            listView.setVisibility(View.VISIBLE);
                            chooseShiftProfileDialog.dismiss();
                            shiftProfileDialog.dismiss();
                            progressBar.setVisibility(View.INVISIBLE);
                            textSentOrAcceptedRequest.setVisibility(View.VISIBLE);
                        }
                    }).addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    Toast.makeText(ProfileActivityShift.this, e.getMessage(), Toast.LENGTH_LONG).show();
                    progressBar_ShiftProfileChooseDialog.setVisibility(View.INVISIBLE);
                    listView.setVisibility(View.VISIBLE);
                    chooseShiftProfileDialog.dismiss();
                    shiftProfileDialog.dismiss();
                    progressBar.setVisibility(View.INVISIBLE);
                    buttonSwapRequest.setVisibility(View.VISIBLE);
                }
            });
        }
    });

}

Answer 1

问题解决了。原因是如果if语句找到了一个用户ID，则将整个数据添加到swapdetails对象中，然后又找到了另一个ID，然后再次添加了所有其他数据，依此类推。

因此，仅在if语句中创建了bloolean，并在找到交换器ID的情况下将其设为true，然后在addChildEventListene范围之外使用html" target="_blank">适配器。

 shiftSwapDb.addChildEventListener(new ChildEventListener() {
    @Override
    public void onChildAdded(DataSnapshot dataSnapshot, String s) {
        if (dataSnapshot.exists()) {
            SwapDetails swapDetails = dataSnapshot.getValue(SwapDetails.class);
            if (swapDetails.getSwapperID().equals(fromID)) {

hasSwaperID = true;
            }
        }
    }

shiftProfileAdapter.add（swapDetails）;