Question

如何在适配器的顶部显示新数据？这是代码：-

对不起，刚才我发现我错误地复制了代码。对不起这是我的错。现在的问题是我想在适配器顶部显示最新的广告。...

mDatabase.child("Advertisement").child(mAuth.getUid()).addValueEventListener(new ValueEventListener()
    {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot)
        {
            //iterating through all the values in database
            mChildrenList = new ArrayList<>();
            for (DataSnapshot postSnapshot : dataSnapshot.getChildren())
            {
                Advertisement advertisement = postSnapshot.getValue(Advertisement.class);
                mChildrenList.add(advertisement);
            }
            //Creating adapter
            mAdapter = new AdvertisementAdapter(getApplicationContext(), mChildrenList, "AddAds");

            //Adding adapter to recyclerview
            mRecyclerView.setAdapter(mAdapter);

            //mAdapter.notifyItemChanged(0);
        }

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

        }
    });

Answer 1

此行：

tuitionPackageList.add(0, new TuitionPackage(tuitionPackageList));

您收到一个错误，因为您正在实例化一个以TuitionPackage作为参数的tuitionPackageList对象，并且我认为这是不正确的。
在代码的前面，您只是使用以下示例进行了相同的实例化：

TuitionPackage tuitionPackage = new TuitionPackage();

，然后将该项目添加到列表的末尾。
您是否要在位置0添加此项目？
编辑更改为此：

else {
    TuitionPackage tuitionPackage = new TuitionPackage();
    tuitionPackage.setPrice(mPriceView.getText().toString());
    tuitionPackageList.add(0, tuitionPackage);
    mPackageAdapter.notifyItemInserted(0);
}

Answer 2

用此替换最后一个else块

    TuitionPackage tuitionPackage = new TuitionPackage();
    tuitionPackage.setPrice(mPriceView.getText().toString());
    tuitionPackageList.add(tuitionPackage);
    mPackageAdapter.notifyDataSetChanged();

Answer 3

在上面的代码的帮助下，这是我的答案，将第一个广告排在最高位置：-

//Iterating through all the values in database
            mChildrenList = new ArrayList<>();
            for (DataSnapshot postSnapshot : dataSnapshot.getChildren())
            {
                Advertisement advertisement = postSnapshot.getValue(Advertisement.class);
                mChildrenList.add(0, advertisement);
            }

            //Creating adapter
            mAdapter = new AdvertisementAdapter(getApplicationContext(), mChildrenList, "AddAds");

            //Adding adapter to recyclerview
            mRecyclerView.setAdapter(mAdapter);
            mAdapter.notifyItemInserted(0);

如何在适配器的顶部显示新项目？

3 个答案: