Question

我目前正在使用firebase RecyclerView帮助添加好友，其中如果用户点击ADD按钮，则会在数据库n中添加他需要永久删除被点击的项目..所以，如何通过firebase模型实现它，因为我们没有任何数据列表可以从..

中删除

以下是代码

 @Override
public void onStart(){
    super.onStart();
    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
    EmailPref=prefs.getString("EmailPref", EmailPref);
    if(EmailPref!=null){

        final Firebase ref = new Firebase(constants.FIREBASE_URL+"rootssahaj/authGplus");


        FirebaseRecyclerAdapter<FriendsData,FriendsViewHolder> adapter=new FirebaseRecyclerAdapter<FriendsData, FriendsViewHolder>(
                         FriendsData.class,
                         R.layout.chat_view_list,
                          FriendsViewHolder.class,
                         ref

                    ) {
            @TargetApi(Build.VERSION_CODES.KITKAT)
            @Override
            protected void populateViewHolder(FriendsViewHolder friendsViewHolder, FriendsData s, int position) {
                String key = this.getRef(position).getKey();
                Log.e("SahajLOG", "String Keyyy " + key + " n EmailPref" + EmailPref);

                if (!Objects.equals(key, EmailPref)) {
                    friendsViewHolder.mName.setText(s.getUserNAME());
                    Picasso.with(context).load(s.getPicurl()).transform(new CircleTransform()).into(friendsViewHolder.mImageProfile);


                    String keylocal = key;
                    Log.e("pavan", "Populate AddF key" + keylocal+" " + position);
                    SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
                    prefs.getString("keylocal" + position, keylocal + position);
                    if (keylocal != null) {
                        prefs.edit().putString("keylocal" + position, keylocal + position).commit();
                    }
                } else {
                    friendsViewHolder.mCardView.setVisibility(View.GONE);
                    //friendsViewHolder.setVisibility(View.GONE);
                }

            }
        };

        recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
        recyclerView.setItemAnimator(new SlideInLeftAnimator());
        recyclerView.getItemAnimator().setAddDuration(1000);
        recyclerView.getItemAnimator().setRemoveDuration(1000);
        recyclerView.getItemAnimator().setMoveDuration(1000);
        recyclerView.getItemAnimator().setChangeDuration(1000);


        SlideInLeftAnimator animator = new SlideInLeftAnimator();
        animator.setInterpolator(new OvershootInterpolator());
        recyclerView.setItemAnimator(animator);
        AlphaInAnimationAdapter alphaAdapter = new AlphaInAnimationAdapter(adapter);
        alphaAdapter.setDuration(500);
        alphaAdapter.setInterpolator(new OvershootInterpolator(.5f));
        alphaAdapter.setFirstOnly(false);
        recyclerView.setAdapter(new ScaleInAnimationAdapter(alphaAdapter));


    }
}

public class FriendsViewHolder extends RecyclerView.ViewHolder{
    ImageView mImageProfile;
    android.widget.TextView mName;
    private int mVisibility;
    Boolean CallAdd=false;
    Button mAdd;
    String keylocal;
    CardView mCardView;

    public FriendsViewHolder(View itemView) {
        super(itemView);
        mCardView=(CardView)itemView.findViewById(R.id.cardView);
        mImageProfile=(ImageView)itemView.findViewById(R.id.profilePICC);
        mName=(android.widget.TextView)itemView.findViewById(R.id.NameUSER);
        context = itemView.getContext();
        mAdd=(Button)itemView.findViewById(R.id.addButton);
        SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(context);
        if(prefs.getBoolean("CallAdd", CallAdd)){
            AddaddButton();

        }

        mAdd.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(mContext);
               EmailPref = prefs.getString("EmailPref", EmailPref);
               keylocal=prefs.getString("keylocal"+getAdapterPosition(),keylocal+getAdapterPosition());

               final Firebase mFirebaseRef = new Firebase(constants.FIREBASE_URL + "rootssahaj/authGplus/"+ EmailPref);
                mFirebaseRef.child("friends").child(keylocal).setValue("true");
                Log.e("pavan", "Chat Adapter " + EmailPref + keylocal + " final key: " + keylocal);
                //remove(getAdapterPosition());

            }
        });
    }
    public void AddaddButton(){
        if (mAdd.getVisibility() == View.INVISIBLE) {
            mAdd.setVisibility(View.VISIBLE);
        }
    }

}

Answer 1

FirebaseUI FirebaseRecyclerAdapter直接代表基础Query或Firebase位置的数据。要从适配器（和视图）中删除项目，您必须将其从Firebase位置删除（或确保它不再与查询匹配）。

因此，当用户触发删除时（例如，通过点击特定位置的项目）：

adapter.getRef(position).remove()

另见issue in the FirebaseUI Github repo。

Answer 2

如果您查看此代码，则会从Firebase中删除Note 单击注释。如果您了解Firebase查询，这似乎很简单。一旦正确设置了RecyclerView适配器，这也将更新RecyclerView。您不需要数据列表，只需要删除内容的值，例如ID或密钥。

       @Override
        public void onLongClick(View v, int i) {
            mquery.orderByChild("text")
                    .equalTo((String) notes.get(i).getName())
                    .addListenerForSingleValueEvent(new ValueEventListener() {
                        public void onDataChange(DataSnapshot dataSnapshot) {
                            if (dataSnapshot.hasChildren()) {
                                DataSnapshot firstChild = dataSnapshot.getChildren().iterator().next();
                                firstChild.getRef().removeValue();
                            }
                        }

                        public void onCancelled(FirebaseError firebaseError) {
                        }
                    });

来自https://github.com/mmazzarolo/firebase-recyclerview的FirebaseRecyclerAdapter.class有效。在大多数情况下，我只是复制和粘贴。这是一个抽象类，可用于为Firebase数据库创建RecyclerView适配器。所有代码都在您的GitHub存储库中。以下是来自FirebaseRecyclerAdapter.class的代码段，用于从Firebase中删除值并更新recyclerView：

    @Override
    public void onChildRemoved(DataSnapshot dataSnapshot) {
        String key = dataSnapshot.getKey();

        if (mKeys.contains(key)) {
            int index = mKeys.indexOf(key);
            T item = mItems.get(index);

            mKeys.remove(index);
            mItems.remove(index);

            notifyItemRemoved(index);
            itemRemoved(item, key, index);
        }
    }

更新：您可以在RecyclerView适配器的Viewholder中隐藏视图。在stackoverflow Hiding views in RecyclerView

中查看这些答案

Answer 3

现在您可以轻松删除特定的孩子

（1）-第一步创建方法，代码如下：

private void deleteRef(String id) { 

    databaseRef.child(id).removeValue();

}

（2）-第二步，在您想要的地方，例如下面的AlertDialog副本中的警报对话框或Firebase回收器适配器中调用此方法：

public void alertDelete(final String id) { 

    AlertDialog.Builder dialogBuilder = new AlertDialog.Builder(this);
    LayoutInflater inflater = getLayoutInflater();
    final View dialogView = inflater.inflate(R.layout.warning_delete, null);
    dialogBuilder.setView(dialogView);
    final AlertDialog alertDialog = dialogBuilder.create();
    alertDialog.show();

    final Button deete = dialogView.findViewById(R.id.delete);

    delete.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            deleteRef(id);
            alertDialog.dismiss();
            Toast.makeText(Teachers_Admin_Activity.this,"Delete Successfully",Toast.LENGTH_LONG).show();                 
        }
    });
}

（3）或像这样从recyclerview子节点删除，但请记住必须从ViewHolder进行调用：

@Override
protected void onBindViewHolder(@NonNull final BlogViewHolder holder, final int position, @NonNull final TeachersName model) {

    // this is method in viewholer where you next step to delete specific child node // 
    DatabaseReference itemRef = getRef(position);
    final String myKeyItem = itemRef.getKey();
}

（4）-onclicklistener的最后一步：

holder.deleteImage.setOnLongClickListener(new View.OnLongClickListener() {
    @Override
    public boolean onLongClick(View v) {
        alertDelete(myKeyItem);
        return true;
    }
});

如何从firebase RecyclerView中删除项目

3 个答案: