Question

我正在尝试将数据从回收站适配器传递给活动。目前，我正在尝试在下面使用更多意图的信息

适配器

public class BlogRecyclerAdapter extends RecyclerView.Adapter<BlogRecyclerAdapter.ViewHolder> {

public List<BlogPost> blog_list;

private FirebaseFirestore firebaseFirestore;
private FirebaseDatabase firebaseDatabase;

private DatabaseReference mUserDatabase;
private FirebaseUser mCurrentUser;

private Context mContext;


public BlogRecyclerAdapter(Context context, List<BlogPost> blog_list) {
    mContext = context;
    this.blog_list = blog_list;
}

@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {

    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.blog_list_item, parent, false);
    firebaseFirestore = FirebaseFirestore.getInstance();
    return new ViewHolder(view);
}

@Override
public void onBindViewHolder(@NonNull final ViewHolder holder, int position) {

    String desc_data = blog_list.get(position).getDesc();
    holder.setDescText(desc_data);


    String user_name = blog_list.get(position).getUser_id();
    holder.setBlogUserName(user_name);

    String image_url = blog_list.get(position).getImage_url();
    holder.setBlogImage(image_url);

    final String message_doc = blog_list.get(position).getMessage_doc();


    /*
    long millisecond = blog_list.get(position).getTimestamp().getTime();
    String dateString = DateFormat.format("MM/dd/yyyy", new Date(millisecond)).toString();
    holder.setTime(dateString);
    */


    //  String user_data = blog_list.get(position).getUser_id();
    //  holder.setUserData(user_data);


    holder.parentLayout.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {

            int pos = holder.getAdapterPosition();

            //THIS IS WHAT NEEDS TO GET PASSED
            String id = blog_list.get(pos).getPost_id();

            /*
            //IMPORTANT
            Intent messageDocIntent = new Intent(mContext, BlogRecyclerAdapter.class);
            messageDocIntent.putExtra("EXTRA_SESSION_ID", message_doc);
            mContext.startActivity(messageDocIntent);
            */
            Toast.makeText(mContext, message_doc, Toast.LENGTH_LONG).show();

            // Toast.makeText(mContext, "test " + id, Toast.LENGTH_LONG).show();

            Intent intent = new Intent(mContext, Confirmation_Activity.class);
            mContext.startActivity(intent);


        }
    });

}

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

public class ViewHolder extends RecyclerView.ViewHolder {

    public Context mContext;
    ConstraintLayout parentLayout;
    private View mView;
    private TextView descView;
    private ImageView blogPostView;
    private TextView blogDate;
    private TextView blogUserName;
    private CircleImageView blogUserImage;
    private StorageReference mImageStorage;
    private TextView userName;


    @SuppressLint("ResourceType")
    public ViewHolder(View itemView) {
        super(itemView);
        mView = itemView;
        parentLayout = itemView.findViewById(R.id.Main_Blog_Post);

    }

    public void setDescText(String descText) {
        descView = mView.findViewById(R.id.blog_desc);
        descView.setText(descText);
    }

    public void setUserData(String downloadUrl, String name) {

        mImageStorage = FirebaseStorage.getInstance().getReference();

        mCurrentUser = FirebaseAuth.getInstance().getCurrentUser();
        final String current_uid = mCurrentUser.getUid();

        mUserDatabase = FirebaseDatabase.getInstance().getReference().child("Users").child(current_uid);
        mUserDatabase.keepSynced(true);

        mUserDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {

                String name = Objects.requireNonNull(dataSnapshot.child("name").getValue()).toString();

                StorageReference filepath = mImageStorage.child("profile_images").child(current_uid + (".jpeg"));
                Log.d("heere", "S");

                // This gets the download url async
                filepath.getDownloadUrl().addOnSuccessListener(new OnSuccessListener<Uri>() {
                    @Override
                    public void onSuccess(Uri uri) {

                        //The download url
                        final String downloadUrl =
                                uri.toString();
                        Log.d("tag", downloadUrl);
                        if (!downloadUrl.equals("default")) {

                            //  Glide.with(getApplicationContext()).load(downloadUrl).into(mDisplayImage);
                            Glide.with(itemView.getContext()).load(downloadUrl).into(blogUserImage);

                        }
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        // Toast.makeText(getApplicationContext(), "Something went wrong", Toast.LENGTH_SHORT).show();
                    }
                });
                //Toast.makeText(getApplicationContext(), image, Toast.LENGTH_SHORT).show();

                Log.d("value", dataSnapshot.getValue().toString());
                Log.d("key", dataSnapshot.getKey());
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });


    }

    public void setTime(String date) {

        blogDate = mView.findViewById(R.id.blog_date);
        blogDate.setText(date);

    }

    public void setBlogImage(final String downloadUri) {

        blogPostView = mView.findViewById(R.id.blog_image);
        Glide.with(itemView.getContext()).load(downloadUri).into(blogPostView);


    }

    public void setBlogUserName(String userName) {
        blogUserName = mView.findViewById(R.id.blog_user_name);
        blogUserName.setText(userName);
    }


    }
}

如果您能为我指明正确的方向，那将不胜感激

当前问题

适配器

    @Override
public void onBindViewHolder(@NonNull final ViewHolder holder, int position) {

    String desc_data = blog_list.get(position).getDesc();
    holder.setDescText(desc_data);


    String user_name = blog_list.get(position).getUser_id();
    holder.setBlogUserName(user_name);

    String image_url = blog_list.get(position).getImage_url();
    holder.setBlogImage(image_url);

    final String message_doc = blog_list.get(position).getMessage_doc();


    holder.parentLayout.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            int pos = holder.getAdapterPosition();

            Toast.makeText(mContext, message_doc, Toast.LENGTH_LONG).show();

            Intent intent = new Intent(mContext, Confirmation_Activity.class);
            intent.putExtra("Message_ID", blog_list.get(pos).getMessage_doc());
            mContext.startActivity(intent);

        }
    });

}

活动正在接收

    @Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.chat_activity);

    mFirebaseDatabase = FirebaseDatabase.getInstance();
    mMessagedatabaseReference = 

mFirebaseDatabase.getReference().child(messageID());
....



    public String messageID(){
    String id = getIntent().getStringExtra("Message_ID");
    return id;
}

如果我在适配器活动中调试应用，则Message_Id等于firebase中的值，但是当我启动新活动时，应用崩溃并

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.debateapp/com.example.android.debateapp.ChatActivity}: java.lang.NullPointerException: Can't pass null for argument 'pathString' in child()

，错误指向mMessagedatabaseReference

Answer 1

根据您的代码，您想将一个ID发送给Confirmation_Activity.class，然后您就可以像这样发送一个捆绑包：-

来自适配器：-

Intent intent = new Intent(mContext, Confirmation_Activity.class);
intent.putExtra("id", blog_list.get(position).getPost_id())
mContext.startActivity(intent);

在您的Confirmation_Activity.class中：-

String id = getIntent().getStringExtras("id");

Answer 2

原来我正在尝试将Firestore ID实时传递

将数据从回收站适配器传递到活动

2 个答案: