如何在回收站视图中显示多个视图？

Question

我试图了解如何根据对象上的一些信息轻松地告诉两个不同的视图被膨胀...

我的设置是这样的，但我一直因为这个错误而崩溃：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setTypeface(android.graphics.Typeface)' on a null object reference

指向这条线：

myViewHolder.commentUsername.setTypeface(boldTypeface);

这是我的适配器：

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

    private List<DatabaseComment> dbCommentsList;
    private DatabaseHelper db;
    private Context context;
    private Typeface typeFace, italicTypeface, boldTypeface;


    public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
        public TextView commentUsername, commentUserMsg, commentUserDate, commentUserRemove;
        public ImageView emojiIcon;


        public MyViewHolder(View view) {
            super(view);
            commentUsername = (TextView) view.findViewById(R.id.userAdapterUsername);
            commentUserMsg = (TextView) view.findViewById(R.id.commentUserMsg);
            commentUserDate = (TextView) view.findViewById(R.id.commentUserDate);
            commentUserRemove = (TextView) view.findViewById(R.id.commentUserRemove);
            emojiIcon = (ImageView) view.findViewById(R.id.emojiIcon);
            Log.d(Constants.DEBUG, "IN MY VIEW HOLDER");

            view.setOnClickListener(this);
            commentUserRemove.setOnClickListener(this);

        }

        @Override
        public void onClick(View v) {
            if (mOnEntryClickListener != null) {
                Log.d(Constants.DEBUG, "IN On click");
                mOnEntryClickListener.onEntryClick(v, getAdapterPosition());

            }
        }
    }
    private static OnEntryClickListener mOnEntryClickListener;

    public interface OnEntryClickListener {
        void onEntryClick(View view, int position);
    }

    public void setOnEntryClickListener(OnEntryClickListener onEntryClickListener) {
        mOnEntryClickListener = onEntryClickListener;
    }


    public class MyFeatureViewHolder extends RecyclerView.ViewHolder {
        public TextView commentCompany, commentCompanyMsg, commentCompanyDate;
        public ImageView emojiIcon;


            public MyFeatureViewHolder(View view) {
            super(view);
                commentCompany = (TextView) view.findViewById(R.id.commentCompany);
                commentCompanyMsg = (TextView) view.findViewById(R.id.commentCompanyMsg);
                commentCompanyDate = (TextView) view.findViewById(R.id.commentCompanyDate);
                emojiIcon = (ImageView) view.findViewById(R.id.emojiIcon);
                Log.d(Constants.DEBUG, "IN MY VIEW HOLDER");


        }


    }

    public CommentsAdapter(Context mContext, List<DatabaseComment> comments, Typeface myTypeface, Typeface myTypefaceItalic, Typeface myTypefaceBold) {
        context = mContext;
        db = new DatabaseHelper(context);
        dbCommentsList = comments;
        typeFace = myTypeface;
        italicTypeface = myTypefaceItalic;
        boldTypeface = myTypefaceBold;
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        switch (viewType){
            case 0:
                return new MyFeatureViewHolder(LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.comment_business_item, parent, false)); 
            case 1:
                return new MyFeatureViewHolder(LayoutInflater.from(parent.getContext())
                        .inflate(R.layout.comment_user_item, parent, false));   
        }
        return new MyViewHolder(LayoutInflater.from(parent.getContext())
                .inflate(R.layout.comment_user_item, parent, false));


    }



    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {

        //int pos = getItemViewType(position);

        //is a business comment
        if(dbCommentsList.get(position).getIsType() == 0) {


            MyFeatureViewHolder featureViewHolder = (MyFeatureViewHolder) holder;

            DatabaseComment dbComment = dbCommentsList.get(position);

            featureViewHolder.commentCompany.setTypeface(boldTypeface);
            featureViewHolder.commentCompanyMsg.setTypeface(typeFace);
            featureViewHolder.commentCompanyDate.setTypeface(italicTypeface);

            featureViewHolder.commentCompany.setText(dbComment.getUsername());
            featureViewHolder.commentCompanyMsg.setText(dbComment.getCommentText());

            Calendar date = Calendar.getInstance();
            date.setTimeInMillis(dbComment.getCommentDate());
            String commentDateTxt = (date.get(Calendar.MONTH) + "." + date.get(Calendar.DAY_OF_MONTH) + "." + date.get(Calendar.YEAR));

            featureViewHolder.commentCompanyDate.setText(commentDateTxt);


            //anything greater than 0 is a user comment
        } else {
            //TODO show x button near viewHolder if isChanged is 1

            MyViewHolder myViewHolder = (MyViewHolder) holder;

            if(dbCommentsList.get(position).getIsChanged() == 1) {
                myViewHolder.commentUserRemove.setVisibility(View.VISIBLE);
            } else {
                myViewHolder.commentUserRemove.setVisibility(View.GONE);
            }

            DatabaseComment dbComment = dbCommentsList.get(position);

            myViewHolder.commentUsername.setTypeface(boldTypeface);
            myViewHolder.commentUserMsg.setTypeface(typeFace);
            myViewHolder.commentUserDate.setTypeface(italicTypeface);

            myViewHolder.commentUsername.setText(dbComment.getUsername());
            myViewHolder.commentUserMsg.setText(dbComment.getCommentText());

            Calendar date = Calendar.getInstance();
            date.setTimeInMillis(dbComment.getCommentDate());
            String commentDateTxt = (date.get(Calendar.MONTH) + "." + date.get(Calendar.DAY_OF_MONTH) + "." + date.get(Calendar.YEAR));

            myViewHolder.commentUserDate.setText(commentDateTxt);

            int[] commentsImageList = new int[]{R.drawable.ic_announcement_black_18dp, R.drawable.ic_announcement_black_18dp, R.drawable.ic_announcement_black_18dp, R.drawable.ic_explore_black_18dp};
            myViewHolder.emojiIcon.setImageResource(commentsImageList[dbComment.getIsType()]);



        }

        //grab more comments
        if(position > (dbCommentsList.size() - 3) && (dbCommentsList.size() % 20) == 0) {
            grabMoreComments();
        }

    }

    private void grabMoreComments() {
        //TODO
        //GRABAPI - OFFSET dbCommentsList.SIZE - IN LIMIT OF 20
    }



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



    @Override
    public int getItemViewType(int position) {
        if(dbCommentsList.get(position).getIsType() == 0) {
            return 0;
        }
        return 1;
    }
}

这是我设置适配器的班级：

private void setupAdapter() {
        commentsAdapter = new CommentsAdapter(this, dbCommentsList, TypeFaceProvider.getTypeFace(this, 0),
                TypeFaceProvider.getTypeFace(this, 1), TypeFaceProvider.getTypeFace(this, 2));
        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getApplicationContext());
        commentsRecyclerView.setLayoutManager(mLayoutManager);
        commentsRecyclerView.setItemAnimator(new DefaultItemAnimator());

        //TODO CHECK THAT CLICKING ON COMMENT BY BUSINESS NOTHING HAPPENS

        commentsAdapter.setOnEntryClickListener(new CommentsAdapter.OnEntryClickListener() {
            @Override
            public void onEntryClick(View view, int position) {
                DatabaseComment comment = dbCommentsList.get(position);
                TextView deleteBtn = (TextView) view.findViewById(R.id.commentUserRemove);
                if(view == deleteBtn) {

                    //used to remove the comment from db and the list
                    db.removeSingleComment(comment);
                    dbCommentsList.remove(position);
                    commentsAdapter.notifyDataSetChanged();

                } else {
                    Toast.makeText(getApplicationContext(), comment.getUsername() + " is selected!", Toast.LENGTH_SHORT).show();
                    takeToUserProfile(dbCommentsList.get(position));
                }
            }
        });




        commentsRecyclerView.setAdapter(commentsAdapter);

        commentsAdapter.notifyDataSetChanged();

    }

所以在适配器中 getItemViewType 没有正确完成......我怎么说如果 cmets isType 为 0 来显示一个视图而其他任何东西都显示另一个视图？

Answer 1

首先，您需要覆盖适配器的getItemViewType，如下所示：（我假设您可以将viewholders 与对象的getType() 方法相匹配。）

@Override
   public int getItemViewType(int position) {
      return items.get(position).getType();
   }

并在您的 onCreateViewHolder 方法中切换类型并返回您的相关视图。

     @Override
       public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
          View view = null;
          switch (viewType) {
              case ITEM_TYPE_A:
                  view = mInflater.inflate(R.layout.your_row_a, parent, false);
                  return new ATypeViewHolder(view);

              case ITEM_TYPE_B:
                  view = mInflater.inflate(R.layout.your_row_b, parent, false);
                  return new BTypeViewHolder(view);
    }
}

Inıt 适配器的 onBindViewHolder 方法。

@Override
   public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
         Item item = items.get(position);
         if(item != null){
              initializeViews(item, holder, position);
         }
}

最后在您的initializeViews 方法中根据您的项目类型投射您的视图并使用它：

private void initializeViews(final Item item, final RecyclerView.ViewHolder viewHolder, final int position) {
     swtich(item.gettype())
     {
        case ITEM_TYPE_A:
            ATypeViewHolder holder = (ATYpeViewHolder)viewHolder;
            // init your views

        case ITEM_TYPE_B:
            BTypeViewHolder holder = (BTypeViewHolder)viewHolder;
            // init your views.
     }
}

不是：你的viewholders必须扩展RecyclerView.ViewHolder

我希望这会对你有所帮助。祝你好运。

Answer 2

根据错误，布局文件 comment_user_item.xml 中似乎缺少 ID 为 R.id.userAdapterUsername 的视图