RecyclerView元素更新+异步网络调用

Question

我有一个按预期工作的recyclerview.我在布局中有一个填充列表的按钮.该按钮应该进行异步调用,结果,我改变按钮的外观.这一切都很好.

但是,当我单击按钮并快速向下滚动列表时,异步调用的结果将更新新视图的按钮(代替旧视图的视图).我该如何处理？我可以处理特定视图何时被重用？

更新:

执行异步调用和ui更新的适配器类的代码段.

@Override
public void onBindViewHolder(CommentsViewHolder holder, int position) {
    try {

        Comments comment = comments.get(position);
        holder.bindView(comment,position);

    }
    catch(Exception ex){ex.printStackTrace();}

}

@Override
public int getItemCount() {
    if(comments==null)
    {return 0;}
    return comments.size();
    //return comments.length();
}



public class CommentsViewHolder extends RecyclerView.ViewHolder {
    TextView score ;

    TextView commentText;
    TextView commentTime;
    TextView avatarId;
    ImageButton minusOne;
    ImageButton plusOne;
    ParseObject model;

    public CommentsViewHolder(View itemView) {
        super(itemView);
        //itemView.setBackgroundColor(Color.DKGRAY);
        minusOne =(ImageButton)itemView.findViewById(R.id.decScore);
        plusOne =(ImageButton)itemView.findViewById(R.id.incScore);
        commentText = (TextView)itemView.findViewById(R.id.comment);
        score = (TextView)itemView.findViewById(R.id.commentScore);
        commentTime =(TextView)itemView.findViewById(R.id.commentTime);
        avatarId = (TextView)itemView.findViewById(R.id.ivUserAvatar);
    }
    public void bindView(Comments comment, int position) {


        commentText.setText(comment.getCommentText());

        score.setText(Integer.toString(comment.getScore()));
        String timeText = DateUtils.getRelativeTimeSpanString(  comment.getCreatedAt().getTime(), System.currentTimeMillis(), DateUtils.SECOND_IN_MILLIS).toString();
        timeText = timeText.replace("hours","hrs");
        timeText = timeText.replace("seconds","secs");
        timeText = timeText.replace("minutes","mins");
        commentTime.setText(timeText);
        int commentHandler = comment.getCommenterHandle();
        String commenterNumber = "";
        if(commentHandler==0)
        {
            commenterNumber = "OP";
        }
        else{
            commenterNumber = "#"+commentHandler;
        }
        avatarId.setText( commenterNumber);
        model = comment;

        String choice = "none";
        minusOne.setEnabled(true);
        plusOne.setEnabled(true);
        minusOne.setVisibility(View.VISIBLE);
        plusOne.setVisibility(View.VISIBLE);
        for (ParseObject choiceIter : choices) {


            if ((choiceIter.getParseObject("comment").getObjectId()).equals(comment.getObjectId())) {
                choice = choiceIter.getString("userChoice");

                break;
            }
        }


        Log.i("debug",comment.getCommentText()+" "+comment.getScore()+" "+choice);

        switch (choice) {

            case "plusOne":
                Log.i("darkplus","setting darkplus");
                plusOne.setImageResource(R.drawable.ic_add_circle_black_18dp);
                plusOne.setOnClickListener(reversePlusOneOnClickListener);
                //minusOne.setOnClickListener(minusOneOnClickListener);
                minusOne.setVisibility(View.GONE);
                break;

            case "minusOne":
                Log.i("darkminus","setting darkminus");
                minusOne.setImageResource(R.drawable.ic_remove_circle_black_18dp);
                minusOne.setOnClickListener(reverseMinusOneOnClickListener);
                //plusOne.setOnClickListener(plusOneOnClickListener);
                plusOne.setVisibility(View.GONE);
                break;

            case "none":
                Log.i("darkregular","setting regular");
                minusOne.setImageResource(R.drawable.ic_remove_black_18dp);
                plusOne.setImageResource(R.drawable.ic_add_black_18dp);

                plusOne.setOnClickListener(plusOneOnClickListener);
                minusOne.setOnClickListener(minusOneOnClickListener);
                break;
        }

    }


    View.OnClickListener reversePlusOneOnClickListener = new View.OnClickListener() {

        @Override
        public void onClick(View v) {

            if (!FourUtils.isConnected(v.getContext())) {
                return;
            }

            minusOne.setEnabled(false);
            plusOne.setEnabled(false);
            model.increment("plusOne", -1);
            model.increment("score", -1);

            model.saveEventually(new SaveCallback() {
                @Override
                public void done(ParseException e) {

                    if (e == null) {
                        ParseQuery<ParseObject> query = ParseQuery.getQuery("CommentChoice");
                        query.whereEqualTo("user", ParseUser.getCurrentUser());
                        query.whereEqualTo("comment", model);
                        query.fromPin(Four.COMMENT_CHOICE);
                        query.getFirstInBackground(new GetCallback<ParseObject>() {
                            @Override
                            public void done(ParseObject parseObject, ParseException e) {
                                if (e == null) {
                                    if (parseObject == null) {
                                        parseObject = ParseObject.create("CommentChoice");
                                        parseObject.put("comment", model);
                                        parseObject.put("user", ParseUser.getCurrentUser());

                                    }
                                    parseObject.put("userChoice", "none");
                                    parseObject.pinInBackground(Four.COMMENT_CHOICE, new SaveCallback() {
                                        @Override
                                        public void done(ParseException e) {
                                            if (e == null) {
                                                score.setText(Integer.toString(model.getInt("score")));
                                                //votes.setText((model.getInt("minusOne") + model.getInt("plusOne")) + " votes");

                                                minusOne.setVisibility(View.VISIBLE);
                                                plusOne.setImageResource(R.drawable.ic_add_black_18dp);
                                                plusOne.setOnClickListener(plusOneOnClickListener);
                                                minusOne.setEnabled(true);
                                                plusOne.setEnabled(true);
                                               // minusOne.setOnClickListener(minusOneOnClickListener);
                                                BusProvider.getInstance().post(new NewCommentChoicesAdded());
                                            } else {
                                                e.printStackTrace();
                                            }
                                        }
                                    });
                                }
                                else{e.printStackTrace();}
                            }
                        });
                    } else {
                        e.printStackTrace();
                        Log.i("plus1 error", e.getMessage());
                    }

                }
            });
        }
    };

Answer 1

异步代码完成后,您应该更新数据,而不是视图.更新数据后,告诉适配器数据已更改.RecyclerView会记下这一点并重新呈现您的视图.
使用回收视图(ListView或RecyclerView)时,您无法知道视图所代表的项目.在您的情况下,该视图在异步工作完成之前被回收,并被分配给您的数据的不同项.
所以永远不要修改视图.始终修改数据并通知适配器.bindView应该是您处理这些案例的地方.

Answer 2

来自 Google 的 Chet Haase 在此 DevBytes 视频中讨论了您的确切问题。

简而言之，需要通知框架其中一个视图处于“瞬态”状态。一旦收到通知，框架将不会回收该视图，直到其“瞬态”标志被清除。

在您的情况下，在执行异步操作之前，调用setHasTransientState(true)在异步操作完成时应更改的子视图。在您显式调用该视图之前，该视图不会被回收setHasTransientState(false)。

无关：

看起来您可能正在从后台线程操作 UI 元素。不要那样做！如果您可以参考，Activity请改用其runOnUiThread(Runnable action)API。如果获取引用Activity很困难，您可以获取 UI 线程Handler并使用其post(Runnable action)API。