java - 我的 Recyclerview 加载无限错误

Question

我尝试使用 recyclerview 和改造来构建应用程序，但是当从 JSON 文件加载数据时，我的 recyclerview 会重复无限次，结果相同。

对于样本加载所有可用数据，并在无限重复结果后，这样：

示例图像

普通的：

--------------------
|      Name 1      |
--------------------
|      Name 2      |
--------------------
|      Name 3      |
--------------------

和错误

--------------------
|      Name 1      |
--------------------
|      Name 2      |
--------------------
|      Name 3      |
--------------------
|      Name 1      |
--------------------
|      Name 2      |
--------------------
|      Name 3      |
--------------------
...

下面附上onScrollListener.java

import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;

public abstract class EndlessRecyclerOnScrollListener extends RecyclerView.OnScrollListener {

    private int visibleThreshold = 5;

    private int currentPage = 0;

    private int previousTotalItemCount = 0;

    private boolean loading = true;

    private int startingPageIndex = 0;

    RecyclerView.LayoutManager mLayoutManager;

    public EndlessRecyclerOnScrollListener(LinearLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
    }

    public EndlessRecyclerOnScrollListener(GridLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
        visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
    }

    public EndlessRecyclerOnScrollListener(StaggeredGridLayoutManager layoutManager) {
        this.mLayoutManager = layoutManager;
        visibleThreshold = visibleThreshold * layoutManager.getSpanCount();
    }

    public int getLastVisibleItem(int[] lastVisibleItemPositions) {
        int maxSize = 0;
        for (int i = 0; i < lastVisibleItemPositions.length; i++) {
            if (i == 0) {
                maxSize = lastVisibleItemPositions[i];
            }
            else if (lastVisibleItemPositions[i] > maxSize) {
                maxSize = lastVisibleItemPositions[i];
            }
        }
        return maxSize;
    }


    @Override
    public void onScrolled(RecyclerView view, int dx, int dy) {
        int lastVisibleItemPosition = 0;
        int totalItemCount = mLayoutManager.getItemCount();

        if (mLayoutManager instanceof StaggeredGridLayoutManager) {
            int[] lastVisibleItemPositions = ((StaggeredGridLayoutManager) mLayoutManager).findLastVisibleItemPositions(null);
            // get maximum element within the list
            lastVisibleItemPosition = getLastVisibleItem(lastVisibleItemPositions);
        } else if (mLayoutManager instanceof GridLayoutManager) {
            lastVisibleItemPosition = ((GridLayoutManager) mLayoutManager).findLastVisibleItemPosition();
        } else if (mLayoutManager instanceof LinearLayoutManager) {
            lastVisibleItemPosition = ((LinearLayoutManager) mLayoutManager).findLastVisibleItemPosition();
        }

        if (totalItemCount < previousTotalItemCount) {
            this.currentPage = this.startingPageIndex;
            this.previousTotalItemCount = totalItemCount;
            if (totalItemCount == 0) {
                this.loading = true;
            }
        }

        if (loading && (totalItemCount > previousTotalItemCount)) {
            loading = false;
            previousTotalItemCount = totalItemCount;
        }

        if (!loading && (lastVisibleItemPosition + visibleThreshold) > totalItemCount) {
            currentPage++;
            onLoadMore(currentPage, totalItemCount, view);
            loading = true;
        }
    }


    public void resetState() {
        this.currentPage = this.startingPageIndex;
        this.previousTotalItemCount = 0;
        this.loading = true;
    }

    // Defines the process for actually loading more data based on page
    public abstract void onLoadMore(int page, int totalItemsCount, RecyclerView view);

}

这是我在 MainActivity 中的代码OnCreate

recyclerView.addOnScrollListener(new EndlessRecyclerOnScrollListener((LinearLayoutManager) mLayoutManager) {
            @Override
            public void onLoadMore(int page, int totalItemsCount, RecyclerView view) {
                getInbox();
            }
        });

下面加载数据并将消息列表构建getInbox到MainActivity

private void getInbox() {
    swipeRefreshLayout.setRefreshing(true);

    Map<String, String> datos = new HashMap<>();
    datos.put("ruta", user.getRuta());
    datos.put("jornada", user.getJornada());
    datos.put("id_ppl", user.getId_ppl());
    datos.put("placa", user.getPlaca());
    //datos.put("page", String.valueOf(index));

    Call<List<Message>> call = apiService.getInbox(datos)  ;

    call.enqueue(new Callback<List<Message>>() {

        @Override
        public void onResponse(Call<List<Message>> call,  retrofit2.Response<List<Message>> response) {

            // TODO - avoid looping
            for ( Message message : response.body()) {
                // generate a random color
                message.setColor(getRandomMaterialColor("400"));
                messages.add(message);
            }

            mAdapter.notifyDataSetChanged();

        }

        @Override
        public void onFailure(Call<List<Message>> call, Throwable t) {
            Toast.makeText(getApplicationContext(), "Unable to fetch json: " + t.getMessage(), Toast.LENGTH_LONG).show();
            swipeRefreshLayout.setRefreshing(false);
        }
    });

}

这是我的adapter.java

public class MessagesAdapter extends RecyclerView.Adapter<MessagesAdapter.MyViewHolder> {
    private Context mContext;
    private List<Message> messages;
    private MessageAdapterListener listener;
    private SparseBooleanArray selectedItems;

    // array used to perform multiple animation at once
    private SparseBooleanArray animationItemsIndex;
    private boolean reverseAllAnimations = false;

    // index is used to animate only the selected row
    // dirty fix, find a better solution
    private static int currentSelectedIndex = -1;



    public class MyViewHolder extends RecyclerView.ViewHolder implements View.OnLongClickListener {
        public TextView from, subject, message, iconText, timestamp;
        public ImageView iconImp, imgProfile;
        public LinearLayout messageContainer;
        public RelativeLayout iconContainer, iconBack, iconFront;

        public MyViewHolder(View view) {
            super(view);
            from = view.findViewById(R.id.from);
            subject = view.findViewById(R.id.txt_primary);
            message = view.findViewById(R.id.txt_secondary);
            iconText = view.findViewById(R.id.icon_text);
            timestamp = view.findViewById(R.id.timestamp);
            iconBack = view.findViewById(R.id.icon_back);
            iconFront = view.findViewById(R.id.icon_front);
            iconImp = view.findViewById(R.id.icon_star);
            imgProfile = view.findViewById(R.id.icon_profile);
            messageContainer = view.findViewById(R.id.message_container);
            iconContainer = view.findViewById(R.id.icon_container);
            view.setOnLongClickListener(this);
        }

        @Override
        public boolean onLongClick(View view) {
            listener.onRowLongClicked(getAdapterPosition());
            view.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS);
            return true;
        }
    }


    public MessagesAdapter(Context mContext, List<Message> messages, MessageAdapterListener listener) {
        this.mContext = mContext;
        this.messages = messages;
        this.listener = listener;
        selectedItems = new SparseBooleanArray();
        animationItemsIndex = new SparseBooleanArray();
    }

    @Override
    public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
         View itemView;

         itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.message_list_row, parent, false);

        return new MyViewHolder(itemView);
    }



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

        Message message = messages.get(position);

        // displaying text view data
        holder.from.setText(message.getFrom());
        holder.subject.setText(message.getSubject());
        holder.message.setText(message.getMessage());
        holder.timestamp.setText(message.getTimestamp());

        // displaying the first letter of From in icon text
        holder.iconText.setText(message.getFrom().substring(0, 1));

        // change the row state to activated
        holder.itemView.setActivated(selectedItems.get(position, false));

        // change the font style depending on message read status
        applyReadStatus(holder, message);

        // handle message star
        applyImportant(holder, message);

        // handle icon animation
        applyIconAnimation(holder, position);

        // display profile image
        applyProfilePicture(holder, message);

        // apply click events
        applyClickEvents(holder, position);




    }

    private void applyClickEvents(MyViewHolder holder, final int position) {
        holder.iconContainer.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                listener.onIconClicked(position);
            }
        });

        holder.iconImp.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                listener.onIconImportantClicked(position);
            }
        });

        holder.messageContainer.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                listener.onMessageRowClicked(position);
            }
        });

        holder.messageContainer.setOnLongClickListener(new View.OnLongClickListener() {
            @Override
            public boolean onLongClick(View view) {
                listener.onRowLongClicked(position);
                view.performHapticFeedback(HapticFeedbackConstants.LONG_PRESS);
                return true;
            }
        });
    }

    private void applyProfilePicture(MyViewHolder holder, Message message) {
        if (!TextUtils.isEmpty(message.getPicture())) {
            Glide.with(mContext).load(message.getPicture())
                    .thumbnail(0.5f)
                   // .crossFade()
                   // .transform(new CircleTransform(mContext))
                    //.diskCacheStrategy(DiskCacheStrategy.ALL)
                    .into(holder.imgProfile);
            holder.imgProfile.setColorFilter(null);
            holder.iconText.setVisibility(View.GONE);
        } else {
            holder.imgProfile.setImageResource(R.drawable.bg_circle);
            holder.imgProfile.setColorFilter(message.getColor());
            holder.iconText.setVisibility(View.VISIBLE);
        }
    }

    private void applyIconAnimation(MyViewHolder holder, int position) {
        if (selectedItems.get(position, false)) {
            holder.iconFront.setVisibility(View.GONE);
            resetIconYAxis(holder.iconBack);
            holder.iconBack.setVisibility(View.VISIBLE);
            holder.iconBack.setAlpha(1);
            if (currentSelectedIndex == position) {
                FlipAnimator.flipView(mContext, holder.iconBack, holder.iconFront, true);
                resetCurrentIndex();
            }
        } else {
            holder.iconBack.setVisibility(View.GONE);
            resetIconYAxis(holder.iconFront);
            holder.iconFront.setVisibility(View.VISIBLE);
            holder.iconFront.setAlpha(1);
            if ((reverseAllAnimations && animationItemsIndex.get(position, false)) || currentSelectedIndex == position) {
                FlipAnimator.flipView(mContext, holder.iconBack, holder.iconFront, false);
                resetCurrentIndex();
            }
        }
    }


    // As the views will be reused, sometimes the icon appears as
    // flipped because older view is reused. Reset the Y-axis to 0
    private void resetIconYAxis(View view) {
        if (view.getRotationY() != 0) {
            view.setRotationY(0);
        }
    }

    public void resetAnimationIndex() {
        reverseAllAnimations = false;
        animationItemsIndex.clear();
    }

    @Override
    public long getItemId(int position) {
        return messages.get(position).getId();



    }

    private void applyImportant(MyViewHolder holder, Message message) {
        if (message.isImportant()) {
            holder.iconImp.setImageDrawable(ContextCompat.getDrawable(mContext, R.drawable.ic_star_black_24dp));
            holder.iconImp.setColorFilter(ContextCompat.getColor(mContext, R.color.icon_tint_selected));
        } else {
            holder.iconImp.setImageDrawable(ContextCompat.getDrawable(mContext, R.drawable.ic_star_border_black_24dp));
            holder.iconImp.setColorFilter(ContextCompat.getColor(mContext, R.color.icon_tint_normal));
        }
    }

    private void applyReadStatus(MyViewHolder holder, Message message) {
        if (message.isRead()) {
            holder.from.setTypeface(null, Typeface.NORMAL);
            holder.subject.setTypeface(null, Typeface.NORMAL);
            holder.from.setTextColor(ContextCompat.getColor(mContext, R.color.subject));
            holder.subject.setTextColor(ContextCompat.getColor(mContext, R.color.message));
        } else {
            holder.from.setTypeface(null, Typeface.BOLD);
            holder.subject.setTypeface(null, Typeface.BOLD);
            holder.from.setTextColor(ContextCompat.getColor(mContext, R.color.from));
            holder.subject.setTextColor(ContextCompat.getColor(mContext, R.color.subject));
        }
    }

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

    public void toggleSelection(int pos) {
        currentSelectedIndex = pos;
        if (selectedItems.get(pos, false)) {
            selectedItems.delete(pos);
            animationItemsIndex.delete(pos);
        } else {
            selectedItems.put(pos, true);
            animationItemsIndex.put(pos, true);
        }
        notifyItemChanged(pos);
    }

    public void clearSelections() {
        reverseAllAnimations = true;
        selectedItems.clear();
        notifyDataSetChanged();
    }

    public int getSelectedItemCount() {
        return selectedItems.size();
    }

    public List<Integer> getSelectedItems() {
        List<Integer> items =
                new ArrayList<>(selectedItems.size());
        for (int i = 0; i < selectedItems.size(); i++) {
            items.add(selectedItems.keyAt(i));
        }
        return items;
    }

    public void removeData(int position) {
        messages.remove(position);
        resetCurrentIndex();
    }

    private void resetCurrentIndex() {
        currentSelectedIndex = -1;
    }

    public interface MessageAdapterListener {
        void onStatusChanged(String s, int i, Bundle bundle);

        void onProviderEnabled(String s);

        void onProviderDisabled(String s);

        void onIconClicked(int position);

        void onIconImportantClicked(int position);

        void onMessageRowClicked(int position);

        void onRowLongClicked(int position);
    }

我用于构建 Json 的 PHP 文件

$url = "http://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";
$parts = parse_url($url);
$flag = 0;
$page = 1;
if(!empty($_GET)){
    parse_str($parts['query'],$query);
    $page = $query['page'];
    if($page > 1){
        $flag = 1;
    }else{
        $flag = 0;
    }
}
$per_page = 5;
if($flag == 0){
    $qry = "SELECT * FROM registros_not WHERE ruta = '$ruta' AND jornada = '$jornada' AND placa='$placa' AND (id_ppl = '$id_ppl' OR id_ppl = '') ORDER BY fecha_r DESC LIMIT {$per_page}";
}else{
    $page = $page - 1;
    $offset_page = $per_page * $page;
    $qry = "SELECT * FROM registros_not WHERE ruta = '$ruta' AND jornada = '$jornada' AND placa='$placa' AND (id_ppl = '$id_ppl' OR id_ppl = '') ORDER BY fecha_r DESC LIMIT {$per_page} OFFSET {$offset_page}";
}
$res = mysqli_query($con,$qry);
$response = array();

while($row = mysqli_fetch_array($res)){
    array_push($response,array('id'=>$row['idr'],'subject'=>$row['fecha_r'],'isImportant'=>$row['impor_mj'],'from'=>$row['titulo'],'message'=>$row['msj'],'timestamp'=>$row['cel'],'picture'=>$row['picture'],'isRead'=>$row['read_mj']));
}

echo stripslashes(json_encode($response, JSON_UNESCAPED_UNICODE));

我是学生，仍然是菜鸟，谢谢您的帮助。

标签： javaandroid

Answer 1

每次滚动时，getInbox()都会执行该方法。这意味着对 API 进行了调用。所以在onResponse()方法内部，数据第一次被添加到你现有的数组中，然后它显示在：mAdapter.notifyDataSetChanged();然后当你滚动时，这会再次执行，到达的数据会被添加到你现有的消息列表中，messages.add(message);并且然后，它再次显示在此处（您现在拥有的所有数据，即现有项目，+ 新项目）mAdapter.notifyDataSetChanged();：。

要检查它，你可以做一个简单的测试，改变你的onResponse()方法：

 @Override
 public void onResponse(Call<List<Message>> call,  retrofit2.Response<List<Message>> response) {
            messages.clear;
            // TODO - avoid looping
            for ( Message message : response.body()) {
                // generate a random color
                message.setColor(getRandomMaterialColor("400"));
                messages.add(message);
            }

            mAdapter.notifyDataSetChanged();

        }

它应该只显示你下载的数据，每次滚动，所以你知道你一直在添加相同的数据。

为了实现加载额外不同的数据，每次滚动时，都应该向 api 询问“部分”或数据页面。不是所有的数据。