Android中点击CardView切换背景色并持久化的问题求助

点击Card时背景色有时变化有时不变化，修改后的颜色经常无法保留。想要实现类似Facebook通知页面的效果，通过卡片颜色变化标记已读通知，但Adapter类存在问题。尝试用SharedPreferences保存颜色状态，但未达到预期效果，推测问题出在切换逻辑上。无Android开发专业经验，应用已进入最终阶段，急需解决。

原Adapter代码：

public class PyqAdapter extends RecyclerView.Adapter<PyqAdapter.ViewHolder> {
    private final Context mCtx;
    private final List<PyqModel> pyqModelList;
    private final int defaultBackgroundColor;
    private final int selectedBackgroundColor;
    private final Set<Integer> selectedPositions;

    private static final String PREFS_NAME = "PyqAllItems";
    private static final String SELECTED_ITEMS_KEY = "PyqSelectedItems";

    public PyqAdapter(Context mCtx, List<PyqModel> pyqModelList) {
        if (mCtx == null) {
            throw new IllegalArgumentException("Context cannot be null");
        }
        this.mCtx = mCtx;
        this.pyqModelList = pyqModelList;
        this.selectedPositions = new HashSet<>();

        // Load colors based on the current theme
        Resources res = mCtx.getResources();
        int nightModeFlags = res.getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
        if (nightModeFlags == Configuration.UI_MODE_NIGHT_YES) {
            defaultBackgroundColor = ContextCompat.getColor(mCtx, R.color.defaultBackgroundDark);
            selectedBackgroundColor = ContextCompat.getColor(mCtx, R.color.selectedBackgroundDark);
        } else {
            defaultBackgroundColor = ContextCompat.getColor(mCtx, R.color.defaultBackgroundLight);
            selectedBackgroundColor = ContextCompat.getColor(mCtx, R.color.selectedBackgroundLight);
        }

        // Load selected states from SharedPreferences
        SharedPreferences prefs = mCtx.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
        Set<String> selectedItems = prefs.getStringSet(SELECTED_ITEMS_KEY, new HashSet<>());
        for (String position : selectedItems) {
            selectedPositions.add(Integer.parseInt(position));
        }

        // Set selection state on models based on loaded positions
        for (int i = 0; i < pyqModelList.size(); i++) {
            PyqModel model = pyqModelList.get(i);
            model.setSelected(selectedPositions.contains(i));
        }
    }
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        View view = inflater.inflate(R.layout.pyq_rv_layout, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        final PyqModel temp = pyqModelList.get(position);

        // Set text views
        holder.textView.setText(temp.getPdfName());
        holder.serialNumber.setText(String.valueOf(position + 1));
        holder.pyqTopics.setText(temp.getPyqTopics());

        // Use holder.getAdapterPosition() to get the current position
        int adapterPosition = holder.getAdapterPosition();
        if (adapterPosition == RecyclerView.NO_POSITION) {
            return;
        }

        // Set background color based on selection state
        if (temp.isSelected()) {
            holder.cardView.setCardBackgroundColor(selectedBackgroundColor);
        } else {
            holder.cardView.setCardBackgroundColor(defaultBackgroundColor);
        }

        holder.cardView.setOnClickListener(v -> {
            SharedPreferences prefs = mCtx.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
            SharedPreferences.Editor editor = prefs.edit();
            Set<String> selectedItems = new HashSet<>();
            for (int pos : selectedPositions) {
                selectedItems.add(String.valueOf(pos));
            }
            selectedPositions.add(adapterPosition);
            editor.putStringSet(SELECTED_ITEMS_KEY, selectedItems);
            // Notify adapter to refresh views
            notifyItemChanged(adapterPosition);
            editor.apply();

            // Launch ViewPdf activity
            Intent i = new Intent(holder.cardView.getContext(), ViewPdf.class);
            i.putExtra("pdfName", temp.getPdfName());
            i.putExtra("pdfUrl", temp.getPdfUri());
            i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
            holder.cardView.getContext().startActivity(i);
        });
    }

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

    public static class ViewHolder extends RecyclerView.ViewHolder {
        CardView cardView;
        TextView textView, serialNumber, pyqTopics;

        public ViewHolder(View itemView) {
            super(itemView);
            cardView = itemView.findViewById(R.id.pyqCardView);
            textView = itemView.findViewById(R.id.pyqTitle);
            serialNumber = itemView.findViewById(R.id.serialNumber);
            pyqTopics = itemView.findViewById(R.id.pyqTopics);
        }
    }
}

代码存在3个核心问题导致状态异常：

• 点击逻辑顺序错误：先导出旧集合再添加新位置，导致存储的是未更新的数据
• 未同步更新模型状态：修改selectedPositions后没有更新PyqModel的selected属性，视图绑定会读取旧状态
• 依赖列表位置标记：列表排序、增删会导致位置失效，状态对应关系错乱

public class PyqAdapter extends RecyclerView.Adapter<PyqAdapter.ViewHolder> {
    private final Context mCtx;
    private final List<PyqModel> pyqModelList;
    private final int defaultBackgroundColor;
    private final int selectedBackgroundColor;
    // 改用模型唯一ID存储已读状态，避免位置变化导致错误
    private final Set<String> readItemIds;

    private static final String PREFS_NAME = "PyqAllItems";
    private static final String READ_ITEMS_KEY = "PyqReadItems";

    public PyqAdapter(Context mCtx, List<PyqModel> pyqModelList) {
        if (mCtx == null) {
            throw new IllegalArgumentException("Context cannot be null");
        }
        this.mCtx = mCtx;
        this.pyqModelList = pyqModelList;
        this.readItemIds = new HashSet<>();

        // 加载主题对应颜色
        Resources res = mCtx.getResources();
        int nightModeFlags = res.getConfiguration().uiMode & Configuration.UI_MODE_NIGHT_MASK;
        if (nightModeFlags == Configuration.UI_MODE_NIGHT_YES) {
            defaultBackgroundColor = ContextCompat.getColor(mCtx, R.color.defaultBackgroundDark);
            selectedBackgroundColor = ContextCompat.getColor(mCtx, R.color.selectedBackgroundDark);
        } else {
            defaultBackgroundColor = ContextCompat.getColor(mCtx, R.color.defaultBackgroundLight);
            selectedBackgroundColor = ContextCompat.getColor(mCtx, R.color.selectedBackgroundLight);
        }

        // 从SharedPreferences加载已读状态
        SharedPreferences prefs = mCtx.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
        Set<String> savedReadItems = prefs.getStringSet(READ_ITEMS_KEY, new HashSet<>());
        readItemIds.addAll(savedReadItems);

        // 同步模型的已读状态
        for (PyqModel model : pyqModelList) {
            model.setSelected(readItemIds.contains(model.getId()));
        }
    }

    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        LayoutInflater inflater = LayoutInflater.from(parent.getContext());
        View view = inflater.inflate(R.layout.pyq_rv_layout, parent, false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        final PyqModel temp = pyqModelList.get(position);

        // 设置文本内容
        holder.textView.setText(temp.getPdfName());
        holder.serialNumber.setText(String.valueOf(position + 1));
        holder.pyqTopics.setText(temp.getPyqTopics());

        // 根据模型状态设置背景色
        holder.cardView.setCardBackgroundColor(temp.isSelected() ? selectedBackgroundColor : defaultBackgroundColor);

        holder.cardView.setOnClickListener(v -> {
            // 未标记已读时才更新状态
            if (!temp.isSelected()) {
                temp.setSelected(true);
                readItemIds.add(temp.getId());

                // 保存到SharedPreferences
                SharedPreferences prefs = mCtx.getSharedPreferences(PREFS_NAME, Context.MODE_PRIVATE);
                SharedPreferences.Editor editor = prefs.edit();
                editor.putStringSet(READ_ITEMS_KEY, readItemIds);
                editor.apply();

                // 刷新当前项视图
                notifyItemChanged(position);
            }

            // 跳转PDF页面
            Intent i = new Intent(v.getContext(), ViewPdf.class);
            i.putExtra("pdfName", temp.getPdfName());
            i.putExtra("pdfUrl", temp.getPdfUri());
            v.getContext().startActivity(i);
        });
    }

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

    public static class ViewHolder extends RecyclerView.ViewHolder {
        CardView cardView;
        TextView textView, serialNumber, pyqTopics;

        public ViewHolder(View itemView) {
            super(itemView);
            cardView = itemView.findViewById(R.id.pyqCardView);
            textView = itemView.findViewById(R.id.pyqTitle);
            serialNumber = itemView.findViewById(R.id.serialNumber);
            pyqTopics = itemView.findViewById(R.id.pyqTopics);
        }
    }
}

1. 用唯一ID替代列表位置：
   需要在PyqModel类中添加getId()方法（返回每个PDF的唯一标识，比如文件名或服务器ID），避免列表数据变化导致状态错乱。示例PyqModel补充代码：

   public class PyqModel {
       private String id;
       private boolean isSelected;
       // 其他原有字段
   
       public String getId() { return id; }
       public void setId(String id) { this.id = id; }
       public boolean isSelected() { return isSelected; }
       public void setSelected(boolean selected) { isSelected = selected; }
       // 其他原有getter/setter
   }
   

2. 修正点击逻辑顺序：
   先更新模型状态和集合，再保存到SharedPreferences，确保存储的是最新数据。
3. 简化视图绑定逻辑：
   移除冗余的adapterPosition判断，直接使用onBindViewHolder的position参数，同步模型状态与视图显示。

内容的提问来源于stack exchange，提问作者Satish Bodke