滚动时在 recyclerView 中取消选中复选框

Question

I have a cursor which retrieves a list of ingredients and populates an adapter, which is then assigned to a recycler View having checkboxes. The problem I've got is that, when I check a set of checkboxes and scroll down, the ones selected from the top, get deselected and vice versa, or in some instances, if I select three from the top, three from the bottom get selected. I need to make sure that, initially nothing is selected, and even if I scroll up and down, the ones selected should remain selected and need to keep track of.

Here is the list which is scrolable.

Here is my code:

class RecipeDetailCursorAdapter extends CursorRecyclerViewAdapter<RecyclerView.ViewHolder> {

    private int mBrownColor;
    private int mGreenColor;
    private int mCheckItems;
    private ItemsCheckedCallback mCheckedCallback;

    RecipeDetailCursorAdapter(Context context, Cursor cursor, ItemsCheckedCallback callback) {
        super(context, cursor);
        mCheckedCallback = callback;
        mBrownColor = ContextCompat.getColor(mContext, R.color.colorTextBrown);
        mGreenColor = ContextCompat.getColor(mContext, R.color.colorTextGreen);
        mCheckItems = 0;
    }

    @Override
    public void onBindViewHolder(RecyclerView.ViewHolder viewHolder, Cursor cursor) {
        String taskName = cursor.getString(cursor.getColumnIndexOrThrow(MascotHelper.RecipeTask.NAME));
        ((RecipeTaskHolder) viewHolder).bindView(taskName);
    }

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View v = LayoutInflater.from(parent.getContext())
                .inflate(R.layout.recipe_task_item, parent, false);
        return new RecipeTaskHolder(v);
    }


    private class RecipeTaskHolder extends RecyclerView.ViewHolder
            implements SmoothCheckBox.OnCheckedChangeListener {

        SmoothCheckBox taskBox;
        TextView recipeComponentName;


        RecipeTaskHolder(View v) {
            super(v);
            taskBox = (SmoothCheckBox) v.findViewById(R.id.recipe_task_box);
            recipeComponentName = (TextView) v.findViewById(R.id.recipe_component_name);
            taskBox.setOnCheckedChangeListener(this);
        }


        void bindView(String task) {
            recipeComponentName.setText(task);
        }

        @Override
        public void onCheckedChanged(SmoothCheckBox smoothCheckBox, boolean b) {
            if (smoothCheckBox.isChecked()) {
                recipeComponentName.setTextColor(mBrownColor);
                mCheckItems++;
            } else {
                recipeComponentName.setTextColor(mGreenColor);
                mCheckItems--;
            }


            if (mCheckItems == getItemCount()) {
                //Toast.makeText(mContext, "All items are checked", Toast.LENGTH_SHORT).show();
                mCheckedCallback.onAllItemChecked(true);
            } else {
                mCheckedCallback.onAllItemChecked(false);
            }
        }
    }


    interface ItemsCheckedCallback {
        void onAllItemChecked(boolean status);
    }
}

Any ideas or suggestions would be appreciated.

Answer 1

RecyclerView removes (recycles) the unseen views from the layout on scrolling, this is the basic behavior of recyclerView in order to reduce memory use.

When a view with a checkbox is recycled, a checked checkbox gets unchecked and if it has a listener, the listener gets called.

You can remove the listener from the view when it is recycled. Just override the onViewRecycled method.

    @Override
    public void onViewRecycled(@NonNull MyViewHolder holder) {
        holder.checkBox.setOnCheckedChangeListener(null);
        super.onViewRecycled(holder);
    }

When the view is constructed again, while scrolling, your listener will also be added again.

Answer 2

use logic below on onBindView:

holder.attenCheckBox.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
            @Override
            public void onCheckedChanged(CompoundButton compoundButton, boolean b) {
                if (holder.attenCheckBox.isChecked())
                    dataModel.setChecked(true);
                else
                    dataModel.setChecked(false);
            }
        });

        if (dataModel.getChecked())
            holder.attenCheckBox.setChecked(true);
        else
            holder.attenCheckBox.setChecked(false);
        holder.checkboxLinearLayout.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (holder.attenCheckBox.isChecked())
                    holder.attenCheckBox.setChecked(false);
                else
                    holder.attenCheckBox.setChecked(true);
            }
        });

Explanation:

• Recycle view inflate eveytime when you scroll down or up.
• you need to store a flag in the data pojo to keep track of check status
• using that flag with setOnCheckedChangeListener will enable you to have you checked enable/disable . Make sure you put flag after listener.

Answer 3

@Override
public void onBindViewHolder(MyViewHolder holder,final int position) {
   final ClassName object = objectList.get(position);
    object.checkBox.setOnCheckedChangeListener(null);
    object.checkBox.setChecked(false);
    object.checkBox.setOnCheckedChangeListener(new android.widget.CompoundButton.OnCheckedChangeListener() {
        public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            object.setChecked(isChecked);
        }
    });
}

This continuously binds the views and keeps your checked positions and keeps checking them again and again when ever the view binds.

Hope this helps you.