Strange RecyclerView复选框onCheckChanged行为 [英] Strange RecyclerView Checkbox onCheckChanged Behavior

问题描述

我正在工作，我在 RecyclerView 项目中有checkboxe。我知道其中的一些问题。但是，只有10个项目，没有滚动错误的监听器。

I am working where I have checkboxe inside RecyclerView items. I am aware of some of its issues. But, with only 10 items and no scrolling wrong listener is called.

我有这样的：

private class MyAdapter extends RecyclerView.Adapter<MyViewHodler> {
    ArrayList<String> items;
    ArrayList<String> checkedList = new ArrayList<>();
    ...

    public void onBindViewHolder(final MyViewHolder holder, int position) {
        String item = items.get(position);
        String check = checkedList.get(item);
        if(check != null)
            holder.vChecked.setChecked(true);
        else
            holder.vChecked.setChecked(false);

        ....

        holder.vChecked.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
                @Override
                public void onCheckedChanged(CompoundButton compoundButton, boolean isChecked) {
                    if (isChecked) {
                        checkedList.add(item);
                    } else {
                        checkedList.remove(item);
                    }
                }
    }

}

现在，奇怪的是这个checkedChange我的列表只有10个项目，并且适合在recyclelerview，没有滚动。我从外部更改数据（项目和检查列表），设置新的数据，并调用 myAdapter .notifyDatasetChanged（）

Now, strangely this checkedChange calls are made on different views. I have a list of only 10 items and are fit in the recyclerview, no scrolling. I externally change the data (items and checked list), set the new data and calling myAdapter.notifyDatasetChanged()

此调用将从已选状态中删除一个项目。

This call removes one more item from the checked state.

例如，我有10个项目都被检查。我取消选择1项，并基于它和一些其他计算并调用 myAdapter.notifyDatasetChanged（）。

For example, I have 10 items all checked. I uncheck 1 item, and doing some other calculations based on that and calling myAdapter.notifyDatasetChanged(). It also unchecks one more element from the other 9 items.

因此，即使没有滚动，为什么onCheckedChange侦听器被调用为错误的视图？

So even without scrolling why onCheckedChange listener is called for the wrong view?

推荐答案

我发现了问题。我认为 onBindViewHolder 被调用每个视图来改变数据。但我错了。

I have found out the problem. I thought onBindViewHolder is called for every view to change the data. But I was wrong.

notifyDatasetChanged（）回收屏幕上的所有视图持有者，并从回收视图持有者池中随机选择观看者绑定新数据。因此，当我调用 notifyDatasetChanged 时，视图持有者在不同的位置使用，因此更改了一个项目。

notifyDatasetChanged() recycles all the view holders on screen and from the recycled view holder pool randomly viewholders are picked to bind the new data. So when I called the notifyDatasetChanged, the viewholder was used at the different position, and thus changed one more item.

所以，我将回收器视图的 onViewRecycled 方法中的侦听器删除为null。像这样：

So, I removed the listener to null in onViewRecycled method of the recycler view. Like this:

    @Override
    public void onViewRecycled(MyViewHolder holder) {
        super.onViewRecycled(holder);

        holder.vChecked.setOnCheckedChangeListener(null);
    }

这解决了问题。我知道这一点，但我认为视图持有者被重复使用相同的位置，如果没有滚动。但 onDatasetChanged 回收所有当前使用的视图持有者，并从随机池中再次使用它。

This, did solved the issue. I was aware of this, but I thought viewholders are reused for the same position if there is no scrolling. But onDatasetChanged recycles all currently used view holders and uses it again from the random pool.

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