recyclerView更新list使用notifyDataSetChanged后没有反应的坑

先看adapter类

public class ControlPersonAdapter extends RecyclerView.Adapter {

    private List controlPerson;
    private Context context;

    static class ViewHolder extends RecyclerView.ViewHolder{
        TextView name;
        TextView number;
        TextView commandTitle;
        TextView command;
        TextView startTime;
        TextView endTime;
        Button edit,delete;

        public ViewHolder(View view) {
            super(view);
            name = (TextView)view.findViewById(R.id.name);
            number = (TextView)view.findViewById(R.id.number);
            commandTitle = (TextView)view.findViewById(R.id.command_title);
            command = (TextView)view.findViewById(R.id.command);
            startTime = (TextView)view.findViewById(R.id.start_time);
            endTime = (TextView)view.findViewById(R.id.end_time);
            edit = (Button)view.findViewById(R.id.edit);
            delete = (Button)view.findViewById(R.id.delete);
        }
    }

    public ControlPersonAdapter(List controlPerson){
        this.controlPerson = controlPerson;
    }

//    public void setList(List controlPerson){
//        this.controlPerson = controlPerson;
//    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_control,parent,false);
        context = parent.getContext();
        ViewHolder holder = new ViewHolder(view);
        holder.itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

            }
        });
        return  holder;
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        holder.name.setText(controlPerson.get(position).name);
        holder.number.setText(controlPerson.get(position).number);
        holder.command.setText(controlPerson.get(position).command);
        holder.startTime.setText(controlPerson.get(position).startTime);
        holder.endTime.setText(controlPerson.get(position).endTime);
        if(controlPerson.get(position).isInControl){
            holder.command.setTextColor(ContextCompat.getColor(context,R.color.car_normal));
            holder.commandTitle.setTextColor(ContextCompat.getColor(context,R.color.car_normal));
        }
        holder.edit.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //todo getong 26367 这里要打开新的界面编辑
                Toast.makeText(context,"编辑",Toast.LENGTH_SHORT).show();
            }
        });
        holder.delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                //todo getong 26367 做删除
                Toast.makeText(context,"删除",Toast.LENGTH_SHORT).show();
            }
        });
    }


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


}

 

 我们初始化adapter的代码：

adapter = new ControlPersonAdapter(controlPersonList);
        recyclerView.setAdapter(adapter);

 

刷新dapter的代码：

    private void initPerson() {
//        controlPersonList.addAll(SharedPreferencesUtil.readControlPerson(getActivity()));//正确方法
        controlPersonList = SharedPreferencesUtil.readControlPerson(getActivity());
//        adapter.setList(controlPersonList);//很蠢的解决方法
        adapter.notifyDataSetChanged();
        if(controlPersonList.size() == 0){
            nullRecord.setVisibility(View.VISIBLE);
            recyclerView.setVisibility(View.GONE);
        }else {
            nullRecord.setVisibility(View.GONE);
            recyclerView.setVisibility(View.VISIBLE);
        }
    }

理论上从SharedPreferencesUtil中读取值再赋给controlPersonList后，使用adapter.notifyDataSetChanged()刷新一下没问题的，然后我就打断点观察。

 

从SharedPreferencesUtil读取前：

 读取后：

可以看到的是fragment中的变量controlPersonList变化了，但是adapter中的controlPerson没变。理论上两者是动态绑定的，指向同一块地址的，现在出现了指向地址不一样的情况，为刷新失败的原因。

 

读源码：

public void setAdapter(Adapter adapter) {
        // bail out if layout is frozen
        setLayoutFrozen(false);
        setAdapterInternal(adapter, false, true);
        requestLayout();
    }




private void setAdapterInternal(Adapter adapter, boolean compatibleWithPrevious,
            boolean removeAndRecycleViews) {
        if (mAdapter != null) {
            mAdapter.unregisterAdapterDataObserver(mObserver);
            mAdapter.onDetachedFromRecyclerView(this);
        }
        if (!compatibleWithPrevious || removeAndRecycleViews) {
            removeAndRecycleViews();
        }
        mAdapterHelper.reset();
        final Adapter oldAdapter = mAdapter;
        mAdapter = adapter;
        if (adapter != null) {
            adapter.registerAdapterDataObserver(mObserver);
            adapter.onAttachedToRecyclerView(this);
        }
        if (mLayout != null) {
            mLayout.onAdapterChanged(oldAdapter, mAdapter);
        }
        mRecycler.onAdapterChanged(oldAdapter, mAdapter, compatibleWithPrevious);
        mState.mStructureChanged = true;
        setDataSetChangedAfterLayout();
    }

可见，在setadapter时候添加了一个mObserver观察者。

private class RecyclerViewDataObserver extends AdapterDataObserver {
        RecyclerViewDataObserver() {
        }

        @Override
        public void onChanged() {
            assertNotInLayoutOrScroll(null);
            mState.mStructureChanged = true;

            setDataSetChangedAfterLayout();
            if (!mAdapterHelper.hasPendingUpdates()) {
                requestLayout();
            }
        }

        @Override
        public void onItemRangeChanged(int positionStart, int itemCount, Object payload) {
            assertNotInLayoutOrScroll(null);
            if (mAdapterHelper.onItemRangeChanged(positionStart, itemCount, payload)) {
                triggerUpdateProcessor();
            }
        }

        @Override
        public void onItemRangeInserted(int positionStart, int itemCount) {
            assertNotInLayoutOrScroll(null);
            if (mAdapterHelper.onItemRangeInserted(positionStart, itemCount)) {
                triggerUpdateProcessor();
            }
        }

        @Override
        public void onItemRangeRemoved(int positionStart, int itemCount) {
            assertNotInLayoutOrScroll(null);
            if (mAdapterHelper.onItemRangeRemoved(positionStart, itemCount)) {
                triggerUpdateProcessor();
            }
        }

        @Override
        public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
            assertNotInLayoutOrScroll(null);
            if (mAdapterHelper.onItemRangeMoved(fromPosition, toPosition, itemCount)) {
                triggerUpdateProcessor();
            }
        }

        void triggerUpdateProcessor() {
            if (POST_UPDATES_ON_ANIMATION && mHasFixedSize && mIsAttached) {
                ViewCompat.postOnAnimation(RecyclerView.this, mUpdateChildViewsRunnable);
            } else {
                mAdapterUpdateDuringMeasure = true;
                requestLayout();
            }
        }
    }

再通过观察者类可以发现对item的更新插入都是这里观察者来实现的，观察者观察的是adapter指向的内容，具体也就是adapter中的list，list的有了新的值，但是原来的指向地址的值还没变，所以刷新就无效了。

图示：

oberserber永远观察的都是地址0x0001上的数据。现在list是有值了，但是地址变了。调用notifyDataSetChanged当前没有用了。

 

 

解决：

刷新dapter的代码中被我注掉的部分

        controlPersonList.addAll(SharedPreferencesUtil.readControlPerson(getActivity()));
        adapter.notifyDataSetChanged();

 这样就可以把数据放到list1的位置上。

 

另一行被注掉的方式也能实现更新，去adapter中写一个setlist方法，重新去setList，但是太过愚蠢了。