NoteActivity

public class NoteAdapter extends BaseAdapter implements Filterable {
    private Context mcontext;
    private List<Note> backList;//用来备份原始数据
    private List<Note>noteList;//这个数据是会改变的，所以要有个变量来备份一下原始数据
    private MyFilter mFilter;
    public NoteAdapter(Context context,List<Note> noteList){
        Log.d("Adapter","adapter_creat");
        this.mcontext=context;
        this.noteList=noteList;
        backList=noteList;
    }

    @Override
    public int getCount() {
        Log.d("Adapter","adapter_noteList.size");
        return noteList.size();
    }

    @Override
    public Object getItem(int position) {
        return noteList.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        Log.d("Adapter","adapter_view");
        SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(mcontext);
        mcontext.setTheme((sharedPreferences.getBoolean("nightMode", false)? R.style.NightTheme: R.style.DayTheme));
        @SuppressLint("ViewHolder") View v=View.inflate(mcontext,R.layout.note_layout,null);
        TextView tv_content=v.findViewById(R.id.tv_content);
        TextView tv_time=v.findViewById(R.id.tv_time);

        String allText=noteList.get(position).getContent();
        tv_content.setText(allText);
        tv_time.setText(noteList.get(position).getTime());
        v.setTag(noteList.get(position).getId());
        return v;
    }

    @Override
    public Filter getFilter() {
        if (mFilter==null){
            mFilter=new MyFilter();
        }
        return mFilter;
    }

    class MyFilter extends Filter {
        //我们在performFiltering(CharSequence charSequence)这个方法中定义过滤规则
        @Override
        protected FilterResults performFiltering(CharSequence charSequence) {
            FilterResults result = new FilterResults();
            List<Note> list;
            if (TextUtils.isEmpty(charSequence)) {//当过滤的关键字为空的时候，我们则显示所有的数据
                list = backList;
            } else {//否则把符合条件的数据对象添加到集合中
                list = new ArrayList<>();
                for (Note note : backList) {
                    if (note.getContent().contains(charSequence)) {
                        list.add(note);
                    }

                }
            }
            result.values = list; //将得到的集合保存到FilterResults的value变量中
            result.count = list.size();//将集合的大小保存到FilterResults的count变量中

            return result;
        }
        //在publishResults方法中告诉适配器更新界面
        @Override
        protected void publishResults(CharSequence charSequence, FilterResults filterResults) {
            noteList = (List<Note>)filterResults.values;
            if (filterResults.count>0){
                notifyDataSetChanged();//通知数据发生了改变
            }else {
                notifyDataSetInvalidated();//通知数据失效
            }
        }
    }

}