Question

我希望使用上下文在视图适配器类中获取共享首选项，但它返回null。

我尝试过的是：

如何在getitemviewtype中获取适配器的登录参数？

我编辑了以下代码

任何帮助都会很好

import static android.preference.PreferenceManager.getDefaultSharedPreferences;

public class ChattAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private List<Chatt> moviesList;
     Context context;
public String loginx;
    public TextView title, year, genre;
    public CardView cardViewphoto;
    public ImageView resim;
    private static final int TYPE_ITEM0 = 0;
    private static final int TYPE_ITEM1 = 1;
    SharedPreferences pref;
    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView titlem, yearm, genrem;
        public CardView cardViewphoto;
        public ImageView resim;


        public MyViewHolder(View view) {
            super(view);

            titlem = (TextView) view.findViewById(R.id.title);
            genrem = (TextView) view.findViewById(R.id.genre);
            yearm = (TextView) view.findViewById(R.id.year);
            resim= (ImageView) view.findViewById(R.id.profile_image);

        }

    }
    class ViewHolder0 extends RecyclerView.ViewHolder {
        public TextView title, year, genre;
        public CardView cardViewphoto;
        public ImageView resim;


        public ViewHolder0(View v) {
            super(v);

            title = (TextView) v.findViewById(R.id.titlesender);
            genre = (TextView) v.findViewById(R.id.genresender);
            year = (TextView) v.findViewById(R.id.yearsender);
           // resim= (ImageView) v.findViewById(R.id.profile_image);

        }    }



    public ChattAdapter(List<Chatt> moviesList) {
        this.moviesList = moviesList;
    }





    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        context = parent.getContext();

        pref =PreferenceManager.getDefaultSharedPreferences(context);

        //SharedPreferences sharedPreferences = context.getSharedPreferences("FileName", Context.MODE_PRIVATE);
        loginx = pref.getString("user", null);
        Log.d("prefsss",loginx.toString());
       // login= FirebaseAuth.getInstance().getCurrentUser().toString();
        if (viewType == 1 ){
            return new MyViewHolder(LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_list_row, parent, false));
        }
        else{

            return new ViewHolder0(LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_list_row2, parent, false));

        }

        // View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_list_row, parent, false);


        //return new MyViewHolder(itemView);
    }

    @Override
    public int getItemViewType(int position ) {
        // Here you have to write logic for which position have which type of row and return the same
        Chatt love = moviesList.get(position);
        Log.d("law",love.getTitle().toString());
        Log.d("prefsss",loginx.toString());

        //Log.d("law",login);
        Random r = new Random();
        int i1 = r.nextInt(80 - 65) + 65;
       //  pref =PreferenceManager.getDefaultSharedPreferences(context);

        //SharedPreferences sharedPreferences = context.getSharedPreferences("FileName", Context.MODE_PRIVATE);
       // login = pref.getString("user", null);


        if( love.getTitle().equals(loginx)){

           return 2;
       }else{


           return 1;

       }


    }
    @Override
    public void onBindViewHolder( RecyclerView.ViewHolder holder, int position) {




Log.d("lawtayp",String.valueOf(holder.getItemViewType()) );
            if (holder.getItemViewType()==2){
                ViewHolder0 viewHolder0 = (ViewHolder0)holder;
                Chatt love = moviesList.get(position);

             //   viewHolder0.title.setText(love.getTitle());
              //  viewHolder0.genre.setText(love.getGenre());
                viewHolder0.year.setText(love.getYear());
                // Picasso.with(getClass()).load("http://barronpw.alwaysdata.net/p/"+name+".png").into(cardViewphoto);
               // Picasso.with(context).load("http://barronpw.alwaysdata.net/p/"+love.getTitle() +".png").into(viewHolder0.resim);


            }else{


                // code to populate type 1 view here
                MyViewHolder myviewholder = (MyViewHolder)holder;
                Chatt love = moviesList.get(position);

                // Chatt love = moviesList.get(position);

               // myviewholder.titlem.setText(love.getTitle());
               // myviewholder.genrem.setText(love.getGenre());
                myviewholder.yearm.setText(love.getYear());
                // Picasso.with(getClass()).load("http://barronpw.alwaysdata.net/p/"+name+".png").into(cardViewphoto);
               Picasso.with(context).load("http://barronpw.alwaysdata.net/p/"+love.getTitle() +"-p.png").into(myviewholder.resim);
            }



            // Code to populate type 0 view here




    }


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

Answer 1

试试这个

public class ChattAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    private List<Chatt> moviesList;
     Context context;
public String loginx;
    public TextView title, year, genre;
    public CardView cardViewphoto;
    public ImageView resim;
    private static final int TYPE_ITEM0 = 0;
    private static final int TYPE_ITEM1 = 1;
    SharedPreferences pref;
    public class MyViewHolder extends RecyclerView.ViewHolder {
        public TextView titlem, yearm, genrem;
        public CardView cardViewphoto;
        public ImageView resim;

public ChattAdapter(Context context){
        this.context = context;
}
....

    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        // context = parent.getContext();

        pref =PreferenceManager.getDefaultSharedPreferences(context);
....

}

Answer 2

问题是应该在应用程序中的上下文，以便可以正确读取共享首选项。一种方法是使用构造函数将activity / fragment的上下文作为附加参数传递给适配器。

Answer 3

制作构造函数：

    public ChattAdpater(Context context){
  prefs = PreferenceManager.getDefaultSharedPreferences(context);
     }

从onCreateViewHolder中删除prefs初始化

无法在View Adapter中获取SharedPreferences返回null

3 个答案: