android - Activity 恢复时更新 RecyclerView？

Question

我有一个 QuestionActivity我是否在 RecyclerView 中显示问题列表？ .

我在工具栏中有两个 Action

转到下载的文件 Activity 。

去最喜欢的 Activity 。

一切正常，但是当我点击其中一个操作并返回 QuestionActivity 时 RecyclerView无法更新。

所以我需要覆盖 OnResume方法。我的问题是，如何更新 RecyclerView在 onResume方法 。
AdapterRecyclerQuestion代码 :

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

    private Context context;
    private ArrayList<ModelQuestion> questionha;
    private int lastd;


    ////////////////////////////////////////////////////////////
    //================== Constructor   =========================
    ////////////////////////////////////////////////////////////

    public AdapterRecyclerQuestion(Context context, ArrayList<ModelQuestion> questionha) {
        this.context = context;
        this.questionha = questionha;
    }

    ////////////////////////////////////////////////////////////
    //================== view holder  =========================
    ////////////////////////////////////////////////////////////

    public class ViewHolder extends RecyclerView.ViewHolder {
        private TextView txtTitle;
        private TextView txtDesc;
        private TextView txtCntDown;
        private Button btnDownload;
        private ImageView imgAddFav;
        private ProgressBar prgDownload;

        ////////////////////////////////////////////////////////////
        //================== View holder constructor  ==============
        ////////////////////////////////////////////////////////////

        public ViewHolder(View itemView) {
            super(itemView);
            txtTitle = (TextView) itemView.findViewById(R.id.txt_title_question);
            txtDesc = (TextView) itemView.findViewById(R.id.txt_desc_question);
            txtCntDown = (TextView) itemView.findViewById(R.id.txt_cnt_down_question_dy);
            btnDownload = (Button) itemView.findViewById(R.id.btn_down_question);
            imgAddFav = (ImageView) itemView.findViewById(R.id.img_add_to_fav);
            prgDownload = (ProgressBar) itemView.findViewById(R.id.prgDownload);
        }
    }
    ////////////////////////////////////////////////////////////
    //================== on create view holder  ================
    ////////////////////////////////////////////////////////////

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

    ////////////////////////////////////////////////////////////
    //================== on bind view holder  =================
    ////////////////////////////////////////////////////////////

    @Override
    public void onBindViewHolder(final ViewHolder holder, final int position) {


        QuestionDatabaseAdapter questionDatabaseAdapter = new QuestionDatabaseAdapter(holder.itemView.getContext());

        holder.txtTitle.setText(questionha.get(position).getQuestionTitle());
        holder.txtDesc.setText(questionha.get(position).getQuestionDesc());
        holder.txtCntDown.setText(questionha.get(position).getQuestionDownCnt());

        ////////////////////////////////////////////////////////////
        //================== Favorite checking  ====================
        ////////////////////////////////////////////////////////////


        boolean isFavorite = questionDatabaseAdapter.isQuestionFavorite(questionha.get(position).getQuestionId());

        if (isFavorite)

        {
            holder.imgAddFav.setImageResource(R.drawable.ic_favorite_red_700_24dp);
        } else

        {
            holder.imgAddFav.setImageResource(R.drawable.ic_favorite_border_red_a700_24dp);
        }


        ////////////////////////////////////////////////////////////
        //================== img add fav listener  =================
        ////////////////////////////////////////////////////////////

        holder.imgAddFav.setOnClickListener(new View.OnClickListener() {

                                                @Override
                                                public void onClick(View v) {

                                                    QuestionDatabaseAdapter databaseAdapter = new QuestionDatabaseAdapter(v.getContext());
                                                    boolean isFav = databaseAdapter.isQuestionFavorite(questionha.get(position).getQuestionId());

                                                    if (!isFav) {
                                                        Toast.makeText(v.getContext(), "به لیست علاقه مندی ها اضافه شد", Toast.LENGTH_SHORT).show();
                                                        holder.imgAddFav.setImageResource(R.drawable.ic_favorite_red_700_24dp);
                                                        ModelQuestion question = new ModelQuestion();

                                                        question.setQuestionId(questionha.get(position).getQuestionId());
                                                        question.setQuestionTitle(questionha.get(position).getQuestionTitle());
                                                        question.setQuestionDesc(questionha.get(position).getQuestionDesc());
                                                        question.setQuestionDownLink(questionha.get(position).getQuestionDownLink());
                                                        question.setQuestionDownFileName(questionha.get(position).getQuestionDownFileName());

                                                        databaseAdapter.saveQuestion(question);
                                                    } else {
                                                        Toast.makeText(v.getContext(), "از لیست علاقه مندی ها پاک شد", Toast.LENGTH_SHORT).show();
                                                        holder.imgAddFav.setImageResource(R.drawable.ic_favorite_border_red_a700_24dp);
                                                        databaseAdapter.deleteQuestion(questionha.get(position).getQuestionId());
                                                    }
                                                }
                                            }
        );
    }

    ////////////////////////////////////////////////////////////
    //================== get item count method  ================
    ////////////////////////////////////////////////////////////
    @Override
    public int getItemCount() {
        if (questionha.size() == 0) {
            return 0;
        } else {
            return questionha.size();
        }
    }
}

谢谢。

Answer 1

Loaders最适合您希望通知所有数据库更改并反射(reflect)在 UI 上的目的。

如果您正在从其他两个 Activity 对数据库进行一些更改并希望在 QuestionActivity 上更新 UI，只需制作一个加载器并在 onResume() 中启动它。

通过这个链接来实现一个加载器:
http://www.grokkingandroid.com/using-loaders-in-android/