我們如何使用Android下載管理器和RecyclerView？

Question

我有一個QuestionActivity那裏我有一個多個問題。在RecyclerView的每個項目中。我有一個按鈕，我希望下載管理器在單擊此按鈕時開始下載。

這是我的AdapterRecyclerQuestion：

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


    private Context context; 
    private ArrayList<ModelQuestion> questionha; 

    //constructor 

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

    //viewholder 
    public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener { 
     private TextView txtTitle; 
     private TextView txtDesc; 
     private TextView txtCntDown; 
     private ImageView imgAuthorPic; 
     private TextView txtAuthorName; 
     private TextView txtDate; 
     private Button btnDownload; 

     public ViewHolder(View itemView) { 
      super(itemView); 
      itemView.setOnClickListener(this); 
      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); 
      imgAuthorPic = (ImageView) itemView.findViewById(R.id.img_author_pic_question); 
      txtAuthorName = (TextView) itemView.findViewById(R.id.txt_author_name_question); 
      txtDate = (TextView) itemView.findViewById(R.id.txt_date_question); 
      btnDownload = (Button) itemView.findViewById(R.id.btn_down_question); 

     } 

     @Override 
     public void onClick(View v) { 
      Toast.makeText(v.getContext(), "Hello" + txtTitle.getText(), Toast.LENGTH_SHORT).show(); 
     } 
    } 
    //oncreateviewholder 

    @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); 
    } 

    //onbindviewholder 

    @Override 
    public void onBindViewHolder(final ViewHolder holder, final int position) { 
     holder.txtTitle.setText(questionha.get(position).getQuestionTitle()); 
     holder.txtDesc.setText(questionha.get(position).getQuestionDesc()); 
     holder.txtCntDown.setText(questionha.get(position).getQuestionDownCnt()); 
     holder.txtAuthorName.setText(questionha.get(position).getQuestionAuthorName()); 
     Glide.with(holder.itemView.getContext()).load(questionha.get(position).getQuestionAuthorPic()).into(holder.imgAuthorPic); 
     holder.txtDate.setText(questionha.get(position).getQuestionDate()); 
     holder.btnDownload.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
====>    DownloadManager downloadManager = context.getSystemService(context.DOWNLOAD_SERVICE); 
       DownloadManager.Request request = new DownloadManager.Request(Uri.parse(questionha.get(position).getQuestionDownLink())); 
       request.setTitle(questionha.get(position).getQuestionTitle()) 
         .setDescription("Downloading") 
         .setDestinationInExternalFilesDir(context, "Questions",questionha.get(position).getQuestionTitle()); 

      } 
     }); 

    } 

    //getitemcount 
    @Override 
    public int getItemCount() { 
     return questionha.size(); 
    } 
} 

現在，當我在我的onBindViewHolder代碼添加到按鈕onClick它說，我需要不Java.lang.Object。

Answer 1

context.getSystemService將返回Object。這取決於程序員將其轉換爲所需的類。因此，改變你的線路：

DownloadManager downloadManager = (DownloadManager) context.getSystemService(context.DOWNLOAD_SERVICE); 

這將是DownloadManager型的並不僅僅是Object。