addOnScrollListener，通过基地和限制

Question

我正在学习如何使用onscrolllistner

的RecyclerOkHttpHandler类将执行选择与基数为0，并从服务器的限制5。我要的是再次执行RecyclerOkHttpHandler来获得新的数据，examle基地5限制10.但onscrolllistner

 handler.execute().get(); 

添加下面当我得到这个错误：

Cannot execute task: the task has already been executed (a task can be executed only once) 

确定我明白我不能再执行任务，但我应该如何通过基地和限制？

这个（这是工作），将执行一类是从服务器获取的图像，但我需要通过基地0，并限制5

final RecyclerOkHttpHandler handler = new RecyclerOkHttpHandler(this, new RecyclerOkHttpHandler.MyInterface() { 
     @Override 
     public void myMethod(ArrayList result) { 
      mAdapter_first = new MyAdapter(result,SearchActivity.this); 
      mAdapter_first.notifyDataSetChanged(); 
      mRecyclerView_first.setAdapter(mAdapter_first); 
     } 
    },"girls",base,limit); 

    try { 
     handler.execute().get(); 

    } catch (Exception e) { 
     Log.d("SearchActivity error", "error in mRecyclerView_first"); 

     e.printStackTrace(); 
    } 

，这是addOnScrollListener，

mRecyclerView_first.addOnScrollListener(new RecyclerView.OnScrollListener() { 

     @Override 
     public void onScrolled(RecyclerView recyclerView, int dx, int dy) { 
      super.onScrolled(recyclerView, dx, dy); 

      visibleItemCount = mRecyclerView_first.getChildCount(); 
      totalItemCount = mLayoutManager.getItemCount(); 
      firstVisibleItem = mLayoutManager.findFirstVisibleItemPosition(); 

      if (loading) { 
       if (totalItemCount > previousTotal) { 
        loading = false; 
        previousTotal = totalItemCount; 
        System.out.println("previousTotal:" + previousTotal); 
        System.out.println("totalItemCount:" + totalItemCount); 
        System.out.println("visibleItemCount:" + visibleItemCount); 

       } 
      } 
      if (!loading && (totalItemCount - visibleItemCount) 
        <= (firstVisibleItem + visibleThreshold)) { 
       // End has been reached 
       System.out.println(totalItemCount); 

       Log.i("Yaeye!", "end called"); 
     //  base =String.valueOf(firstVisibleItem); 
     //   limit=String.valueOf(visibleItemCount); 

       // Do something 
       try { 
        handler.execute().get(); 

       } catch (Exception e) { 
        Log.d("SearchActivity error", "error in mRecyclerView_first"); 

        e.printStackTrace(); 
       } 
       loading = true; 
      } 
     } 
    }); 

这是类RecyclerOkHttpHandler

public class RecyclerOkHttpHandler extends AsyncTask<String, Void, String> { 
    private Context mContext; 
    private MyInterface mListener; 
    public String category; 
    public String basestart; 
    public String limitend; 
    public RecyclerOkHttpHandler(Context context, MyInterface mListener, String categ, String base, String limit){ 
     mContext = context; 
     this.mListener = mListener; 
     category=categ; 
     basestart=base; 
     limitend=limit; 
    } 
    public interface MyInterface { 
     public void myMethod(ArrayList result); 
    } 

    private final String Fetch_URL = "http://justedhak.com/old-files/Recyclerview_data.php"; 
    // ArrayList<Listitem> Listitem; 
    ArrayList<CategoryList> Listitem; 
    int resulta; 

    OkHttpClient httpClient = new OkHttpClient(); 
    ListView list; 
    String myJSON; 
    JSONArray peoples = null; 
    InputStream inputStream = null; 

    @Override 
    protected String doInBackground(String... params) { 
     Log.d("okhttp Fetch_URL", Fetch_URL); 



     RequestBody formBody = new FormEncodingBuilder() 
       .add("category", category) 
       .add("base", basestart) 
       .add("limit", limitend) 
       .build(); 
     Request request = new Request.Builder() 
       .url(Fetch_URL) 
       .post(formBody) 
       .build(); 


     String result = null; 
     try { 
      Response response = httpClient.newCall(request).execute(); 
      if (!response.isSuccessful()) throw new IOException("Unexpected code " + response); 
      inputStream = response.body().byteStream(); 
      BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8); 
      StringBuilder sb = new StringBuilder(); 
      String line = null; 
      while ((line = reader.readLine()) != null) 
      { 
       sb.append(line + "\n"); 
      } 
      result = sb.toString(); 
      resulta = 1; //"Success 
      // return response.body().bytes(); 
     } catch (Exception e) { 
      Toast.makeText(mContext, "Connection failed, check your connection", 
        Toast.LENGTH_LONG).show(); 
      e.printStackTrace();  } 
     finally { 
      try{if(inputStream != null)inputStream.close();}catch(Exception squish){} 
     } 
     return result; 
    } 
    @Override 
    protected void onPostExecute(String result){ 
     if(resulta ==1){ 
      myJSON=result; 
      Log.e("result",result); 

      showList(); 
     } 
     else{ 
      Log.e("d","there is an error on postexecute in okhhttphandler.java"); 

     } 
    } 

    protected void showList(){ 
     try { 

      JSONObject jsonObj = new JSONObject(myJSON); 
      peoples = jsonObj.getJSONArray("result"); 
      System.out.println("Length:"+peoples.length()); 
      int J_length=peoples.length()-1; 
      //JSONObject maxj = peoples.getJSONObject(peoples.length() - 1); 
      // max of arrray 

      jsonObj= peoples.getJSONObject(J_length); 

      String j_id= jsonObj.getString("id"); 
      int _id = Integer.parseInt(j_id); 
      System.out.println(j_id); 

      //max of 
      DatabaseHandler db = new DatabaseHandler(mContext); 
      String db_id=""; 
      db_id = db.getmax(); 
      if (db_id== null) 
      { 
       db_id="0"; 
      } 
      int d_id = Integer.parseInt(db_id); 
      Log.e("db_id", db_id); 
      Log.e("j_id",j_id); 

      // if (_id < d_id) { 
      System.out.println("Getting json result "); 

      Listitem = new ArrayList<CategoryList>(); 
      for (int i = 0; i < peoples.length(); i++) { 
       JSONObject c = peoples.getJSONObject(i); 

       String id = c.getString("id"); 
       String url = c.getString("url"); 



       Listitem.add(new CategoryList(id, url)); 
      } 

      if (mListener != null) 
       mListener.myMethod(Listitem); 


     } catch (JSONException e) { 
      e.printStackTrace(); 
     } 
    } 





} 

Answer 1

我再次看了你的问题，和S解决方案可能只是每次创建一个新的RecyclerOkHttpHandler。这就是错误信息所说的，这就是AsyncTasks的工作原理。如果您在调用.execute（）后无法再次调用它，则必须创建一个新对象。

还是应该重写onPostExecute（）否则你会阻塞UI线程。看看AsyncTask。 我需要RecyclerOkHttpHandler的代码来说更多...