异步任务中的 doinbackground() 无法正常工作

Posted 2023-02-22

【中文标题】异步任务中的 doinbackground() 无法正常工作

【英文标题】：doinbackground() in async task not working properly

【发布时间】：2019-03-22 05:14:10

【问题描述】：

我正在从 API 获取一些数据并将每个项目显示为 RecyclerViewPager slide。所以，我在onScrollListener 中创建了一个async task 来检查滚动动作，当用户滑动5 个项目时asynctask 获取第2 页的项目，在doInBackGround 函数中，数据将被添加到数组和数组中将被添加到recycler view pager。

一切正常，但我需要在 5 幻灯片停止滚动几秒钟（至少 5 秒），否则 recyclerView 将不会显示第二页幻灯片。

如何解决这个问题。这是我用于onScrollListener 和asyncTask 函数的代码。

代码：

 private void initRecycler()

       final RecyclerViewPager mRecyclerView = (RecyclerViewPager) findViewById(R.id.list);

// setLayoutManager like normal RecyclerView, you do not need to change any thing.
       final LinearLayoutManager layout = new LinearLayoutManager(this,LinearLayoutManager.HORIZONTAL,false);
       mRecyclerView.setLayoutManager(layout);

//set adapter
//You just need to implement ViewPageAdapter by yourself like a normal RecyclerView.Adpater.
       RecyclerViewAdapter adapter = new RecyclerViewAdapter(ImageUrls, ImageNames, ImageDesc, this);
       mRecyclerView.setAdapter(adapter);

       mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() 

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

              visibleItemCount = layout.getChildCount();
              totalItemCount = layout.getItemCount();
               firstVisibleItem = layout.findFirstVisibleItemPosition();
//               int aaa = totalItemCount - visibleItemCount;
//               int bbb = firstVisibleItem + visibleThreshold;
//               Log.d("tag" ,"totalItemCount : " + totalItemCount + "|  visibleItemCount : " + visibleItemCount);
              Log.d("tag" ,"totalItemCount : " + totalItemCount + "|  previousTotal : " + previousTotal);
               Log.d("tag", "firstVisibleItem :" + firstVisibleItem + " | totalItemCount :" + totalItemCount);
               if (loading) 
                   if (totalItemCount > previousTotal) 
                       loading = false;
                       previousTotal = totalItemCount;
                   
               
               if (!loading && (firstVisibleItem + 5)
                       == (totalItemCount)) 

                   Log.i("Ya!", "end called");
                   page += 1;
                   String url = "http://url.in/wp-json/wp/v2/posts?page="+page+"&_embed";
                   Log.d( url ,": ");
                   // Do something
                   final OkHttpClient client2 = new OkHttpClient();
                   final Request request2 = new Request.Builder()
                           .url(url)
                           .build();
                   @SuppressLint("StaticFieldLeak") AsyncTask<Void, Void, String> asyncTask = new AsyncTask<Void, Void, String>() 
                       private static final String TAG = "SlideFragment";

                       @Override
                       protected String doInBackground(Void... params) 

                           try 

                               Response response2 = client2.newCall(request2).execute();

                               if (!response2.isSuccessful()) 
                                   Log.d(TAG, "doInBackground: REsponse Un Successfull - 56");
                                   response2.body().close();
                                   return null;

                               
                               String Data2 =  response2.body().string();
                               response2.body().close();
                               return Data2;
                            catch (Exception e) 
                               e.printStackTrace();
                               Log.d(TAG, "doInBackground: Exceptione on line63");
                               return null;
                           

                       

                       @Override
                       protected void onPostExecute(String Data2) 

                           super.onPostExecute(Data2);
                           if (Data2 != null) 
                               Log.d(TAG, "onPostExecute: 188 LINE");
                               try 
                                   JSONArray json = new JSONArray(Data2);
                                   for (int i = 0; i < json.length(); i++) 
                                       JSONObject post = json.getJSONObject(i);
                                       String title = post.getJSONObject("title").getString("rendered");
                                       String description = post.getJSONObject("excerpt").getString("rendered");
                                       String imgURL = post.getJSONObject("_embedded").getJSONArray("wp:featuredmedia").getJSONObject(0).getJSONObject("media_details").getString("file");
                                       String imagUrl = "http://url.in/wp-content/uploads/" + imgURL;
                                       ImageNames.add(title);
                                       ImageDesc.add(description);
                                       ImageUrls.add(imagUrl);
                                       Log.d(TAG, "onPostExecute: arrayList Created" );
                                   


                               catch(JSONException j)
                                   j.printStackTrace();
                                   Log.d(TAG, "onPostExecute: on line 121");
                               
                           
                       
                   ;
                   asyncTask.execute();
                   loading = true;
               
           
       );

   

【参考方案1】：

我猜你应该在发出另一个请求之前手动取消任务，因为根据文档中给出的规则，一个任务只能执行一次