在完成帖子执行之前切换到另一个片段时，应用程序崩溃，并显示此错误
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【中文标题】在完成帖子执行之前切换到另一个片段时，应用程序崩溃，并显示此错误【英文标题】：when switch to another fragment before completing the post execute the app gets crashed ,and show this error 【发布时间】：2020-08-29 06:00:30 【问题描述】：类 GetDashboardContentsAysnc 扩展 AsyncTask
@Override
protected void onPreExecute()
super.onPreExecute();
shimmerFrameLayout.startShimmer();
@Override
protected void onPostExecute(String s)
super.onPostExecute(s);
shimmerFrameLayout.stopShimmer();
shimmerFrameLayout.setVisibility(View.GONE);
if(s!=null )
try
JSONObject jsonObj = new JSONObject(s);
response = jsonObj.getString("response");
if (response.contains("success"))
listcategories.clear();
JSONArray jsonArr = jsonObj.getJSONArray("catgories");
for (int i = 0; i < jsonArr.length(); i++)
JSONObject userdata = jsonArr.getJSONObject(i);
String category_id = userdata.getString("category_id");
String category_name_english = userdata.getString("category_name_english");
String app_image = url1 + userdata.getString("app_image");
HashMap<String, String> news = new HashMap<>();
news.put("category_id", category_id);
news.put("category_name_english", category_name_english);
news.put("app_image", app_image);
listcategories.add(news);
Gson gson = new Gson();
List<HashMap<String, String>> textList = new ArrayList<>();
textList.addAll(listcategories);
String jsonText = gson.toJson(textList);
session.createdbcategoryesession(jsonText);
JSONArray jsonArr1 = jsonObj.getJSONArray("slider");
for (int i = 0; i < jsonArr1.length(); i++)
JSONObject userdata = jsonArr1.getJSONObject(i);
String slider_id = userdata.getString("slider_id");
String mobile_banner = url + userdata.getString("mobile_banner");
;
String slider_url = userdata.getString("slider_url");
;
HashMap<String, String> news = new HashMap<>();
news.put("slider_id", slider_id);
news.put("mobile_banner", mobile_banner);
news.put("slider_url", slider_url);
listslider.add(news);
listrecipe.clear();
JSONArray jsonArr2 = jsonObj.getJSONArray("popular_receipe");
for (int i = 0; i < jsonArr2.length(); i++)
JSONObject userdata = jsonArr2.getJSONObject(i);
String recipe_id = userdata.getString("recipe_id");
String recipe_title = userdata.getString("recipe_title");
;
String rating = userdata.getString("rating");
String recipe_veg_status = userdata.getString("recipe_veg_status");
String image1 = url2 + userdata.getString("image1");
HashMap<String, String> news = new HashMap<>();
news.put("recipe_id", recipe_id);
news.put("recipe_title", recipe_title);
news.put("rating", rating);
news.put("recipe_veg_status", recipe_veg_status);
news.put("image1", image1);
listrecipe.add(news);
Gson gson = new Gson();
List<HashMap<String, String>> textList = new ArrayList<>();
textList.addAll(listrecipe);
String jsonText = gson.toJson(textList);
session.createdbpopularecipesesession(jsonText);
listlatestrecipe.clear();
JSONArray jsonArr4 = jsonObj.getJSONArray("latest_recipe");
for (int i = 0; i < jsonArr4.length(); i++)
JSONObject userdata = jsonArr4.getJSONObject(i);
String recipe_id = userdata.getString("recipe_id");
String recipe_title = userdata.getString("recipe_title");
;
String rating = userdata.getString("rating");
String recipe_veg_status = userdata.getString("recipe_veg_status");
String image1 = url2 + userdata.getString("image1");
HashMap<String, String> news = new HashMap<>();
news.put("recipe_id", recipe_id);
news.put("recipe_title", recipe_title);
news.put("rating", rating);
news.put("recipe_veg_status", recipe_veg_status);
news.put("image1", image1);
listlatestrecipe.add(news);
Gson gson = new Gson();
List<HashMap<String, String>> textList = new ArrayList<>();
textList.addAll(listlatestrecipe);
String jsonText = gson.toJson(textList);
session.createdblatestecipesesession(jsonText);
JSONArray jsonArr3 = jsonObj.getJSONArray("banner");
for (int i = 0; i < jsonArr3.length(); i++)
JSONObject userdata = jsonArr3.getJSONObject(i);
String section_id = userdata.getString("section_id");
String section_image = url4 + userdata.getString("section_image");
;
String sectionimage_url_website = userdata.getString("sectionimage_url_website");
;
HashMap<String, String> news = new HashMap<>();
news.put("section_id", section_id);
news.put("section_image", section_image);
news.put("sectionimage_url_website", sectionimage_url_website);
listbanner.add(news);
catch (JSONException e)
e.printStackTrace();
lay_slider.setVisibility(View.VISIBLE);
mPager.setAdapter(new ViewPagerAdaper(getActivity(),listslider));
indicator.setViewPager(mPager);
NUM_PAGES =listslider.size();
final Handler handler = new Handler();
final Runnable Update = new Runnable()
public void run()
if (currentPage == NUM_PAGES)
currentPage = 0;
mPager.setCurrentItem(currentPage++, true);
;
Timer swipeTimer = new Timer();
swipeTimer.schedule(new TimerTask()
@Override
public void run()
handler.post(Update);
, 3000, 3000);
lay_slider1.setVisibility(View.VISIBLE);
mPager1.setAdapter(new ViewPagerAdaper1(getActivity(),listbanner));
indicator1.setViewPager(mPager1);
NUM_PAGES1 =listbanner.size();
final Handler handler1 = new Handler();
final Runnable Update1 = new Runnable()
public void run()
if (currentPage1 == NUM_PAGES1)
currentPage1 = 0;
mPager1.setCurrentItem(currentPage1++, true);
;
Timer swipeTimer1 = new Timer();
swipeTimer1.schedule(new TimerTask()
@Override
public void run()
handler1.post(Update1);
, 3000, 3000);
RequestHandler requestHandler=new RequestHandler();
@Override
protected String doInBackground(String... strings)
HashMap<String, String> data = new HashMap<String, String>();
data.put("customer_id",customer_id);
data.put("type","2");
String result = requestHandler.sendPostRequest(getResources().getString(R.string.url_dashboard),data);
return result;
GetDashboardContentsAysnc getDashboardContentsAysnc=new GetDashboardContentsAysnc();
getDashboardContentsAysnc.execute();
E/androidRuntime：致命异常：AsyncTask #4 java.lang.RuntimeException：执行 doInBackground() 时发生错误 在 android.os.AsyncTask$3.done(AsyncTask.java:354) 在 java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383) 在 java.util.concurrent.FutureTask.setException(FutureTask.java:252) 在 java.util.concurrent.FutureTask.run(FutureTask.java:271) 在 android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 在 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) 在 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) 在 java.lang.Thread.run(Thread.java:764) 引起：java.lang.IllegalStateException：片段 HomeFragmentc8446f (3220b686-b1ad-479f-ba62-1f4da23bc80a) 未附加到上下文。 在 androidx.fragment.app.Fragment.requireContext(Fragment.java:774) 在 androidx.fragment.app.Fragment.getResources(Fragment.java:838) 在 .fragments.HomeFragment$1GetDashboardContentsAysnc.doInBackground(HomeFragment.java:480) 在 .fragments.HomeFragment$1GetDashboardContentsAysnc.doInBackground(HomeFragment.java:272) 在 android.os.AsyncTask$2.call(AsyncTask.java:333) 在 java.util.concurrent.FutureTask.run(FutureTask.java:266) 在 android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 在 java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167) 在 java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641) 在 java.lang.Thread.run(Thread.java:764)
【问题讨论】：
【参考方案1】：正如上面的回答中提到的，它的片段可见性问题。
String result = requestHandler
.sendPostRequest(getResources().getString(R.string.url_dashboard),data);
如果您在片段类中定义了AsyncTask，并且如果在调用getResources() 方法时没有附加片段，则会导致应用程序崩溃。在这种情况下，getResources() 方法会导致问题。
考虑进行可见性检查，
String result = "";
if(isVisible())
result = requestHandler
.sendPostRequest(getResources()
.getString(R.string.url_dashboard),data);
return result;
这应该可以解决问题，否则不要使用上下文提供的任何方法，例如 getResouces()，而是使用静态变量或直接 URL 字符串。
String result = requestHandler
.sendPostRequest("http://api_url_here",data);
希望这能解决您的问题。 问候，
【讨论】：
【参考方案2】：这是因为AsyncTask 在当前 Fragment/Activity 在后台消失时尝试更新 UI。这是必然会发生的。
为避免这种情况，您可以在Asynctask 的postExecute 方法中检查当前活动/片段是否可见。
【讨论】：
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