即使使用cancel方法也无法取消AsyncTask中的doInBackground进程

我已经声明了FileUploadTask的实例，它在onCreate（）方法中扩展了AsyncTask

FileUploadTask uploadTask= null; 

并通过以下代码执行后台方法

  public class UploadFiles implements OnClickListener{ .... if(SOTCNetStat.chkConnectionStatus(UploadResult.this)){ uploadTask=new FileUploadTask(); uploadTask.execute(""); } else { Toast.makeText(UploadResult.this, getResources().getString(R.string.Text_CheckNetworkConnections) , Toast.LENGTH_LONG).show(); } .... } 

有取消按钮取消后台进程

  cancel.setOnClickListener(new OnClickListener() { @Override public void onClick(View v) { // TODO Auto-generated method stub Log.d(TAG,"cancel button clicked....."); //FileUploadTask uploadTask= new FileUploadTask(); if(uploadTask!=null) { Log.d(TAG,"click event null checking...."); uploadTask.cancel(true); } } } 

在FileUploadTask类中声明了一个布尔值来检查运行状态

  public class FileUploadTask extends AsyncTask { .... boolean isRunning=true; 

doInBackground方法

  @Override protected String doInBackground(String... arg0) { for(int i=0; i<fp.size(); i++){ index = i+1; if(isCancelled() && !isRunning) { Log.d(TAG,"Cancel 1 Condition Checked ["+i+"]"); Log.d(TAG,"doInBackground canceled"); break; } else { Log.d(TAG,"Cancel 1 Canceled ["+i+"]"); } file1 = new File(fp.get(i)); String urlString = Constants.UPLOAD_URL; try { Log.e("doInBackground", "urlString: " + urlString); Log.e("doInBackground", "domainPref: " + domainName); urlString = urlString.replace("domain", URLEncoder.encode(domainName, "UTF-8")); } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } try { HttpClient client = new DefaultHttpClient(); HttpPost post = new HttpPost(urlString); FileBody bin1 = new FileBody(file1); ProgressMultipart reqEntity = new ProgressMultipart(new ProgressListener() { @Override public void transferred(long num) { //publishProgress((int) ((num / (float) file1.length() ) * 100)); publishProgress((int) ((num / (float) totalSize ) * 100)); } }); reqEntity.addPart("userfile", bin1); if(getIntent().hasExtra("show_id")) { //String showId = getIntent().getStringExtra("show_id"); reqEntity.addPart("mobileshow", new StringBody("1")); reqEntity.addPart("show_ids", new StringBody(getIntent().getStringExtra("show_id"))); } reqEntity.addPart("Filename", new StringBody(file1.getName())); reqEntity.addPart("user_id", new StringBody("2")); reqEntity.addPart("privateasset", new StringBody("true")); reqEntity.addPart("uploadtype", new StringBody("Normal")); reqEntity.addPart("version_num", new StringBody("1")); totalSize = reqEntity.getContentLength(); post.setEntity(reqEntity); System.err.println("post :"+post.toString()); //to be check the cancel operation if(isCancelled() && !isRunning) { Log.d(TAG,"Cancel 2 Condition Checked ["+i+"]"); Log.d(TAG,"File Uploading Cancelled in doInBackground method"); break; } else { Log.d(TAG,"Cancel 2 Canceled ["+i+"]"); } HttpResponse response = client.execute(post); resEntity = response.getEntity(); response_str = EntityUtils.toString(resEntity); } .... return response_str; } 

并重载onCancelled方法

 @Override protected void onCancelled() { // TODO Auto-generated method stub Log.d(TAG,"onCancelled() method called"); super.onCancelled(); } @Override protected void onCancelled(String result) { // TODO Auto-generated method stub Log.d(TAG,"onCancelled(String) method called"); isRunning=false; this.cancel(true); } 

我尝试了很多并且进行了探索。 即使使用取消方法，我也无法在后台停止上传过程。 请任何人给出问题的解决方案我提到的一些链接

Android – Cancel AsyncTask in Android

http://developer.android.com/reference/android/os/AsyncTask.html

Answer 1

您似乎错过了AsyncTask工作原理。 只有在doInBackground()完成后doInBackground()调用onPostExecute()方法，类似于onPostExecute()方法。 在调用uploadTask.cancel(true)之后不会立即调用它。 您使用它的方式，您不需要onCancelled()方法或isRunning变量（当前在您的代码中， isRunning永远不会更改为false ，因此您的isCancelled()检查永远不会起作用）。 删除onCancelled()方法和isRunning变量， AsyncTask将起作用。

Answer 2

检查这个，取消asynctask后写这个条件。

 if(asynctask.iscancel()){ break; } 

它可能对你有所帮助。 🙂

http://developer.android.com/reference/android/os/AsyncTask.html