Boolean Value Does Not Change On Clicking Cancel Button - How To Stop Asynctask - Android?

I am a beginner, so please explain your answer clearly. Thanks EDIT 2 I now have public class MainActivity extends Activity { //other declarations public ReadTask

Solution 1:

Hi i made some changes in your code with explanation please check.

publicclassAsynextendsActivity {

    publicReadTask readTask;
    // keep global to prevent creating new async task on every time button clickboolean isCancelled = true;
    TextView results1;
    Button start, end;

    protectedvoidonCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.qww);
        start = (Button) findViewById(R.id.button1);
        end = (Button) findViewById(R.id.button2);
        start.setOnClickListener(test);
        end.setOnClickListener(cancel);
        results1 = (TextView) findViewById(R.id.textView1);
    }

    privateOnClickListener test = newOnClickListener() {
        @OverridepublicvoidonClick(View V) {
            if (isCancelled) { // checked to prevent creating new async task on// every time button clickToast.makeText(Asyn.this, "new task started", Toast.LENGTH_LONG)
                        .show();
                readTask = newReadTask();
                readTask.execute();
                isCancelled = false;
            } else {
                Toast.makeText(Asyn.this, "Task already runing",
                        Toast.LENGTH_LONG).show();
            }

        }

    };
    privateOnClickListener cancel = newOnClickListener() {
        @OverridepublicvoidonClick(View V) {
            if (null != readTask) {
                Toast.makeText(Asyn.this, "Task stop", Toast.LENGTH_LONG)
                        .show();
                readTask.cancel(true);
                isCancelled = true;
            }
            results1.setText("");
        }
    };

        privateclassReadTaskextendsAsyncTask<Void, String, Void> {


    protectedvoidonProgressUpdate(String... values) {
         super.onProgressUpdate(values);
        results1.setText(values[0].toString());


    }
    @OverrideprotectedVoiddoInBackground(Void... params) {

        try {
            for (int k = 0; k <= 10; k++) {
                // bunch of codeLog.w("5.newString", k + "");
                String isC1 = String.valueOf(isCancelled);
                Log.w("5.Is cancelled?", isC1); // at this point, VALUE IS//below line for instant update as soon as the value is changedpublishProgress("  "+k + "");

                // use thread to see the update otherwise remove itThread.sleep(2000); 
                if (isCancelled() || isCancelled == true) {
                    Log.d("Entered", "WHY");
                    break;
                }

                // bunch of code

            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        returnnull;

    }

    @OverrideprotectedvoidonPostExecute(Void result) {
        // TODO Auto-generated method stubsuper.onPostExecute(result);
        // assign true to isCancelled so that user can start task again
        isCancelled = true;
    }
}
}

Solution 2:

It's not working because each time you are creating new object from ReadTask. if you want to cancel existing job. you should do this :

publicclassMainActivityextendsActivity { 
   ReadTask readTask; 

   @OverridepublicvoidonCreate(Bundle b) {
       ...
       readTask = newReadTask();

       btnStart.setOnClickListener(newOnClickListener() {
          @OverridevoidonClick(View v) {
            readTask.execute();
          }
       }

       btnCancel.setOnClickListener(newOnClickListener() {
          @OverridevoidonClick(View v) {
            readTask.cancel();
          }
       }
   }

 }

Solution 3:

new ReadTask().onCancelled();
new ReadTask().cancel(true);

this part of your code is wrong for both of them refers to different instance of ReadTask class. you can declare a global variable of ReadTask class

public ReadTask rt;

and initialize it on your onCreate() method.

rt = new ReadTask();

then you can already use it on every part of your activity start it using rt.execute() and stop it using rt.cancel(true)