Question

Update 2

Logcat:

03-02 19:03:47.616: E/AndroidRuntime(881): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{TheTask}: java.lang.InstantiationException:  .TheTask
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569)
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663)
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.app.ActivityThread.access$1500(ActivityThread.java:117)
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931)
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.os.Handler.dispatchMessage(Handler.java:99)
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.os.Looper.loop(Looper.java:123)
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.app.ActivityThread.main(ActivityThread.java:3683)
03-02 19:03:47.616: E/AndroidRuntime(881):  at java.lang.reflect.Method.invokeNative(Native Method)
03-02 19:03:47.616: E/AndroidRuntime(881):  at java.lang.reflect.Method.invoke(Method.java:507)
03-02 19:03:47.616: E/AndroidRuntime(881):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-02 19:03:47.616: E/AndroidRuntime(881):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-02 19:03:47.616: E/AndroidRuntime(881):  at dalvik.system.NativeStart.main(Native Method)
03-02 19:03:47.616: E/AndroidRuntime(881): Caused by: java.lang.InstantiationException: TheTask
03-02 19:03:47.616: E/AndroidRuntime(881):  at java.lang.Class.newInstanceImpl(Native Method)
03-02 19:03:47.616: E/AndroidRuntime(881):  at java.lang.Class.newInstance(Class.java:1409)
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.app.Instrumentation.newActivity(Instrumentation.java:1021)
03-02 19:03:47.616: E/AndroidRuntime(881):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561)

layout

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="horizontal" >

    <ProgressBar
        android:id="@+id/the_progress"
        style="?android:attr/progressBarStyleLarge"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />
 <ListView
     android:id="@+id/android:list"
     android:layout_width="fill_parent"
     android:layout_height="wrap_content"
     android:layout_weight="0.63" />
</LinearLayout>

TestingAsyncTask

//The class that starts the task
public class TestingAsyncTask extends ListActivity {

    private ProgressBar bar = null; 
    private ArrayList<String> data = new ArrayList<String>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.thetask);
        bar = (ProgressBar) findViewById(R.id.the_progress);
        data.add("1");
        data.add("2");
        data.add("3");

        Log.d("create", ""+ data.size());

        setListAdapter(new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, data));
        new TheTask(this).execute((Void) null);     
    }

    public ArrayList<String> getData() {
        return data;
    } 
}

thetask.java async file

//The AsyncTask class
public class TheTask extends AsyncTask<Void, Void, List<String>> {

    Context c;

    public TheTask(Context c) {
        this.c = c;
    }   

    @Override
    protected void onPreExecute() {
        ((TestingAsyncTask) c).findViewById(R.id.the_progress).setVisibility(View.VISIBLE);
    }



    @Override
    protected List<String> doInBackground(Void... params) {
        try {
            Thread.sleep(5000);
        } catch (InterruptedException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        ArrayList<String> res= new ArrayList<String>();
        res.add("a");
        res.add("b");
        res.add("c");
        Log.d("doinbacground", ""+ res.size());
        return res;
    }

    @Override
    protected void onPostExecute(List<String> result) {
        TestingAsyncTask activity = ((TestingAsyncTask) c);
        activity.getData().clear();
        activity.getData().addAll(result);
        ((ArrayAdapter)activity.getListAdapter()).notifyDataSetChanged();
        ((TestingAsyncTask) c).findViewById(R.id.the_progress).setVisibility(View.GONE);
    }

}

End Update 2

Update1:

Description Resource    Path    Location    Type
m_ProgressDialog cannot be resolved GrabUrlAsyncTask.java   
line 81 Java Problem
The field Main.m_orders is not visible   GrabUrlAsyncTask.javaline 79   
Java Problem
The field Main.m_ProgressDialogis not visible   GrabUrlAsyncTask.javaline 
80  Java Problem
The method notifyDataSetChanged() is undefined for the type ListAdapter GrabUrlAsyncTask.java   
line 82 Java Problem

Update:

@Override 
        protected void onPostExecute(List<Employee> result) 
        {            
            //showToast("You have to be connected to the internet for this application to work");   
            m_orders.clear();     
            m_orders.addAll(result);   
            progress.dismiss();
            mContext.m_adapter.notifyDataSetChanged();   
        } 

I’ve been working on an app and I’ve managed to get the AsyncTask to work fine when it’s an inner class, which means in the same main.java class and when i looked at the code and it look so hard to get into and i am planning of doing refactoring the code so that the AsyncTask will have its onw separate class.

i started to doing it but then it raised few questions like, how would i show the ProgressDialog box or toastText

can anbydoy give me some direction please?

here is my code:

public class Main extends ListActivity{

     @Override
     public void onCreate(Bundle savedInstanceState) 
     {
           ............
           .............
           new taskDoSomething().execute();


     } //

     private class taskDoSomething extends AsyncTask<Void, Void, List<Employee>> 
     {
           @Override 
      protected List<Surah> doInBackground(Void... params) 
      {
                //do some stuffs...
                try {
                     ///
                catch (Exception e)
                {
                   //
                }

            } 

            protected void onProgressUpdate(Void... values)
      {
              super.onProgressUpdate(values);         
         m_ProgressDialog.dismiss();  
            } 

            protected void onPostExecute(List<Employee> result)
      {
              m_orders.clear();     
        m_orders.addAll(result);   
        m_ProgressDialog.dismiss();
        m_adapter.notifyDataSetChanged();             
           }  
     } 
}

Answer 1

Create a constructor in your AsyncTask that takes a Context like this:

private Context context; //field in your AsyncTask

public taskDoSomething(Context context) {
    this.context = context;
}

and then in your activity where you create the task:

new taskDoSomething(this).execute();

Now in your AsyncTask you have a Context(that you can cast back to your activity) and you can use this context to show the things you want.

EDIT:
Cast the Context parameter to your class and then you can access all the fields for that class. For example if your m_orders is a public field in your class you can access it like bellow or you can make a getter/setter method for the m_orders :

protected void onPostExecute(List<Employee> result) {
         Main activity = (Main) context;
         activity.m_orders.clear();     
         activity.m_orders.addAll(result);   
         m_ProgressDialog.dismiss();
         activity.getListAdapter().notifyDataSetChanged();             
}