Finish the calling activity when AsyncTask completes

问题

My calling activity:

public class Hello extends Activity {  

public void onCreate(Bundle savedInstanceState) {

    MyTask mt = new MyTask(this);
    mt.execute();
}

Now In MyTask (an external class):

public class MyTask extends AsyncTask<Void, Void, Void> {
private Context mContext;

public MyTask(Context context) {

    mContext = context;
}  

//doinbackground, etc

    protected void onPostExecute() {
    mContext.finish();

}

Other things are working as expected if I remove mContext.finish() above.
But if I'm calling mContext.finish() , I'm getting an error: The method finish() is undefined for the type Context (Eclipse doesn't show finish() when I write mContext. so that suggests I'm using finish() wrongly.)

What do I need to do to finish the calling activity Hello after MyTask completes the task

回答1:

((Activity)mContext).finish();

Would be the correct way to cast a Context to an Activity and call its finish() method. Not sure why you'd want to finish an Activity from an AsyncTask though

回答2:

What you can try to do instead of calling context.finish(), why don't you do a callback interface like this:

public interface TaskCallback{
void done();
}

Then you implement this into your Activity

public Hello extends Activity implements TaskCallback{

    .....BUNCH OF ACTIVITY CODE.....

public void onCreate(Bundle savedInstanceState) {

    MyTask mt = new MyTask(this);
    mt.execute();
}

public void done() {
     finish();
}

}

And instead of having Context as a parameter you have TaskCallback

public class MyTask extends AsyncTask<Void, Void, Void> {
private TaskCallback mCallback;

public MyTask(TaskCallback callback) {

    mCallback = callback;
}  

//doinbackground, etc

    protected void onPostExecute() {
    mCallback.done();

}

There you go, it gives you more flexibility to custom each implementation.

回答3:

I got the same situation, then I do as follows:

public class MyTask extends AsyncTask<Void, Void, Void> {
private Activity mActivity;
private Context mContext;

public MyTask(Activity activity) {
    mActivity = activity;
    mContext = mActivity.getApplicationContext();
}  

//doinbackground, etc

protected void onPostExecute() {
    mActivity.finish();

}

Hope it help :)

回答4:

Define a method in your activity class like this:

public void FinishAfterAsyncTask()
{
   this.finish();
}

And call this method from the OnPostExecute method of the AsynTask class.

回答5:

You could create a new private AsyncTask extended from your public one.

In this private AsyncTask you have access to the Activity stuff and you can override the onPostExecute method to finish it.

Your truly AsyncTask

public class MyPublicAsyncTask extends AsyncTask<Void, Void, Void> {
    Context context;
    public GetHorariosAsyncTask(Context ctx){
        context = ctx;
    }
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        // prepare yourself for an async work
    }
    @Override
    protected Void doInBackground(Void... params) {
        // Do yout cool async stuff
    }
    @Override
    protected void onPostExecute(Void result) {
        super.onPostExecute(result);
       // you're finish, let's tell to user
    }
}

Your Activity with private AsyncTask

public class MyActivity  extends Activity {
    Activity mAct;

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        mAct = this;
    }

    private class MyPrivateAsyncTask extends MyPublicAsyncTask {

        public MyPrivateAsyncTask(Context ctx) {
            super(ctx);
            // TODO Auto-generated constructor stub
        }

        @Override
        protected void onPostExecute(Void result) {
            // TODO Auto-generated method stub
            super.onPostExecute(result);
            // our async task is completed! let's take care of this activity
            mAct.finish();
        }

    }
}