应用程序关闭后如何在片段中停止AsyncTask

Question

如何在关闭应用程序后停止片段类中的AsyncTask.

这是我的情况:

MainActivity类

public class MainActivity extends FragmentActivity {

}

BaseFragment类由Fragment扩展

public class BaseFragment extends Fragment {
    public MainActivity mActivity;


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        mActivity       =   (ChatActivity)this.getActivity();

    }

    public boolean onBackPressed(){
        return false;
    }

    public void onActivityResult(int requestCode, int resultCode, Intent data){

    }

    @Override
    public void onDestroy() {
        // TODO Auto-generated method stub
        super.onDestroy();
    }


}

片段类

public class Fragment1 extends BaseFragment{


private  Update  task;
@Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {

        toCallAsynchronous();

        return inflater.inflate(R.layout.activity_online_korisnici, container,
                false);
    }


     public void toCallAsynchronous() {
            final Handler handler = new Handler();
            Timer timer = new Timer();
            TimerTask doAsynchronousTask = new TimerTask() {       
                @Override
                public void run() {
                    handler.post(new Runnable() {
                        public void run() {       
                            try {
                             task =new Update();

                                // PerformBackgroundTask this class is the class that extends AsynchTask 
                                task.execute("");
                            } catch (Exception e) {
                                // TODO Auto-generated catch block
                            }
                        }
                    });
                }
            };
            timer.schedule(doAsynchronousTask, 0, 5000); //execute in every 50000 ms
        }




   private class Update extends AsyncTask<Object, Object, List<Object>>{

    @Override
        protected List<Object> doInBackground(Object... params) {

                 }

@Override
        protected void onPostExecute(List<Object> result) {


}

   }


}

我认为这可以在 MainActivity - > onPause()方法中完成,但是如何.

Answer 1

您可以使用Fragment的onPause()方法.当片段不再恢复时调用它.这通常与Activity.onPause包含Activity的生命周期有关.

@Override
public void onPause() {
    super.onPause();
    task.cancel();
}

更新:如果您在TabHost下,并且在按下不同的选项卡时暂停片段,则可以执行此操作

在您的活动中存储片段ID或标签

实现一种方法来停止片段中的任务

public void onActivityPause() {
    task.cancel();
}

在你的活动onPause()

@Override
protected void onPause() {
    super.onPause();
    FragmentManager fm = getFragmentManager();
    for (int id : ids) {
        Fragment f = fm.findFragmentById(id);
        try {
            Method stop = f.getClass().getMethod("onActivityPause");
            close.invoke(f);
        } catch (Exception e) {}
    }
}

但无论如何我不会使用TabHost,它已被弃用.如果需要支持v4版本,请考虑使用ActionBar或ActionBarSherlock.