应用程序因NullPointerException而崩溃

Question

首先感谢您阅读我的问题。

现在我正在使用OKHTTP实现我的Android应用程序的Web服务。如果我使用快速互联网，应用程序运行速度很快。在慢速互联网上我慢慢得到数据也没关系。但问题是，如果我将一个活动切换到另一个活动而不等待响应数据调用的数据。那时它无法找到当前控件并抛出异常NullPointer。在这种情况下如何处理NullPointer错误。

它在当前活动中找到以前的活动ui控件来设置数据。

FATAL EXCEPTION: OkHttp Dispatcher
                                               Process: in.cess, PID: 16535
                                               java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.FragmentActivity.runOnUiThread(java.lang.Runnable)' on a null object reference
                                                   at in.cess.fragment.WorkRequestCompletedFragment.onResponse(WorkRequestCompletedFragment.java:221)
                                                   at com.squareup.okhttp.Call$AsyncCall.execute(Call.java:177)
                                                   at com.squareup.okhttp.internal.NamedRunnable.run(NamedRunnable.java:33)
                                                   at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
                                                   at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
                                                   at java.lang.Thread.run(Thread.java:818)

响应的活动代码。

this.getActivity().runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        mAdapter = new CallAdapter(getActivity(),movieList,
                                new CallAdapter.OnItemClickListener() {
                                    @Override
                                    public void onFeedClicked(CallDeatails jobDetails) {
                                        Intent i = new Intent(getActivity(), SalesCallDetailsActivity.class);
                                        i.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                                        i.putExtra(Const.INTENT_DATA,jobDetails);
                                        i.putExtra(Const.INTENT_TODAY,"true");
                                        getActivity().startActivity(i);

                                    }
                                });
                        RecyclerView.LayoutManager mLayoutManager = new LinearLayoutManager(getActivity().getApplicationContext());
                        recyclerView.setLayoutManager(mLayoutManager);
                        recyclerView.setItemAnimator(new DefaultItemAnimator());
                        recyclerView.setAdapter(mAdapter);

                        txt_total_call.setText("Total Call : "+String.valueOf(movieList.size()));
                    }
                });