Question

我使用 BroadcastReceiver 并注册它，这很有效，但是当按下后退按钮，我的应用显示强制关闭，在onDestroy（）我取消注册它，但我有问题这是我的代码

@SuppressLint("NewApi")
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    View v = inflater.inflate(R.layout.fragment_three, container, false);

    net = new NetworkReceiver();
    mSwipeRefreshLayout = (SwipeRefreshLayout) v.findViewById(R.id.activity_main_swipe_refresh_layout);
    list = (ListView) v.findViewById(R.id.list1);


    try {
        IntentFilter filter = new IntentFilter();
        filter.addAction(ACTION);
        //filter.addAction(ACTION2);
        getActivity().registerReceiver(net, filter);
    }
    catch (NullPointerException e){
        Log.d(TAG, "" + e);
    }}


 @Override
public void onDestroy() {

    try {
        if (net!=null) {
            getActivity().unregisterReceiver(net);
            net = null;
        }
    }
    catch (IllegalArgumentException e){
        Log.d(TAG, "ActivityVideo - onStop unregisterReceiver:" + e);
        //LocalBroadcastManager.getInstance()
    }

    super.onDestroy();
}

这是我的错误：

07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime: FATAL EXCEPTION: main
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime: Process: osclassapp.faosclass.com.osclassapp, PID: 13875
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Intent android.support.v4.app.FragmentActivity.registerReceiver(android.content.BroadcastReceiver, android.content.IntentFilter)' on a null object reference
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at osclassapp.faosclass.com.osclassapp.ThreeFragment$PostGetter$1.customLoadMoreDataFromApi(ThreeFragment.java:483)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at osclassapp.faosclass.com.osclassapp.ThreeFragment$PostGetter$1.onLoadMore(ThreeFragment.java:475)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at osclassapp.faosclass.com.osclassapp.EndlessScrollListener.onScroll(EndlessScrollListener.java:59)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at android.widget.AbsListView.invokeOnItemScrollListener(AbsListView.java:1948)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at android.widget.AbsListView.setOnScrollListener(AbsListView.java:1937)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at osclassapp.faosclass.com.osclassapp.ThreeFragment$PostGetter.onPostExecute(ThreeFragment.java:472)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at android.os.AsyncTask.finish(AsyncTask.java:636)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at android.os.AsyncTask.access$500(AsyncTask.java:177)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:653)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at android.os.Handler.dispatchMessage(Handler.java:102)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp E/AndroidRuntime:     at android.os.Looper.loop(Looper.java:145)
07-25 21:57:46.722 13875-13875/osclassapp.faosclass.com.osclassapp

这行是我的问题，请嗨我

android.content.Intentandroid.support.v4.app.FragmentActivity
.registerReceiver(android.content.BroadcastReceiver, 
android.content.IntentFilter)' 
on a null object reference

Answer 1

这是因为当你在onCreateView（）中调用它时，getActivity（）会返回null。调用片段onCreateView时，不必创建活动。

您可以将下面的代码移到onActivityCreated，您的问题就是解决。

getActivity().registerReceiver(net, filter);

Answer 2

活动尚未准备好，因此它的出现无效。如果您确保获得onActivityCreated()或onStart()等有效活动实例，请尝试注册。

BroadcastReceiver注册和取消注册不在Android中工作

2 个答案: