Question

我有一个ViewPager在视图分页器中有3个列表，每个列表都有一个简单的SwipeRefreshLayout它运行良好但是当RefreshLayout重新填充并按下后退按钮（onPause我认为？）程序将崩溃，错误是你不能设置null对象我知道问题我不知道如何解决它请帮助这是我的代码

    public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
   View view= inflater.inflate(R.layout.activity_fragment1,container,false);

    mListView = (ListView) view.findViewById(R.id.list_news);
    refresh = (SwipeRefreshLayout) view.findViewById(R.id.refresh);
    refresh.setColorSchemeColors(
            R.color.material_green_200,
            R.color.material_green_400,
            R.color.material_green_600,
            R.color.material_green_800
    );
    refresh.setOnRefreshListener(new SwipeRefreshLayout.OnRefreshListener() {
        @Override
        public void onRefresh() {
            String uri = "http://192.168.1.101/mySite/Flowers/flowers.json";
            JsonArrayRequest request = new JsonArrayRequest(uri,
                    new Response.Listener<JSONArray>() {
                        @Override
                        public void onResponse(JSONArray response) {
                            JsonParser parser = new JsonParser();
                            ArrayList items = parser.parseJson(response);
                            FlowerAdapter adapter = new FlowerAdapter(getContext(),
                                    R.layout.activity_last_news_fragment,items);
                            mListView.setAdapter(adapter);

                        }
                    },
                    new Response.ErrorListener() {
                        @Override
                        public void onErrorResponse(VolleyError error) {
                            Toast.makeText(getContext(), "error", Toast.LENGTH_SHORT).show();
                        }
                    });
            RequestQueue quew = Volley.newRequestQueue(getActivity().getApplicationContext());
            quew.add(request);
            refresh.setRefreshing(false);
        }
    });

   String uri = "http://192.168.1.101/mySite/Flowers/flowers.json";
    JsonArrayRequest request = new JsonArrayRequest(uri,
            new Response.Listener<JSONArray>() {
                @Override
                public void onResponse(JSONArray response) {
                    JsonParser parser = new JsonParser();
                    ArrayList items = parser.parseJson(response);
                    FlowerAdapter adapter = new FlowerAdapter(getContext(),
                            R.layout.activity_last_news_fragment,items);
                    mListView.setAdapter(adapter);

                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    Toast.makeText(getContext(), "error", Toast.LENGTH_SHORT).show();
                }
            });

    RequestQueue quew = Volley.newRequestQueue(getActivity().getApplicationContext());
    quew.add(request);
    return view;

}

@Override
public void onPause() {
    if (refresh.isRefreshing()){
        refresh.setEnabled(false);
    }else {
        super.onPause();
    }

}

如何覆盖onpause方法，以便在第一次停止刷新然后暂停时停止？

这是竞争错误日志

12-07 17:11:41.942 13992-13992/app.mma.introsliderproject E/AndroidRuntime: FATAL EXCEPTION: main
                                                                        Process: app.mma.introsliderproject, PID: 13992
                                                                        java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.Context android.support.v4.app.FragmentActivity.getApplicationContext()' on a null object reference
                                                                            at app.mma.PokerInfo.twitch.TwitchFragment$2.onResponse(TwitchFragment.java:73)
                                                                            at app.mma.PokerInfo.twitch.TwitchFragment$2.onResponse(TwitchFragment.java:67)
                                                                            at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:65)
                                                                            at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99)
                                                                            at android.os.Handler.handleCallback(Handler.java:739)
                                                                            at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                            at android.os.Looper.loop(Looper.java:148)
                                                                            at android.app.ActivityThread.main(ActivityThread.java:7409)
                                                                            at java.lang.reflect.Method.invoke(Native Method)
                                                                            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230)
                                                                            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120)

Answer 1

这导致Volley.newRequestQueue(getActivity().getApplicationContext());内的问题onRefresh()。您需要检查您的活动是否处于运行状态，即上下文是否为空。

@Override
    public void onRefresh () {
        if (YourFragment.this.isVisible()) {
            String uri = "http://192.168.1.101/mySite/Flowers/flowers.json";
            JsonArrayRequest request = new JsonArrayRequest(uri,
                new Response.Listener<JSONArray>() {
                    @Override
                    public void onResponse(JSONArray response) {
                        JsonParser parser = new JsonParser();
                        ArrayList items = parser.parseJson(response);
                        FlowerAdapter adapter = new FlowerAdapter(getContext(),
                                R.layout.activity_last_news_fragment,items);
                        mListView.setAdapter(adapter);

                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Toast.makeText(getContext(), "error", Toast.LENGTH_SHORT).show();
                    }
                });
        RequestQueue quew = Volley.newRequestQueue(getActivity().getApplicationContext());
        quew.add(request);
        refresh.setRefreshing(false);
        }
    }

将所有内容放在if(){}内以避免崩溃

的onPause（）;对于SwipeRefreshLayout不起作用

1 个答案: