Question

我正在开发一个使用eclipse和retrofit的应用程序，旨在获取JSON对象数组并将其呈现在listview中。我的web服务工作正常。我正在使用retrofit2获取POJO类，如下所示：

public static UnicsAgencyApi getUnicsAgencyApi() {

        if (sUnicsAgencyApi == null) {
            retrofit = new Retrofit.Builder().baseUrl(ENDPOINT_URL).addConverterFactory(GsonConverterFactory.create())
                    .build();
            sUnicsAgencyApi = retrofit.create(UnicsAgencyApi.class);
        }
        return sUnicsAgencyApi;
    }

    public interface UnicsAgencyApi {

        @GET("api/uconnectservice/AllAgency")
        Call<ArrayList<AgencyModel>> getStreams();
    }

这是我打电话的地方：

public void ShowAllUnicsAgencyInfo() {

        // get prompts.xml view
        LayoutInflater layoutInflater = LayoutInflater.from(Homepage.this);
        final View promptView = layoutInflater.inflate(R.layout.view_agency_list, null);
        listView2 = (ListView) promptView.findViewById(R.id.list);
        // GET DATA FROM WEBSERVICE
        ArrayList<AgencyModel> AgencyList = null;

        AgencyList = DownloadAgencyData();

        **AgencyListAdapter mAdapter = new AgencyListAdapter(this, AgencyList);**
        listView2.setAdapter(mAdapter);

        // ListView Item Click Listener
        listView2.setOnItemSelectedListener(new CustomOnItemSelectedListener() {

            public void onItemSelected(AdapterView<?> parent, View view, int pos, long id) {
                Toast.makeText(parent.getContext(),
                        "OnItemSelectedListener : " + parent.getItemAtPosition(pos).toString(), Toast.LENGTH_SHORT)
                        .show();

            }
        });

        final AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(Homepage.this);
        alertDialogBuilder.setView(promptView);

        // setup a dialog window
        alertDialogBuilder.setCancelable(false).setNeutralButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id) {

            }
        });
        // create an alert dialog
        AlertDialog alert = alertDialogBuilder.create();
        alert.show();

    }

    public ArrayList<AgencyModel> DownloadAgencyData() {

        RestApi.getUnicsAgencyApi().getStreams().enqueue(new Callback<ArrayList<AgencyModel>>() {

            @Override
            public void onFailure(Call<ArrayList<AgencyModel>> arg0, Throwable arg1) {
                // TODO Auto-generated method stub

                Log.e("Error in parsing", arg0.toString());

            }

            @Override
            public void onResponse(Call<ArrayList<AgencyModel>> AgencyModelData,
                    Response<ArrayList<AgencyModel>> response) {
                // TODO Auto-generated method stub
                mstreamData = new ArrayList<AgencyModel>();
                // ADD TO List here!!!!!!!!
                // Log.e("Response", "" + response.body().size());
                **mstreamData.addAll(response.body());**

            }

        });
        return mstreamData;
    }

但是我不断得到的错误来自自定义数组适配器getCount（）方法，通过以下Logcat：

 01-03 02:48:41.615: E/test(30453): Exception
    01-03 02:48:41.635: E/AndroidRuntime(30453): FATAL EXCEPTION: main
    01-03 02:48:41.635: E/AndroidRuntime(30453): Process: com.nickSoft.unics_alpha, PID: 30453
    01-03 02:48:41.635: E/AndroidRuntime(30453): java.lang.NullPointerException
    01-03 02:48:41.635: E/AndroidRuntime(30453):    at com.nickSoft.unics_alpha.AgencyListAdapter.getCount(AgencyListAdapter.java:26)
    01-03 02:48:41.635: E/AndroidRuntime(30453):    at android.widget.ListView.setAdapter(ListView.java:480)
    01-03 02:48:41.635: E/AndroidRuntime(30453):    at com.nickSoft.unics_alpha.Homepage.ShowAllUnicsAgencyInfo(Homepage.java:546)

我似乎无法确定我哪里出错，任何可能是错误的指导或解决此问题的更好方法都非常感谢，欢呼

Answer 1

RestApi.getUnicsAgencyApi（）。getStreams（）。enqueue方法更可能在thread上工作。所以下载...方法返回数据将不正确。你可以在onResponse方法中调用bakc结果。

Answer 2

我猜你的AgencyList没有实例化，或者即使在调用

之后也指向null

AgencyList = DownloadAgencyData();

在该行添加断点以进行调试。

由于您的列表视图取决于来自网络服务的数据，因此在调用setAdapter();之前检查是否收到数据是好的 -

if(AgencyList !=null){
 **AgencyListAdapter mAdapter = new AgencyListAdapter(this, AgencyList);**
        listView2.setAdapter(mAdapter);
} else{ Log.d(TAG,"AgencyList is null");

编辑：看看这是否有帮助设置多次访问数据的尝试。

for( int retry=0; AgencyList!=null && retry <10; retry++){ AgencyList = DownloadAgencyData(); }

Custom Adapter getCount方法中的空指针异常

2 个答案: