创建了一个接口来获取 Arraylist 但仍然为空

【问题标题】：Created an interface To get Arraylist but still getting null创建了一个接口来获取 Arraylist 但仍然为空
【发布时间】：2014-06-30 06:50:48
【问题描述】：

在我的应用程序中，我想在其他类中使用异步类中的 ArrayList。因此，我创建了一个接口。但是当我在其他类中使用该接口时，我将 ArrayList 的大小设为 0。arraylist我在其他类中使用的是将其提供给自定义适配器以显示列表。但是由于我的 Arraylist 大小为 0，因此正在显示空白列表

异步类

public class SearchJobAsync extends AsyncTask<String, String, String> implements GetArrayList {
    private String response;
    Context c;
    SearchModel data;
    ArrayList<SearchModel> values;
    GetArrayList getArrayList;

    public SearchJobAsync(Context c, GetArrayList getArrayList) {
        this.c = c;
        this.getArrayList = getArrayList;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute ();
        CommonFunctions.showProgress (c, "Please Wait...", true);

    }

    @Override
    protected void onPostExecute(String s) {
        values = new ArrayList<SearchModel> ();

        super.onPostExecute (s);
        if (!s.trim ().contains ("Table")) {
            Crouton.makeText ((android.app.Activity) c, "Nothing found", Style.INFO).show ();
        } else {
            try {

                JSONObject jsonObject = new JSONObject (s);
                JSONObject NewDataSet = jsonObject.getJSONObject ("NewDataSet");
                if (NewDataSet.get ("Table") instanceof JSONObject) {
                    JSONObject table = NewDataSet.getJSONObject ("Table");
                    data = new SearchModel (table.getString ("Job_Category"), table.getString ("Min_Exp"), table.getString ("Max_Exp"), table.getString ("Posted_On"), table.getString ("Candidate_Counts"), table.getString ("Applications"), table.getString ("No_Of_Pos"), table.getString ("Job_Desc"), table.getString ("Job_Type"), table.getString ("Job_Hours"), table.getString ("Job_Status"), table.getString ("Job_Exp_Date"), table.getString ("Address"), table.getString ("Gender_Name"), table.getString ("Religion_Name"), table.getString ("Exp_Summary"), table.getString ("IJob_Request_ID"), table.getString ("Requestor_Name"));
                    values.add (data);
                    if(values.size()>0){
                        getArrayList.getList(values);
                    }
                } else if (NewDataSet.get ("Table") instanceof JSONArray) {
                    JSONArray tableArray = NewDataSet.getJSONArray ("Table");

                    for (int i = 0; i < tableArray.length (); i++) {
                        JSONObject table = tableArray.getJSONObject (i);
                        data = new SearchModel (table.getString ("Job_Category"), table.getString ("Min_Exp"), table.getString ("Max_Exp"), table.getString ("Posted_On"), table.getString ("Candidate_Counts"), table.getString ("Applications"), table.getString ("No_Of_Pos"), table.getString ("Job_Desc"), table.getString ("Job_Type"), table.getString ("Job_Hours"), table.getString ("Job_Status"), table.getString ("Job_Exp_Date"), table.getString ("Address"), table.getString ("Gender_Name"), table.getString ("Religion_Name"), table.getString ("Exp_Summary"), table.getString ("IJob_Request_ID"), table.getString ("Requestor_Name"));
                        values.add (data);
                        if(values.size()>0){
                            getArrayList.getList(values);
                        }

                    }

                }



            } catch (JSONException e) {
                e.printStackTrace ();
            }
        }


        CommonFunctions.showProgress (c, "", false);
        Intent i = new Intent (c, SearchJobListActivity.class);
        c.startActivity (i);
    }

    @Override
    protected String doInBackground(String... s) {
        response = HttpRequest.post ("https://beta135.hamarisuraksha.com/web/WebService/HsJobService.asmx/FindJobForVendor").send ("Vendor_IEntity_Code=" + "34588A34-E969-4723-84FE-E5409B66A5B7" + "&Job_Code=" + "&Job_Category=1" + "&Exp_Years_From=0" + "&Exp_Months_From=0" + "&Exp_Years_To=0" + "&Exp_Months_To=0").body ();
        response = response.replaceAll ("<[^>]*>", "").replaceAll ("\n", "");
        Log.e ("Search Jobs", "" + response);
        return response;
    }


    @Override
    public void getList(ArrayList<SearchModel> data) {
       values=data;
    }
}

界面

public interface GetArrayList  {

public void getList(ArrayList<SearchModel> data);
}

我使用 ArrayList 的类

public class SearchJobList extends ListFragment implements GetArrayList {
    private View view;
    private ListView lvSearchJobs;
    private ArrayList<SearchModel> value;
    SearchJobCustomList customList;
    SearchJobAsync searchJobAsync;
    private Context c;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        view = inflater.inflate (R.layout.search_job_lists, container, false);
        return view;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated (savedInstanceState);
        c = getActivity ();
        lvSearchJobs = (ListView) getActivity ().findViewById (android.R.id.list);
        value = new ArrayList<SearchModel> ();
        searchJobAsync = new SearchJobAsync (c,this);
        customList = new SearchJobCustomList (c, value);
        setListAdapter (customList);
//        searchJobAsync.execute ();


    }

    @Override
    public void getList(ArrayList<SearchModel> data) {
        value=data;

    }
}

【问题讨论】：

  • 为什么在 onPostExecute() 中启动 SearchJobListActivity ？
  • @Haresh 那么我该从哪里开始？？？
  • 您要做的是在 SearchJobList 片段上执行 SearchJobAsync，当数据来自响应时，尝试在您的 SearchJobList 片段上显示结果是它还是其他？
  • 是的，你是对的，但是为了让数据显示在列表中，我想要异步类中的 ArrayList
  • 不要在 onPostExecute() 中启动 SearchJobListActivity 使用 onItemClickListener 进行列表视图并在 setListAdapter (customList) 处初始化您的适配器；在 onPostExecute()...

标签： java android interface android-asynctask


【解决方案1】：

你可能应该这样定义你的界面：

public interface GetArrayList  {    
  List<SearchModel> getList();
}

那么你可以像这样返回一个列表对象：

@Override
public List<SearchModel> getList() {
    return Collections.unmodifiableList(value);
}

您当前的界面很奇怪，但如果您的实现是合理的，它可以工作。目前，您的 getList() 实现就像一个 setter 而不是 getter。你可以这样做：

@Override
public void getList(ArrayList<SearchModel> data) {
    data.clear();
    data.addAll(value);
}

最后说明：GetArrayList 是一个奇怪的接口名称。通常接口应该以描述性的方式命名，而不是直接在它们持有的方法之后。例如，您可以调用您的接口ListHolder 或SearchModelCatalogue。

【讨论】：

  • @Anuj Simply values = getArrayList.getList();.
  • 先生，我照你说的做了，但我得到空指针异常
  • @Anuj 很难在没有看到调整后的代码的情况下提出建议。在SearchJobList.onActivityCreated() 之前调用SearchJobList.getList() 的任何可能性？如果发生这种情况，您的列表为空。
【解决方案2】：

试试这个方法，希望能帮助你解决问题。

public class SearchJobList extends ListFragment {
    private View view;
    private ListView lvSearchJobs;
    private ArrayList<SearchModel> value;
    SearchJobCustomList customList;
    SearchJobAsync searchJobAsync;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        view = inflater.inflate (R.layout.search_job_lists, container, false);
        return view;
    }

    @Override
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated (savedInstanceState);
        lvSearchJobs = (ListView) getActivity ().findViewById (android.R.id.list);
        new SearchJobAsync(getActivity(),new GetArrayList() {
            @Override
            public void getList(ArrayList<SearchModel> data) {
                value = data;
                customList = new SearchJobCustomList (c, value);
                setListAdapter (customList);
            }
        }).execute();
    }

}

public class SearchJobAsync extends AsyncTask<String, String, String> {
    private Context c;
    private String response;
    SearchModel data;
    ArrayList<SearchModel> values;
    GetArrayList getArrayList;

    public SearchJobAsync(Context c, GetArrayList getArrayList) {
        this.c = c;
        this.getArrayList = getArrayList;
    }

    @Override
    protected void onPreExecute() {
        super.onPreExecute ();
        CommonFunctions.showProgress (c, "Please Wait...", true);

    }

    @Override
    protected void onPostExecute(String s) {
        values = new ArrayList<SearchModel> ();

        super.onPostExecute (s);
        if (!s.trim ().contains ("Table")) {
            Crouton.makeText ((android.app.Activity) c, "Nothing found", Style.INFO).show ();
        } else {
            try {

                JSONObject jsonObject = new JSONObject (s);
                JSONObject NewDataSet = jsonObject.getJSONObject ("NewDataSet");
                if (NewDataSet.get ("Table") instanceof JSONObject) {
                    JSONObject table = NewDataSet.getJSONObject ("Table");
                    data = new SearchModel (table.getString ("Job_Category"), table.getString ("Min_Exp"), table.getString ("Max_Exp"), table.getString ("Posted_On"), table.getString ("Candidate_Counts"), table.getString ("Applications"), table.getString ("No_Of_Pos"), table.getString ("Job_Desc"), table.getString ("Job_Type"), table.getString ("Job_Hours"), table.getString ("Job_Status"), table.getString ("Job_Exp_Date"), table.getString ("Address"), table.getString ("Gender_Name"), table.getString ("Religion_Name"), table.getString ("Exp_Summary"), table.getString ("IJob_Request_ID"), table.getString ("Requestor_Name"));
                    values.add (data);
                } else if (NewDataSet.get ("Table") instanceof JSONArray) {
                    JSONArray tableArray = NewDataSet.getJSONArray ("Table");

                    for (int i = 0; i < tableArray.length (); i++) {
                        JSONObject table = tableArray.getJSONObject (i);
                        data = new SearchModel (table.getString ("Job_Category"), table.getString ("Min_Exp"), table.getString ("Max_Exp"), table.getString ("Posted_On"), table.getString ("Candidate_Counts"), table.getString ("Applications"), table.getString ("No_Of_Pos"), table.getString ("Job_Desc"), table.getString ("Job_Type"), table.getString ("Job_Hours"), table.getString ("Job_Status"), table.getString ("Job_Exp_Date"), table.getString ("Address"), table.getString ("Gender_Name"), table.getString ("Religion_Name"), table.getString ("Exp_Summary"), table.getString ("IJob_Request_ID"), table.getString ("Requestor_Name"));
                        values.add (data);
                    }
                }

            } catch (JSONException e) {
                e.printStackTrace ();
            }
            CommonFunctions.showProgress (c, "Please Wait...",false);
            getArrayList.getList(values);
        }
    }

    @Override
    protected String doInBackground(String... s) {
        response = HttpRequest.post ("https://beta135.hamarisuraksha.com/web/WebService/HsJobService.asmx/FindJobForVendor").send ("Vendor_IEntity_Code=" + "34588A34-E969-4723-84FE-E5409B66A5B7" + "&Job_Code=" + "&Job_Category=1" + "&Exp_Years_From=0" + "&Exp_Months_From=0" + "&Exp_Years_To=0" + "&Exp_Months_To=0").body ();
        response = response.replaceAll ("<[^>]*>", "").replaceAll ("\n", "");
        Log.e ("Search Jobs", "" + response);
        return response;
    }

}

【讨论】：

  • 我按照你说的做了，但我不会去 ListActivity，它仍然在同一页面上
猜你喜欢
  • 2023-04-01
  • 1970-01-01
  • 1970-01-01
  • 2013-05-16
  • 2022-12-15
  • 1970-01-01
  • 2019-11-05
  • 1970-01-01
  • 2019-10-09
相关资源
最近更新 更多
热门标签
Java Python linux javascript Mysql C# Docker 算法 前端 SpringBoot Redis Vue spring 设计模式 .net core .net kubernetes c++ 数据库 数据结构 大数据 js 机器学习 微服务 Android Go 程序员 面试 JVM ASP.net core 云原生 人工智能 后端 PHP git CSS golang k8s Nginx Django mybatis 深度学习 多线程 React 架构 devops 爬虫 云计算 Spring Boot LeetCode