Question

这里我试图从数据库中获取值并将它们列在ListView中，但在20个项目之后我想在用户滚动到ListView结束时向ListView添加更多项目，但是当用户滚动到结尾时ListView被完全删除，并添加新项目。但是我需要在上一个List本身的末尾添加新项目......

这是我的Android代码：

这将在onCreate（）

执行

  public void getLocalJobs() {
    empty.setVisibility(TextView.GONE);
    String url = ConfigCuboid.GET_JOBS_LOCAL;
    String url1 = Tags;
    String URL = url + url1;
    StringRequest stringRequest = new StringRequest(URL, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            showJSONLocal(response);
        }
    },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {

                }
            });
    RequestQueue requestQueue = Volley.newRequestQueue(this);
    requestQueue.add(stringRequest);
}

@TargetApi(Build.VERSION_CODES.M)
private void showJSONLocal(String response) {
    ParseJSONLocal pj = new ParseJSONLocal(response);
    pj.parseJSONLocal();

    CustomListLocal c1 = new CustomListLocal(this, ParseJSONLocal.job_local_id, ParseJSONLocal.user_names, ParseJSONOnline.job_typess, ParseJSONLocal.job_titles, ParseJSONLocal.job_works,
            ParseJSONLocal.job_dates, ParseJSONLocal.job_months, ParseJSONLocal.job_years,
            ParseJSONLocal.job_times, ParseJSONLocal.job_periods, ParseJSONLocal.job_areas, ParseJSONLocal.job_rates,
            ParseJSONLocal.user_ids, ParseJSONLocal.job_detailss, ParseJSONLocal.image, ParseJSONLocal.regtoken
            , ParseJSONLocal.verify);
    listViewWork.setAdapter(c1);
    Toast.makeText(getApplicationContext(),"ListNo=="+CustomListLocal.LastLocalJobId,Toast.LENGTH_SHORT).show();


    if (c1.isEmpty()) {
        empty.setVisibility(TextView.VISIBLE);
        pb.setVisibility(ProgressBar.GONE);
    }
    listViewWork.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int poss, long id) {
            Intent is = new Intent(getApplicationContext(), WorkProfileLocal.class);
            is.putExtra("Positions", poss);
            startActivity(is);
        }
    });


    listViewWork.setOnScrollListener(new AbsListView.OnScrollListener() {

        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {

        }

        @Override
        public void onScroll(AbsListView view,
                             int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            //Algorithm to check if the last item is visible or not
            final int lastItem = firstVisibleItem + visibleItemCount;
            if (lastItem == totalItemCount) {
                // you have reached end of list, load more data
               // Toast.makeText(getApplicationContext(),"ListIsOver",Toast.LENGTH_SHORT).show();
                Toast.makeText(getApplicationContext(),"ListNo=="+CustomListLocal.LastLocalJobId,Toast.LENGTH_SHORT).show();
                LoadLocalList();
            }

        }


    });
}

在ListView结束时执行此方法：

   public void LoadLocalList(){

    empty.setVisibility(TextView.GONE);
    String url = ConfigCuboid.GET_LOADED_JOBS_LOCAL;
    String urll1="last_local_job_id=";
    String  urll11 = CustomListLocal.LastLocalJobId;
    String urll="&job_title[]=";
    String url1 = Tags;

    String URL = url + urll1+urll11+urll+url1;
    StringRequest stringRequest = new StringRequest(URL, new Response.Listener<String>() {

        @Override
        public void onResponse(String response) {
            showJSONLocall(response);
        }
    },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {

                }
            });
    RequestQueue requestQueue = Volley.newRequestQueue(this);
    requestQueue.add(stringRequest);
}

@TargetApi(Build.VERSION_CODES.M)
private void showJSONLocall(String response) {
    ParseJSONLocal pj = new ParseJSONLocal(response);
    pj.parseJSONLocal();

    CustomListLocal c2 = new CustomListLocal(this, ParseJSONLocal.job_local_id, ParseJSONLocal.user_names, ParseJSONOnline.job_typess, ParseJSONLocal.job_titles, ParseJSONLocal.job_works,
            ParseJSONLocal.job_dates, ParseJSONLocal.job_months, ParseJSONLocal.job_years,
            ParseJSONLocal.job_times, ParseJSONLocal.job_periods, ParseJSONLocal.job_areas, ParseJSONLocal.job_rates,
            ParseJSONLocal.user_ids, ParseJSONLocal.job_detailss, ParseJSONLocal.image, ParseJSONLocal.regtoken
            , ParseJSONLocal.verify);
    listViewWork.setAdapter(c2);
    Toast.makeText(getApplicationContext(),"ListNo=="+CustomListLocal.LastLocalJobId,Toast.LENGTH_SHORT).show();


    if (c2.isEmpty()) {
        empty.setVisibility(TextView.VISIBLE);
        pb.setVisibility(ProgressBar.GONE);
    }
    listViewWork.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int poss, long id) {
            Intent is = new Intent(getApplicationContext(), WorkProfileLocal.class);
            is.putExtra("Positions", poss);
            startActivity(is);
        }
    });


}

Answer 1

此行重置整个列表

listViewWork.setAdapter(c2);

您可以直接添加到ArrayAdapter的任何实例，并且一次只能在ListView中有一个适配器。

换句话说，在onCreate中设置一个适配器，然后在其他任何地方添加到该适配器。不要再次调用setAdapter，并且当您调用adapter.add时，您将保留所有数据并且ListView将更新

我还建议您减少重复的代码。还不清楚为什么有两个单独的URL正在加载数据

如何在android中向ListView添加项目

1 个答案: