Clear Android ListView

问题

I have a ListView. I want to dynamically change the contents of the listview.I used "adapter.notifyDataSetChanged();" to change the contents. I have also tried setting the adapter of the listview to null but still I get the same results. It is refreshing but not clearing the listview, instead it is appending it with the previous results. What i want is the previous contents should be deleted and the new results should be displayed.

I am not able to understand where is my mistake and what i am missing.

I would be Thankful if someone could please help me out with this.

Below is the code that generates the listview

 public void ListDrawer() {
     try {
      JSONObject jsonResponse = new JSONObject(jsonResult);
      JSONArray jsonMainNode = jsonResponse.optJSONArray("myRegisteredList");

      for (int i = 0; i < jsonMainNode.length(); i++) {
       JSONObject jsonChildNode = jsonMainNode.getJSONObject(i);
       String registered_name = jsonChildNode.optString("seminar");
       String org = jsonChildNode.optString("organizer");
       String sem_id = jsonChildNode.optString("id");
       String r_sem = jsonChildNode.optString("seminar_id");

       registeredlist = new HashMap<String, String>();
       registeredlist.put("registeredList", registered_name);
       registeredlist.put("seminar_id", r_sem);
       registeredlist.put("sem_id", sem_id);
       registeredlist.put("organizer", org);
       registeredList.add(registeredlist);

      }
     } catch (JSONException e) {
         //Toast.makeText(this, e.getMessage().toString() + " 1", Toast.LENGTH_LONG).show();
         Toast.makeText(ViewReservedSeminarList.this, "Sorry...You don't have any reserved seminar/s.", Toast.LENGTH_LONG).show();
    }
     try{

    simpleAdapter = new SimpleAdapter(this, registeredList,
       android.R.layout.simple_list_item_2,
       new String[] { "registeredList" ,"organizer", "seminar_id" }, new int[] { android.R.id.text1 , android.R.id.text2 , android.R.id.title });


     listView.setAdapter(simpleAdapter);
     listView.setOnItemClickListener(new OnItemClickListener(){

        @Override
        public void onItemClick(AdapterView<?> a, View v, int i, long l) {
            // TODO Auto-generated method stub
            @SuppressWarnings("unchecked")
            HashMap<String, String> selected_row = (HashMap<String, String>) simpleAdapter.getItem(i);
            s_id = selected_row.get("seminar_id");
            Intent intent = new Intent(ViewReservedSeminarList.this, ReservedSeminar.class);
            startActivity(intent);
            //Toast.makeText(ViewReservedSeminarList.this, "Selected Item : "+s_id, Toast.LENGTH_LONG).show();
        }

     });
     }catch(Exception e){
         //Toast.makeText(this, e.getMessage().toString() + " 2", Toast.LENGTH_LONG).show();
        Toast.makeText(ViewReservedSeminarList.this, "There is no data being fetched", Toast.LENGTH_LONG).show();
 }
}

Below is the snippet I placed on the onCreate method to refresh the listview every 10 seconds. I am calling the ListDrawer method under the accessWebService method.

 final Handler handler = new Handler();
                 handler.postDelayed( new Runnable(){
                        @Override
                        public void run(){
                        accessWebService();
                        handler.postDelayed(this, 10 * 1000);
                        Log.i("TAG", "notify");

                 }
                        }, 10 * 1000

                        ); 

回答1:

Try this please:

Clear the arraylist/HashMap

Add new items

adapter.notifyDataSetChanged();

set adapter.

回答2:

If you use an ArrayAdapter instead of a SimpleAdapter you can call

ArrayAdapter.clear();
ArrayAdapter.notifyDataSetChanged();

To remove all the elements from the adapter.

回答3:

Try This

final Handler handler = new Handler();
                 handler.postDelayed( new Runnable(){
                        @Override
                        public void run(){
                 //this line i have added in your code
                         registeredList.clear();
                        accessWebService();
                        handler.postDelayed(this, 10 * 1000);
                        Log.i("TAG", "notify");

                 }
                        }, 10 * 1000

                        ); 

回答4:

remove adapter.notifyDataSetChanged(); hope it works

来源：https://stackoverflow.com/questions/22954679/clear-android-listview