我有一个列表视图，显示来自Web服务的值。它加载listview时很好。但是，当我点击任何项目打开一个新片段（显示该项目的详细信息）并返回到相同的列表视图时，其项目每次都会翻倍。例如，如果我（原始）总共有5个项目。然后当我从片段返回时，总计数将是10，然后是15，依此类推。这意味着该应用程序一次又一次地添加所有项目。我搜索了解决方案并做了像adapter.notifyDataSetChanged()这样的通用解决方案，但它仍然是重复的。如果有人能告诉我这个问题，我将不胜感激。
public class CustomListAdapter extends ArrayAdapter<Model> {
private Context mContext;
int resource;
private ArrayList<Model> mListData = new ArrayList<Model>();
public CustomListAdapter(Context mContext, int resource, ArrayList<Model> mListData) {
super(mContext, resource, mListData);
this.resource = resource;
this.mContext = mContext;
this.mListData = mListData;
}
public void setListData(ArrayList<Model> mListData) {
this.mListData = mListData;
notifyDataSetChanged();
}
@Override
public int getCount() {
return super.getCount();
}
@Override
public View getView(final int position, View convertView, final ViewGroup parent) {
View v = convertView;
final ViewHolder holder;
if (v == null) {
holder = new ViewHolder();
LayoutInflater inflater = ((Activity) mContext).getLayoutInflater();
v = inflater.inflate(resource, parent, false);
holder.custname = (TextView) v.findViewById(R.id.cust_name);
holder.date = (TextView) v.findViewById(R.id.date);
holder.staffname = (TextView) v.findViewById(R.id.staff_name);
holder.time = (TextView) v.findViewById(R.id.time);
holder.service = (TextView) v.findViewById(R.id.service);
holder.refid = (TextView) v.findViewById(R.id.refid);
v.setTag(holder);
} else {
holder = (ViewHolder) v.getTag();
}
final Model item = mListData.get(position);
holder.custname.setText(item.getCustname());
holder.date.setText(item.getDate());
holder.staffname.setText(item.getStaffname());
holder.time.setText(item.getTime());
holder.service.setText(item.getService());
holder.refid.setText(item.getRefid());
return v;
}
class ViewHolder {
TextView custname, date, staffname, time, service, refid;
}
}public class ListFrag extends Fragment{
private SwipeMenuListView listView;
private CustomListAdapter adapter;
private CShowProgress cShowProgress;
private SQLiteHandler db;
private String uid, bookingId;
private ArrayList<Model> arrayList = new ArrayList<>();
private static final String BOOKED_LIST = "http://192.168.220.13/android/showbookinglist";
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
return inflater.inflate(R.layout.listfrag, container, false);
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
listView = (SwipeMenuListView)view.findViewById(R.id.list);
db = new SQLiteHandler(getActivity());
cShowProgress = CShowProgress.getInstance();
fetchDetails();
adapter = new CustomListAdapter(getActivity(), R.layout.listitem, arrayList);
listView.setAdapter(adapter);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
String a = arrayList.get(i).getCustname();
String b = arrayList.get(i).getStaffname();
String c = arrayList.get(i).getService();
String d = arrayList.get(i).getDate();
String e = arrayList.get(i).getTime();
String f = arrayList.get(i).getRefid();
String g = arrayList.get(i).getEmail();
String h = arrayList.get(i).getServprice();
String j = arrayList.get(i).getSpeclprice();
String k = arrayList.get(i).getStatus();
db.addDetails(a, b, c, d, e, f, g, h, j, k);
DetailsView details = new DetailsView();
((Bookings)getActivity()).replaceFragment(details);
}
});
}
private void fetchDetails() {
cShowProgress.showProgress(getActivity());
StringRequest stringRequest = new StringRequest(Request.Method.POST, BOOKED_LIST,
new Response.Listener<String>() {
@Override
public void onResponse(String response) {
cShowProgress.hideProgress();
try {
JSONArray jsonArray = new JSONArray(response);
for(int i=0; i<jsonArray.length(); i++){
JSONObject obj = jsonArray.getJSONObject(i);
Model model = new Model();
model.setCustname(obj.getString("customername"));
model.setDate(obj.getString("staffdate"));
model.setStaffname(obj.getString("staffname")+"(Staff)");
model.setTime(obj.getString("stafftime"));
model.setService(obj.getString("servicename"));
model.setRefid(obj.getString("booking_referenceid"));
model.setEmail(obj.getString("customeremail"));
model.setServprice(obj.getString("serviceprice"));
model.setSpeclprice(obj.getString("specialprice"));
model.setStatus(obj.getString("status"));
model.setBookid(obj.getString("bookingid"));
arrayList.add(model);
}
adapter.notifyDataSetChanged();
} catch (JSONException e) {
// JSON error
e.printStackTrace();
Toast.makeText(getActivity(), "Json error: " + e.getMessage(), Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
Toast.makeText(getActivity(), "VolleyError" + error.toString(), Toast.LENGTH_LONG).show();
}
}) {
@Override
protected Map<String, String> getParams() {
Map<String, String> params = new HashMap<String, String>();
params.put("spaid", "145");
return params;
}
};
RequestQueue requestQueue = Volley.newRequestQueue(getActivity());
requestQueue.add(stringRequest);
}
}
答案 0 :(得分：2)
尝试将其更改为.. B＆＃39;因为您正在添加以前创建的列表中的元素。所以您必须清除它。
private void fetchDetails() {
if(arrayList!=null )arrayList.clear(); // this line
cShowProgress.showProgress(getActivity());
答案 1 :(得分：0)
问题是，当你回到片段时，它会被重新创建并再次调用 onViewCreated 。从那里再次调用 fetchDetails（），然后您将第二次将整个List添加到适配器。因此，您可以在 fetchDetails（）之前清除列表，或者只是必须再次获取它们。
答案 2 :(得分：0)
通过以下方式更改onResponse方法的try-catch块。
try {
JSONArray jsonArray = new JSONArray(response);
arrayList = new ArrayList<>();
for(int i=0; i<jsonArray.length(); i++)
{
JSONObject obj = jsonArray.getJSONObject(i);
Model model = new Model();
model.setCustname(obj.getString("customername"));
model.setDate(obj.getString("staffdate"));
model.setStaffname(obj.getString("staffname")+"(Staff)");
model.setTime(obj.getString("stafftime"));
model.setService(obj.getString("servicename"));
model.setRefid(obj.getString("booking_referenceid"));
model.setEmail(obj.getString("customeremail"));
model.setServprice(obj.getString("serviceprice"));
model.setSpeclprice(obj.getString("specialprice"));
model.setStatus(obj.getString("status"));
model.setBookid(obj.getString("bookingid"));
arrayList.add(model);
}
adapter.notifyDataSetChanged();
答案 3 :(得分：0)
这种情况正在发生，因为您没有清除arrayList。因此，每次构造数组和适配器时，都要将元素添加到已经包含元素的数组中。
这就是为什么你有5，然后是10，然后是15等等......
在添加新元素之前清除数组
arrayList.clear();
或者编制另一种策略，例如：