我希望有人可以帮我解决问题。我有Android应用程序，有3个选项卡，我使用片段，第一个选项卡是recyclerView列表，第二个选项卡是地图。问题出现在选项卡1中，我需要使用volley获取数据到选项卡1上的recyclerView，如果运行正常但我看不到第一个应用程序启动时的数据，但是当我更改选项卡并再次返回选项卡1时它将刷新数据并在recyclerView上显示数据。
Adapter.java
public class CustomListAdapterWarkop extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
private Context context;
private List<Warkop> mWarkop;
private LayoutInflater inflater;
public CustomListAdapterWarkop(Context context, List<Warkop> mWarkop) {
this.context=context;
inflater= LayoutInflater.from(context);
this.mWarkop = mWarkop;
}
@Override
public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = inflater.inflate(R.layout.list_warkop_row, parent, false);
ItemViewHolder holder = new ItemViewHolder(view);
return holder;
}
@Override
public void onBindViewHolder(RecyclerView.ViewHolder holder, int position) {
ItemViewHolder viewHolder = (ItemViewHolder) holder;
Warkop current = mWarkop.get(position);
viewHolder.tvNamaWarkop.setText(current.getNamaWarkop());
ImageLoader imageLoader = ImageLoader.getInstance();
DisplayImageOptions options = new DisplayImageOptions.Builder().cacheInMemory(true)
.cacheOnDisc(true).resetViewBeforeLoading(true)
.showImageForEmptyUri(R.drawable.noimage)
.showImageOnFail(R.drawable.noimage)
.showImageOnLoading(R.drawable.noimage).build();
imageLoader.displayImage(current.getFotoWarkop(), viewHolder.ivFotoWarkop, options);
}
@Override
public int getItemCount() {
return mWarkop.size();
}
}
ItemHolder.java
package com.andylah.warkopedia;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;
/**
* Created by andylah on 11/3/2017.
*/
public class ItemViewHolder extends RecyclerView.ViewHolder {
public ImageView ivFotoWarkop;
public TextView tvNamaWarkop;
public ItemViewHolder(View itemView) {
super(itemView);
tvNamaWarkop = itemView.findViewById(R.id.nama_warkop);
ivFotoWarkop = itemView.findViewById(R.id.image_warkop);
}
}
Tab 1.java
public class tabSatu extends Fragment {
private static final String TAG = tabDua.class.getSimpleName();
public static final int CONNECTION_TIMEOUT = 10000;
public static final int READ_TIMEOUT = 15000;
private boolean isFragmentLoaded = false;
View vTabSatu;
private RecyclerView recyclerView;
public static List<Warkop> warkopList = new ArrayList<Warkop>();
private CustomListAdapterWarkop warkopAdapter;
public tabSatu(){
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
new AsyncFetch().execute();
vTabSatu = inflater.inflate(R.layout.tabsatu_view, container, false);
recyclerView = vTabSatu.findViewById(R.id.warkop_container);
LinearLayoutManager layoutManager = new LinearLayoutManager(getActivity());
recyclerView.setLayoutManager(layoutManager);
Log.d("LOG : ", "onCreatedView Run");
// Inflate the layout for this fragment
return vTabSatu;
}
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
warkopAdapter = new CustomListAdapterWarkop(getActivity(), warkopList);
warkopAdapter.notifyDataSetChanged();
recyclerView.setAdapter(warkopAdapter);
Log.d("LOG : ", "onViewCreated Run");
}
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser && !isFragmentLoaded ) {
// Load your data here or do network operations here
isFragmentLoaded = true;
//new AsyncFetch().execute();
}else{
isFragmentLoaded = false;
Log.d("LOG : ", "isFragmentLoaded = false");
}
}
private class AsyncFetch extends AsyncTask<String, String, String> {
ProgressDialog pDialog = new ProgressDialog(getActivity());
HttpURLConnection conn;
URL url = null;
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog.setMessage("Loading list warkop ...");
pDialog.setCancelable(false);
pDialog.show();
}
@Override
protected String doInBackground(String... strings) {
try {
// Enter URL address where your json file resides
// Even you can make call to php file which returns json data
url = new URL(AppConfig.LOAD_WARKOP);
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return e.toString();
}
try {
// Setup HttpURLConnection class to send and receive data from php and mysql
conn = (HttpURLConnection) url.openConnection();
conn.setReadTimeout(READ_TIMEOUT);
conn.setConnectTimeout(CONNECTION_TIMEOUT);
conn.setRequestMethod("POST");
// setDoOutput to true as we recieve data from json file
conn.setDoOutput(true);
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
return e1.toString();
}
try {
int response_code = conn.getResponseCode();
// Check if successful connection made
if (response_code == HttpURLConnection.HTTP_OK) {
// Read data sent from server
InputStream input = conn.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(input));
StringBuilder result = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
// Pass data to onPostExecute method
return (result.toString());
} else {
return ("unsuccessful");
}
} catch (IOException e) {
e.printStackTrace();
return e.toString();
} finally {
conn.disconnect();
}
}
@Override
protected void onPostExecute(String result) {
pDialog.dismiss();
try{
JSONObject object = new JSONObject(result);
String getObject = object.getString("warkop");
JSONArray jsonArray = new JSONArray(getObject);
boolean error = object.getBoolean("error");
if(!error){
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
Warkop warkop = new Warkop();
warkop.setNamaWarkop(jsonObject.getString("nama_warkop"));
warkop.setAlamatWrkop(jsonObject.getString("alamat_warkop"));
warkop.setKotaWarkop(jsonObject.getString("kota_warkop"));
warkop.setLatWarkop(Double.parseDouble(jsonObject.getString("lat_warkop")));
warkop.setLangWarkop(Double.parseDouble(jsonObject.getString("long_warkop")));
warkop.setIsWifi(Integer.parseInt(jsonObject.getString("is_wifi")));
warkop.setIsToilet(Integer.parseInt(jsonObject.getString("is_toilet")));
warkop.setIsTv(Integer.parseInt(jsonObject.getString("is_tv")));
warkop.setIsColokan(Integer.parseInt(jsonObject.getString("is_colokan")));
warkop.setIsParkir(Integer.parseInt(jsonObject.getString("is_parkir")));
warkop.setFotoWarkop(jsonObject.getString("foto_warkop"));
warkopList.add(warkop);
}
}else{
String errorMsg = object.getString("error_msg");
Toast.makeText(getContext(),
errorMsg, Toast.LENGTH_LONG).show();
}
}catch (JSONException e) {
e.printStackTrace();
Toast.makeText(getActivity(), "Json error: " + e.getMessage(), Toast.LENGTH_LONG).show();
}
}
}
}
答案 0 :(得分：3)
问题：即使您拨打notifyDataSetChanged()，但适配器中没有数据。
@Override
public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
warkopAdapter = new CustomListAdapterWarkop(getActivity(), warkopList);
warkopAdapter.notifyDataSetChanged();
recyclerView.setAdapter(warkopAdapter);
}
因此，您需要在API调用后设置并warkopList通知Adapter。它会对你有所帮助。
tabSatu：
@Override
protected void onPostExecute(String result) {
pDialog.dismiss();
try {
JSONObject object = new JSONObject(result);
String getObject = object.getString("warkop");
JSONArray jsonArray = new JSONArray(getObject);
boolean error = object.getBoolean("error");
if (!error) {
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
Warkop warkop = new Warkop();
...
warkopList.add(warkop);
adapter.setItems(warkopList);
}
}
...
}
CustomListAdapterWarkop：将setItem()方法添加到适配器
public class CustomListAdapterWarkop extends RecyclerView.Adapter<RecyclerView.ViewHolder> {
...
public void setItems(List<WarkopList> warkopList) {
mWarkop = warkopList;
notifyDataSetChanged();
}
...
}