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我有一個問題，很多人都有，但我不明白我該如何擺脫它。請在我的情況下幫助我，不要標記爲重複。我有一個與firebase鏈接在一個片段的recyclerview。 我必須檢索「承認人」後面的所有物品。 所有的項目在裏面都有一些文字瀏覽，從數據庫中寫入一些字符串。但是當我嘗試在數據庫中檢索項目我得到的錯誤：com.google.firebase.database.DatabaseException：無法將java.lang.String類型的對象轉換爲參考
com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.ji.architettiadvisor.Data.Recensione at com.google.android.gms.internal.zzbqi.zze(Unknown Source) at com.google.android.gms.internal.zzbqi.zzb(Unknown Source) at com.google.android.gms.internal.zzbqi.zza(Unknown Source) at com.google.firebase.database.DataSnapshot.getValue(Unknown Source) at com.ji.architettiadvisor.DisplayStudio$PlaceholderFragment.getUpdates(DisplayStudio.java:337) at com.ji.architettiadvisor.DisplayStudio$PlaceholderFragment.access$000(DisplayStudio.java:233) at com.ji.architettiadvisor.DisplayStudio$PlaceholderFragment$1.onChildAdded(DisplayStudio.java:358) at com.google.android.gms.internal.zzblz.zza(Unknown Source) at com.google.android.gms.internal.zzbnz.zzYj(Unknown Source) at com.google.android.gms.internal.zzboc$1.run(Unknown Source) at android.os.Handler.handleCallback(Handler.java:739) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5461) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
這裏是我的Recensione.class：
public class Recensione {
private String Commento;
private String Rating;
private String Username;
private String Data;
public String getData() {
return Data;
}
public void setData(String data) {
Data = data;
}
public String getUsername() {
return Username;
}
public void setUsername(String username) {
Username = username;
}
public String getRating() {
return Rating;
}
public void setRating(String rating) {
Rating = rating;
}
public String getCommento() {
return Commento;
}
public void setCommento(String commento) {
Commento = commento;
}}
這裏我PlaceholderFragment/DisplayStudio.class：
public static class PlaceholderFragment extends Fragment implements OnMapReadyCallback {
private GoogleMap googleMapa;
/**
* The fragment argument representing the section number for this
* fragment.
*/
private static final String ARG_SECTION_NUMBER = "section_number";
public PlaceholderFragment() {
}
/**
* Returns a new instance of this fragment for the given section
* number.
*/
public static DisplayStudio.PlaceholderFragment newInstance(int sectionNumber) {
DisplayStudio.PlaceholderFragment fragment = new DisplayStudio.PlaceholderFragment();
Bundle args = new Bundle();
args.putInt(ARG_SECTION_NUMBER, sectionNumber);
fragment.setArguments(args);
return fragment;
}
RecyclerView rv;
MyCommentsAdapter adapter;
ArrayList<Recensione> recensioni = new ArrayList<>();
DatabaseReference mDatabase;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
Bundle bl = getArguments();
if (getArguments().getInt(ARG_SECTION_NUMBER)==1)
{
View rootView = inflater.inflate(R.layout.fragment_profilo, container, false);
Intent intent = getActivity().getIntent();
String desc = intent.getStringExtra("Desc");
final String names = intent.getStringExtra("Nome");
TextView test = (TextView) rootView.findViewById(R.id.nome);
TextView descr = (TextView) rootView.findViewById(R.id.desc);
TextView key = (TextView) rootView.findViewById(R.id.key);
test.setText(names);
descr.setText(desc);
String MyKey = bl.getString(MY_STUDIO_KEY);
key.setText(MyKey);
return rootView;
}
else if(getArguments().getInt(ARG_SECTION_NUMBER)==2)
{
Intent intent = getActivity().getIntent();
final String names = intent.getStringExtra("Nome");
//INITIALIZE FIREBASE
mDatabase = FirebaseDatabase.getInstance().getReference().child("Studi").child(names).child("valutazioni").child("recensioni");
mDatabase.keepSynced(true);
/* Ricarica tutte le opinioni */
refreshData();
View rootView = inflater.inflate(R.layout.fragment_opinioni, container, false);
rv = (RecyclerView) rootView.findViewById(R.id.MyRecView2s);
Recensione rc = new Recensione();
rc.setUsername("Luca");
rc.setCommento("Non male, da app");
rc.setRating("10");
rc.setData("oggi");
//ci vuole il push prima del setvalue
mDatabase.child(names).setValue(rc);
rv.setLayoutManager(new LinearLayoutManager(getActivity()));
return rootView;
}
else
{
View rootView = inflater.inflate(R.layout.fragment_maps, container, false);
SupportMapFragment mapFragment = SupportMapFragment.newInstance();
getChildFragmentManager().beginTransaction().replace(R.id.map , mapFragment).commit();
mapFragment.getMapAsync(this);
if (mapFragment == null) {
getChildFragmentManager().beginTransaction().replace(R.id.map , mapFragment).commit();
mapFragment.getMapAsync(this);
}
return rootView;
}
}
private void getUpdates(DataSnapshot dataSnapshot){
recensioni.clear();
for (DataSnapshot ds : dataSnapshot.getChildren()){
Recensione s=new Recensione();
s.setUsername(ds.getValue(Recensione.class).getUsername());
s.setCommento(ds.getValue(Recensione.class).getCommento());
s.setRating(ds.getValue(Recensione.class).getRating());
s.setData(ds.getValue(Recensione.class).getData());
recensioni.add(s);
}
if(recensioni.size()>0){
adapter=new MyCommentsAdapter(getActivity(), recensioni);
rv.setAdapter(adapter);
}else {
Toast.makeText(getActivity(),"NON CI SONO ANCORA OPINIONI.", Toast.LENGTH_LONG).show();
}
}
//RETRIEVE
private void refreshData(){
mDatabase.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String s) {
getUpdates(dataSnapshot);
}
@Override
public void onChildChanged(DataSnapshot dataSnapshot, String s) {
getUpdates(dataSnapshot);
}
@Override
public void onChildRemoved(DataSnapshot dataSnapshot) {
}
@Override
public void onChildMoved(DataSnapshot dataSnapshot, String s) {
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
}
@Override
public void onMapReady(GoogleMap googleMap) {
googleMapa = googleMap;
Intent intent = getActivity().getIntent();
final String names = intent.getStringExtra("Nome");
String posizione1 = intent.getStringExtra("Posizione1");
String posizione2 = intent.getStringExtra("Posizione2");
try
{
//Toast.makeText(MapsActivity.this,posizione1 + " " + posizione2 , Toast.LENGTH_LONG).show(); //not a double
Double protein = Double.parseDouble(posizione1);
Double protein2 = Double.parseDouble(posizione2);
LatLng sydney = new LatLng(protein,protein2); //custom icon in drawable
googleMap.addMarker(new MarkerOptions().position(sydney).title(names)/*.icon(BitmapDescriptorFactory.fromResource(R.drawable.cast_abc_scrubber_control_off_mtrl_alpha))*/);
googleMap.moveCamera(CameraUpdateFactory.newLatLngZoom(sydney, 12.0f));
}
catch(NumberFormatException e)
{
// Toast.makeText(DisplayStudio.this, e.toString() , Toast.LENGTH_LONG).show(); //not a double
}
}
}
/**
* A {@link FragmentPagerAdapter} that returns a fragment corresponding to
* one of the sections/tabs/pages.
*/
public class SectionsPagerAdapter extends FragmentPagerAdapter {
public SectionsPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
// getItem is called to instantiate the fragment for the given page.
// Return a PlaceholderFragment (defined as a static inner class below).
return DisplayStudio.PlaceholderFragment.newInstance(position + 1);
}
@Override
public int getCount() {
// Show 3 total pages.
return 3;
}
@Override
public CharSequence getPageTitle(int position) {
switch (position) {
case 0:
return "PROFILO";
case 1:
return "OPINIONI";
case 2:
return "MAPS";
}
return null;
}
}}
一切都在這個活動的底部。 每一個不同的「recensione」有其定製pubblished ID，這並不重要......
我怎樣才能解決這個問題？我真的不知道，我不明白什麼是錯的，抱歉，但我是新的。
Stack Overflow是一個非常低效的調試器。請將代碼減少到[重現問題所需的最小代碼]（http://stackoverflow.com/help/mcve）（請閱讀鏈接）。這個問題可能與您的活動，地圖，點擊或視圖無關，但完全取決於您在該位置附加「ChildEventListener」和JSON數據的位置。通過將您的代碼簡化爲重現問題所需的部分，您可以更輕鬆地爲您提供幫助，從而更有可能獲得幫助。 –