我是通用的firebase数据库和firebase的新手,在尝试使用它时遇到了一些小问题。DataSnapshot.getValue()不能正确检索对象
我使用下面的JSON代码我从火力控制台进口的,原来我刚刚创建的火力控制台数据库结构,那么下载的JSON代码,并如下:
{
"rides" : {
"arrive" : "kech",
"depart" : "agadir",
"detail" : "0,1",
"msg" : false,
"phone" : true,
"price" : 15,
"profile_id" : 0,
"spots" : 3,
"timedate" : "11/12/2017 11:15",
"vocal_id" : 0
}
}
对象我想取回被命名为Ride.java:
public class Ride {
private String arrive;
private String depart;
private String detail;
private boolean msg;
private boolean phone;
private int price;
private int profile_id;
private int spots;
private String timedate;
private int vocal_id;
public Ride() {}
// public getters (I created them I just didn't post it all to make the post shorter)
}
听我的数据库引用我使用下面的代码:
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("rides").child("0"); // 0 is the ride id
ref.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for(DataSnapshot singleSnapshot : dataSnapshot.getChildren()){
Ride ride = singleSnapshot.getValue(Ride.class);
rides.add(ride); // list of rides used later in a listadapter
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
Log.e(TAG, "onCancelled", databaseError.toException());
}
});
我试图从firebase数据库获取一个单骑,并在我的应用程序中显示它。在firebase控制台它有网址:https://myapp.firebaseio.com/rides/0(第二骑有ID 1等)。抓住所有游乐设施的最佳做法是什么?从每个游乐设施获取其属性是什么?
编辑:当我删除.child("0")
我没有得到任何错误,但没有出现在我的ListView 。显然rides.add(ride)
不会出于某种原因。
我加入的一个简单的实例骑的addListenerForSingleValueEvent()
方法外测试它,它工作正常。
我也试过改变听者addValueEventListener()
,相同的结果..
EDIT2:我得到一个错误信息,当我尝试从我的数据库中检索的整数。
我在我的数据库监听尝试这样做:
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot singleSnapshot: dataSnapshot.getChildren()) {
int price = (int) singleSnapshot.child("price").getValue(); // error takes place here
Log.d("FirebaseDb", String.valueOf(price));
}
}
结果是这样的错误:(所有整数)
java.lang.ClassCastException: java.lang.Long cannot be cast to java.lang.Integer
at com.ride.ive.anas.iveride.Fragments.RidesFragment$1.onDataChange(RidesFragment.java:96)
但是,当我取回一个字符串或布尔它工作正常,如:
String arrive = (String) singleSnapshot.child("arrive").getValue();
或者Boolean usePhone = (Boolean) singleSnapshot.child("phone").getValue();
EDIT3:这里是经@Prodigy请求RidesFragment.java文件。 其中我有一个ListView
,我尝试显示存储在我的firebase数据库中的所有乘车实例。
public class RidesFragment extends Fragment {
ListView list;
RidesAdapter2 ridesAdapter;
List<Ride> rides;
Ride ride;
List<RidePojo> filteredRides;
LinearLayout layoutFilter;
boolean filtersVisible = false;
boolean searchDone = false;
String userNumber;
public RidesFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_rides, container, false);
getActivity().setTitle("Search for a ride:");
// filter action button stuff
setHasOptionsMenu(true);
layoutFilter = rootView.findViewById(R.id.ll_filter_screen);
/*FragmentManager fm = getActivity().getSupportFragmentManager();
fm.popBackStack(null, FragmentManager.POP_BACK_STACK_INCLUSIVE);*/
ridesAdapter = new RidesAdapter2(getContext(), rides);
Bundle arguments = getArguments();
list = rootView.findViewById(R.id.rides_list);
rides = new ArrayList<>();
FirebaseDatabase database = FirebaseDatabase.getInstance();
DatabaseReference ref = database.getReference("rides");
ref.addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot singleSnapshot: dataSnapshot.getChildren()) {
Ride ride = singleSnapshot.getValue(Ride.class);
rides.add(ride);
ridesAdapter.notifyDataSetChanged();
Log.d("FbDatabase", singleSnapshot.toString());
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
Log.e(TAG, "onCancelled", databaseError.toException());
}
});
rides.add(ride);
// In case the rides ArrayList is not empty another fragment appears for no rides criteria
if(rides.isEmpty()) {
rootView = inflater.inflate(R.layout.fragment_empty, container, false);
Button rideButton = rootView.findViewById(R.id.btn_post_ride);
Button requestButton = rootView.findViewById(R.id.btn_post_request);
rideButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
launchFragment(new OfferRideFragment(), getActivity());
}
});
requestButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
launchFragment(new RequestFragment(), getActivity());
}
});
}
else {
list.setAdapter(ridesAdapter);
}
return rootView;
}
protected void launchFragment(Fragment f, FragmentActivity a) {
android.support.v4.app.FragmentTransaction fragmentTransaction =
a.getSupportFragmentManager().beginTransaction();
fragmentTransaction.replace(R.id.fragment_container, f);
fragmentTransaction.commit();
}
// ....
}
创建getter和为你的旅程类的东西其余制定者编辑的代码可以从这个stackoverflower答案[这里](https://stackoverflow.com/questions/30933328/how遵循-to-convert-firebase-data-to-java-object) –
我创建了它们,我只是不想将它们写在这里以使文章更短 – Anas
将代码添加到数据库引用的监听器的代码 –