從下拉列表中選擇項目時，微調器不顯示任何值

Question

這是我的Java代碼

public class FragmentAssignTask extends Fragment {

ProgressDialog progressDialog;
DocumentReference dr;
CollectionReference cr = FirebaseFirestore.getInstance().collection("tasks");
SharedPreferences sp;

final List<String> tasks = new ArrayList<String>();
final List<String> users = new ArrayList<String>();
View myview;
Spinner sp1;
Spinner sp2;
Button btn;
ArrayAdapter<String> adp1,adp2;
public String jsonResponse;
public FragmentAssignTask() {
    // Required empty public constructor
}


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    myview = inflater.inflate(R.layout.fragment_assign_task, container, false);
    sp1 = (Spinner) myview.findViewById(R.id.spinner1);
    sp2 = (Spinner) myview.findViewById(R.id.spinner2);
    btn = myview.findViewById(R.id.btn_assignTask);
    progressDialog = new ProgressDialog(getActivity());
    progressDialog.setMessage("Syncing Tasks");
    progressDialog.show();
    initiaizeValues();
    sp1.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView arg0, View arg1, int position, long id) {
            sp1.setSelection(position);
        }
        @Override
        public void onNothingSelected(AdapterView<?> arg0) {
        }
    });

    sp2.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()
    {
        public void onItemSelected(AdapterView parent, View view, int position, long id)
        {
            String selectedItem = parent.getItemAtPosition(position).toString();
            sp2.setSelection(position);
        } // to close the onItemSelected
        public void onNothingSelected(AdapterView parent)
        {

        }
    });
    btn.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            try {
                String tn;
                if(sp1.isSelected())
                 tn = sp1.getSelectedItem().toString();
                String un ;
                if(sp2.isSelected())
                    un= sp2.getSelectedItem().toString();
                progressDialog.setMessage("Assigning Task");
                progressDialog.setCancelable(false);
                progressDialog.show();
                tn = "Task 2";
                un = "umar@gmail.com";
                String documentString = "clienttask/" + un + "/tasks/"+tn;
                dr = FirebaseFirestore.getInstance().document(documentString);
                Map<String, Object> data = new HashMap<String, Object>();
                data.put("status", "i");
                dr.set(data).addOnSuccessListener(new OnSuccessListener<Void>() {
                    @Override
                    public void onSuccess(Void aVoid) {
                        Toast.makeText(getActivity(),"Task Assigned Successfully",Toast.LENGTH_SHORT).show();
                        Log.d("assignTask", "task assigned to user");
                        progressDialog.dismiss();;
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Toast.makeText(getActivity(),"Failed!!!",Toast.LENGTH_SHORT).show();
                        Log.d("assignTask", "task not assigned");
                        progressDialog.dismiss();;
                    }
                });
            }catch (Exception ex)
            {
                progressDialog.dismiss();
                ex.toString();
            }
        }
    });
    return myview;
}
@Override
public void onStart()
{
    super.onStart();
}
public void initiaizeValues()
{
    try{
        cr.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
            @Override
            public void onSuccess(QuerySnapshot documentSnapshots) {
                if(!documentSnapshots.isEmpty())
                {
                    List<DocumentSnapshot> d = documentSnapshots.getDocuments();
                    DocumentSnapshot t;
                    String tname,description;
                    for(int i=0;i<d.size();i++)
                    {
                        t = d.get(i);
                        tname = t.getString("tname");
                        tasks.add(tname);
                    }
                }
                else
                {
                    Toast.makeText(getActivity(),"No Task !!!",Toast.LENGTH_LONG).show();
                }
            }
        });
        sp = getActivity().getSharedPreferences("trainer",Context.MODE_PRIVATE);
        String tid = sp.getString("trainerid","aun@gmail.com");
        String collectionstring = "clienttrainer/"+ tid+"/clients";
        cr = FirebaseFirestore.getInstance().collection(collectionstring);

        cr.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
            @Override
            public void onSuccess(QuerySnapshot documentSnapshots) {
                if(!documentSnapshots.isEmpty())
                {
                    List<DocumentSnapshot> d = documentSnapshots.getDocuments();
                    DocumentSnapshot t;
                    String cid;
                    for(int i=0;i<d.size();i++)
                    {
                        t = d.get(i);
                        cid = t.getString("name");
                        users.add(cid);
                    }
                    Toast.makeText(getActivity(),"Syncing Clients Sucessfull!!",Toast.LENGTH_SHORT).show();
                    progressDialog.dismiss();
                }
                else
                {
                    Toast.makeText(getActivity(),"No user assigned!!!",Toast.LENGTH_SHORT).show();
                    progressDialog.dismiss();
                }
            }
        });

    }catch(Exception ex)
    {
        int j = 0;
    }
    adp1 = new ArrayAdapter<String>(getActivity(),android.R.layout.simple_spinner_dropdown_item,tasks);
    adp2 = new ArrayAdapter<String>(getActivity(),android.R.layout.simple_spinner_dropdown_item,users);
    sp1.setAdapter(adp1);
    sp2.setAdapter(adp2);
}
}

Answer 1

您正在從Firebase Asynchronously獲取數據，並使用空列表創建Adapter 。

您必須在使用數據創建列表之后創建Adapter ，然后將適配器設置為Spinner 。 或在獲取數據並構建列表之后，使用notifyDataSetChanged()方法通知Adapter數據集更改。

對於Spinner ：

        cr.get().addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
        @Override
        public void onSuccess(QuerySnapshot documentSnapshots) {
            if(!documentSnapshots.isEmpty())
            {
                List<DocumentSnapshot> d = documentSnapshots.getDocuments();
                DocumentSnapshot t;
                String tname,description;
                for(int i=0;i<d.size();i++)
                {
                    t = d.get(i);
                    tname = t.getString("tname");
                    tasks.add(tname);
                }
            }
            else
            {
                Toast.makeText(getActivity(),"No Task !!!",Toast.LENGTH_LONG).show();
            }
            adp1 = new ArrayAdapter<String>(getActivity(),android.R.layout.simple_spinner_dropdown_item,tasks);
            sp1.setAdapter(adp1);
        }
    });

對第二個Spinner使用相同的方法。