如何使用 Firebase 实时数据库中的关联节点名称列表填充“微调器”？

Question

Let's say I have the following firebase realtime database structure:

{
    "Object1" : {
        "A" : "exampleData",
        "B" : "exampleData",
        "C" : "exampleData",
        "D" : "exampleData"
    }
}

I'm trying to get a list of associated node names from "Object1". I'm trying Inflate Spinner (which is part of my layout.xml) with this list of associated node names. The spinner will therefore contain items to choose from: A, B, C, D

I'm trying like this: (Just a snippet)

@Override
protected void onCreate(@Nullable Bundle savedInstanceState {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.MyActivity);

      Spinner spinner = findViewById(R.id.MySpinner);
      database = FirebaseDatabase.getInstance();
      dbRef = database.getReference("Object1");

      dbRef.addValueEventListener(new ValueEventListener() {
           @Override
           public void onDataChange (@NonNull DataSnapshot dataSnapshot) {
                ArrayList<String> arrList = new ArrayList<String>();
                    for (DataSnapshot snap : dataSnapshot.getChildren()) {
                        arrList.add(snap.getKey());
                    }

                    ArrayAdapter<String> arrAdapter = new ArrayAdapter<String>(MyActivity.this,R.layout.MyActivity, arrList);
                    spinner.setAdapter(arrAdapter);
          }
      });
}

After running this activity, the application "crashes" and an error occurs. If necessary, I am also able to supply an extract from LogCat.

Expectation: Retrieve a list of nodes associated with Object1, populate the spinner with this list.

Here is a report from Logcat:

(just errors)

E/RunLoop: Uncaught exception in Firebase Database runloop (3.0.0). Please report to firebase-database-client@google.com
java.lang.NoClassDefFoundError: com.google.firebase.database.android.AndroidAuthTokenProvider$3
    at com.google.firebase.database.android.AndroidAuthTokenProvider.produceIdTokenListener(com.google.firebase:firebase-database@@16.0.4:85)
    at com.google.firebase.database.android.AndroidAuthTokenProvider.addTokenChangeListener(com.google.firebase:firebase-database@@16.0.4:80)
    at com.google.firebase.database.core.Repo.deferredInitialization(com.google.firebase:firebase-database@@16.0.4:109)
    at com.google.firebase.database.core.Repo.access$000(com.google.firebase:firebase-database@@16.0.4:55)
    at com.google.firebase.database.core.Repo$1.run(com.google.firebase:firebase-database@@16.0.4:94)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:423)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:154)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:269)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
    at java.lang.Thread.run(Thread.java:818)

Answer 1

You have supplied the layout file of your activity in

  ArrayAdapter<String> arrAdapter = new ArrayAdapter<String>(MyActivity.this,R.layout.MyActivity, arrList);

The Second argument of the ArrayAdapter<>() requires a resource ID of a TextView as stated in the Error Message

java.lang.IllegalStateException: ArrayAdapter requires the resource ID to be a TextView

You can use R.layout.support_simple_spinner_dropdown_item instead as below

ArrayAdapter<String> arrAdapter = new ArrayAdapter<String>(MyActivity.this,R.layout.support_simple_spinner_dropdown_item,arrList);