尝试从Firebase获取数据时Android应用程序崩溃

Question

I am developing an Android app and have integrated Firebase into it. The connection is successful and writing to Firebase is not a problem, when the app tries to receive the data to display in the app, the app crashes. I have added my code below if anyone can help.

Capture_Meetings.java

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

import com.firebase.client.DataSnapshot;
import com.firebase.client.Firebase;
import com.firebase.client.FirebaseError;
import com.firebase.client.ValueEventListener;

public class Capture_Meetings extends AppCompatActivity {

private EditText editTextName;
private EditText editTextAddress;
private EditText editDateTime;
private TextView textViewPersons;
private Button buttonSave;

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

    Firebase.setAndroidContext(this);

    buttonSave = (Button) findViewById(R.id.buttonSave);
    editTextName = (EditText) findViewById(R.id.editTextName);
    editTextAddress = (EditText) findViewById(R.id.editTextAddress);
    editDateTime = (EditText) findViewById(R.id.editDateTime);

    textViewPersons = (TextView) findViewById(R.id.textViewPersons);

    buttonSave.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            //Creating firebase object
            Firebase ref = new Firebase(Config.FIREBASE_URL);

            //Getting values to store
            String name = editTextName.getText().toString().trim();
            String address = editTextAddress.getText().toString().trim();
            String DateTime = editDateTime.getText().toString().trim();

            //Creating Person object
            final MeetingUser person = new MeetingUser();

            //Adding values
            person.setName(name);
            person.setAddress(address);
            person.setDateTime(DateTime);

            //Storing values to firebase
            ref.child("Person").push().setValue(person);


            //Value event listener for realtime data update
            ref.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot snapshot)
                {
                    for (DataSnapshot postSnapshot : snapshot.getChildren()) {
                        //Getting the data from snapshot
                        MeetingUser person = postSnapshot.getValue(MeetingUser.class);

                        //Adding it to a string
                        String string = "\n Name of School: "+person.getName()+"\n Date and Time:"+ person.getDateTime()+"\nMeeting Notes: "+person.getAddress()+"\n\n";

                        //Displaying it on textview
                        textViewPersons.setText(string);
                    }
                }

                @Override
                public void onCancelled(FirebaseError firebaseError) {
                    System.out.println("The read failed: " + firebaseError.getMessage());
                }
            });

        }
    });
}
}

MeetingUser.java - constructor

public class MeetingUser {
//name and address string
private String Key;
private String name;
private String address;
private String DateTime;

public MeetingUser() {
  /*Blank default constructor essential for Firebase*/
}
//Getters and setters
public String getKey ()
{
    return Key;
}

public void setKey (String Key)
{
    this.Key = Key;
}
public String getName() {
    return name;
}

public void setName(String name) {
    this.name = name;
}

public String getAddress() {
    return address;
}

public void setAddress(String address) {
    this.address = address;
}

public String getDateTime()
{
    return DateTime;
}

public void setDateTime (String DateTime)
{
    this.DateTime = DateTime;
}
}

Crash Log :

com.firebase.client.FirebaseException: Failed to bounce to type
                      at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:185)
                      at com.example.pooveshin.saica_sgb.Capture_Meetings$1$1.onDataChange(Capture_Meetings.java:67)
                      at com.firebase.client.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:45)
                      at com.firebase.client.core.view.DataEvent.fire(DataEvent.java:45)
                      at com.firebase.client.core.view.EventRaiser$1.run(EventRaiser.java:38)
                      at android.os.Handler.handleCallback(Handler.java:739)
                      at android.os.Handler.dispatchMessage(Handler.java:95)
                      at android.os.Looper.loop(Looper.java:135)
                      at android.app.ActivityThread.main(ActivityThread.java:5254)
                      at java.lang.reflect.Method.invoke(Native Method)
                      at java.lang.reflect.Method.invoke(Method.java:372)
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
                   Caused by: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "-KVZjE7GFxVENXAnemZF" (class com.example.pooveshin.saica_sgb.MeetingUser), not marked as ignorable (4 known properties: , "name", "dateTime", "address", "key"])
                      at [Source: java.io.StringReader@20f5d5e1; line: 1, column: 26] (through reference chain: com.example.pooveshin.saica_sgb.MeetingUser["-KVZjE7GFxVENXAnemZF"])
                      at com.fasterxml.jackson.databind.DeserializationContext.reportUnknownProperty(DeserializationContext.java:555)
                      at com.fasterxml.jackson.databind.deser.std.StdDeserializer.handleUnknownProperty(StdDeserializer.java:708)
                      at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.handleUnknownProperty(BeanDeserializerBase.java:1160)
                      at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:315)
                      at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:121)
                      at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2888)
                      at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2034)
                      at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:183)
                      at com.example.pooveshin.saica_sgb.Capture_Meetings$1$1.onDataChange(Capture_Meetings.java:67) 
                      at com.firebase.client.core.ValueEventRegistration.fireEvent(ValueEventRegistration.java:45) 
                      at com.firebase.client.core.view.DataEvent.fire(DataEvent.java:45) 
                      at com.firebase.client.core.view.EventRaiser$1.run(EventRaiser.java:38) 
                      at android.os.Handler.handleCallback(Handler.java:739) 
                      at android.os.Handler.dispatchMessage(Handler.java:95) 
                      at android.os.Looper.loop(Looper.java:135) 
                      at android.app.ActivityThread.main(ActivityThread.java:5254) 
                      at java.lang.reflect.Method.invoke(Native Method) 
                      at java.lang.reflect.Method.invoke(Method.java:372) 
                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 

Answer 1

Have a look at this :

public void setKey (String Key)
{
    this.Key = Key;
}

When it gets deserialized Jackson assumes that the field is key but instead you wrote it as Key thus, it cannot be map to the object's field.

Change private String Key to private String key , the same with the DateTime , use lowercase fields if possible.