Question

数据库访问

问题：更改Firebase数据库中的数据或在我将“疾病：”食物中毒“添加到每个节点时获取实例时，它会停止工作。我的代码已正确同步以访问数据库，最后一个密钥为“疾病”。因此，当将“疾病”作为叶节点添加到每个其他节点并再次运行代码时，它会显示“应用程序已停止”。

SymptomActivity.java

package com.example.nishantsikri.microdoctor;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.Snackbar;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.Spinner;
import android.widget.TextView;

import android.widget.Toast;

import com.google.firebase.database.ChildEventListener;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import java.security.SecurityPermission;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;


public class SymptomActivity extends AppCompatActivity {


private DatabaseReference mFirebaseDatabase, spinnerDatabase;
private FirebaseDatabase mFirebaseInstance;
Button button;
TextView textView,symptom1,symptom2,symptom3;
Spinner spinner,spinner2,spinner3;
String textSymptom1,textSymptom2,textSymptom3;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_symptom);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);

    button = (Button) findViewById(R.id.button8);
    textView = (TextView) findViewById(R.id.textView2);

    symptom1 = (TextView) findViewById(R.id.symptom1);
    symptom2 = (TextView) findViewById(R.id.symptom2);
    symptom3 = (TextView) findViewById(R.id.symptom3);
    spinner = (Spinner) findViewById(R.id.spinner1);
    spinner2 = (Spinner) findViewById(R.id.spinner2);
    spinner3 = (Spinner) findViewById(R.id.spinner3);

    FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);
    fab.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                    .setAction("Action", null).show();
        }
    });
    FirebaseDatabase.getInstance().setPersistenceEnabled(true);


    // Write a message to the database
    mFirebaseInstance = FirebaseDatabase.getInstance();
    // store app title to 'app_title' node
    mFirebaseInstance.getReference("app_title").setValue("microDoctor");
    mFirebaseDatabase = mFirebaseInstance.getReference("symptomList");
    spinnerDatabase = mFirebaseInstance.getReference("symptomView");
    //mFirebaseDatabase.child("Headache").child("Some Value").setValue("Head");
    //mFirebaseDatabase.setValue("Headache");


    spinnerData();
    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
            textSymptom1 = spinner.getItemAtPosition(i).toString();
        }

        @Override
        public void onNothingSelected(AdapterView<?> adapterView) {

        }
    });
    spinner2.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
            textSymptom2 = spinner2.getItemAtPosition(i).toString();
        }

        @Override
        public void onNothingSelected(AdapterView<?> adapterView) {

        }
    });
    spinner3.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
        @Override
        public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
            textSymptom3 = spinner3.getItemAtPosition(i).toString();
        }

        @Override
        public void onNothingSelected(AdapterView<?> adapterView) {

        }
    });

    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            readDataListener();
        }
    });
}

private void readDataListener() {
    mFirebaseDatabase.child(textSymptom1).child(textSymptom2).child(textSymptom3).addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            Symptom symptom = dataSnapshot.getValue(Symptom.class);

            // Check for null
            if (symptom == null) {
                Log.e("Data", "Symptom data is null!");
                return;
            }

            Log.e("Symptom Data", "User data is changed!"+symptom.getDisease());

            // Display newly updated name and email
            textView.setText(symptom.disease+"\n"+dataSnapshot.getKey());
        }

        @Override
        public void onCancelled(DatabaseError error) {
            // Failed to read value
            Log.e("Error", "Failed to read user", error.toException());
        }
    });
}
private void spinnerData() {
    spinnerDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {

            Log.e("Spinner Data", "Spinner data is changed!");

            //DataSnapshot data = dataSnapshot;
            Iterable<DataSnapshot> temp = dataSnapshot.getChildren();
            ArrayList<String> list = new ArrayList<>();
//                list.add(dataSnapshot.getValue().toString());
//                showDataInSpinner(list);
            for (DataSnapshot lists : temp){
                Log.d("ddd","Array List: "+lists.getValue().toString());
                list.add(lists.getValue().toString());
                textView.setText(lists.getValue().toString());
            }
            showDataInSpinner(list);

        }

        @Override
        public void onCancelled(DatabaseError error) {
            // Failed to read value
            Log.e("Error", "Failed to read user", error.toException());
        }
    });
}
public void showDataInSpinner(ArrayList<String> data) {
    ArrayAdapter<String> adapter = new ArrayAdapter<>(
            this, android.R.layout.simple_spinner_item, data
    ); //Create the Adapter to set the data
    adapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item); //Set the layout resource to create the drop down views.
    spinner.setAdapter(adapter); //Set the data to your spinner
    spinner2.setAdapter(adapter);
    spinner3.setAdapter(adapter);
}
}

logcat的

11-10 23:28:57.985 27635-27640/com.example.nishantsikri.microdoctor I/art: Do partial code cache collection, code=51KB, data=61KB
11-10 23:28:57.985 27635-27640/com.example.nishantsikri.microdoctor I/art: After code cache collection, code=51KB, data=61KB
11-10 23:28:57.985 27635-27640/com.example.nishantsikri.microdoctor I/art: Increasing code cache capacity to 256KB
11-10 23:29:06.787 27635-27635/com.example.nishantsikri.microdoctor D/AndroidRuntime: Shutting down VM
11-10 23:29:06.788 27635-27635/com.example.nishantsikri.microdoctor E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                  Process: com.example.nishantsikri.microdoctor, PID: 27635
                                                                                  com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.example.nishantsikri.microdoctor.Symptom
                                                                                      at com.google.android.gms.internal.zzekp.zzb(Unknown Source)
                                                                                      at com.google.android.gms.internal.zzekp.zza(Unknown Source)
                                                                                      at com.google.firebase.database.DataSnapshot.getValue(Unknown Source)
                                                                                      at com.example.nishantsikri.microdoctor.SymptomActivity$6.onDataChange(SymptomActivity.java:127)
                                                                                      at com.google.android.gms.internal.zzeex.zza(Unknown Source)
                                                                                      at com.google.android.gms.internal.zzegs.zzbwg(Unknown Source)
                                                                                      at com.google.android.gms.internal.zzegy.run(Unknown Source)
                                                                                      at android.os.Handler.handleCallback(Handler.java:751)
                                                                                      at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                      at android.os.Looper.loop(Looper.java:154)
                                                                                      at android.app.ActivityThread.main(ActivityThread.java:6236)
                                                                                      at java.lang.reflect.Method.invoke(Native Method)
                                                                                      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:891)
                                                                                      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:781)

Answer 1

您正在尝试获取disease的{{1}}值，以便获取它，使用

String

或

String symptom = dataSnapshot.child("disease").getValue(String.class);

更改后，Firebase数据库无法正常同步

1 个答案: