[英]Android - Firebase - Failed to convert value of type java.util.HashMap to String
[英]Firebase android error “Failed to convert value of type ”
該代碼在啟動時崩潰;
E / AndroidRuntime:致命例外:主進程:com.example.manya.eventspage,PID:2974 com.google.firebase.database.DatabaseException:無法將com.google.android中類型java.util.HashMap的值轉換為String com.google.android.gms.internal.zzamy.zzb(未知來源)的com.google.android.gms.internal.zzamy.zzc(未知來源)的com.google.android.gms.internal.zzamy.zzb(未知來源)的com com.example.manya.eventspage.Events $ 1.onDataChange(Events.java:46)的com.google.android.gms.internal.zzajp.zza(Unknown的.google.firebase.database.DataSnapshot.getValue(未知源)來源)com.google.android.gms.internal.zzakp.zzcxi(來源不明)com.google.android.gms.internal.zzaks $ 1.run(來源不明)android.os.Handler.handleCallback(Handler。 java:751)位於android.os.Handler.dispatchMessage(Handler.java:95)位於android.os.Looper.loop(Looper.java:154)位於android.app.ActivityThread.main(ActivityThread.java:6077)位於com.android.internal.os.Z上的java.lang.reflect.Method.invoke(本地方法) ygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:865)在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
該代碼是
package com.example.manya.eventspage;
import android.app.DatePickerDialog;
import android.app.TimePickerDialog;
import android.content.Context;
import android.content.Intent;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import java.text.*;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.List;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.widget.*;
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;
public class Events extends AppCompatActivity {
private TextView t;
private static ListView l;
private static ArrayAdapter<String> adapter;
final static ArrayList<String> arrayList = new ArrayList<String>();
FirebaseDatabase database=FirebaseDatabase.getInstance();
protected DatabaseReference myRef;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_events);
t = (TextView) findViewById(R.id.textView3);
l = (ListView) findViewById(R.id.list_view);
myRef=database.getReference().child("events");
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String val=dataSnapshot.child("events").getValue(String.class);
arrayList.add(val);
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
// Adapter: You need three parameters 'the context, id of the layout (it will be where the data is shown),
// and the array that contains the data
adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_spinner_item, arrayList);
l.setAdapter(adapter);
}
protected void onResume()
{
super.onResume();
Intent in=getIntent();
if(in.hasExtra(Intent.EXTRA_TEXT))
{
String d=in.getStringExtra(Intent.EXTRA_TEXT);
final DatabaseReference postsRef = database.getReference().child("events");
DatabaseReference newPostRef = postsRef.push();
newPostRef.setValue(new event(d));
arrayList.add(d);
// next thing you have to do is check if your adapter has changed
adapter.notifyDataSetChanged();
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.menu, menu);
return true;
}
public boolean onOptionsItemSelected(MenuItem item) {
int id = item.getItemId();
if (id == R.id.add_event) {
Context context=Events.this;
Class destclass=addevent.class;
Intent str=new Intent(context,destclass);
startActivity(str);
return true;
}
return super.onOptionsItemSelected(item);
}
json數據是
{
"events" : {
"events" : {
"-KkfUKAYAriWN7NYqTcx" : {
"event_detail" : "21 05 2017, 20:20TextView"
}
}
}
}
您的代碼無法處理以下事實:您在/events/events
下有一個事件列表。 要正確處理此問題,您有兩種方法:
ValueEventListener
並遍歷子節點 ChildEventListener
第一個最接近您當前的代碼,只是增加了一個額外的循環:
myRef=database.getReference().child("events/events"); // note the change in path
myRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
String val=childSnapshot.getValue(String.class);
arrayList.add(val);
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
throw databaseError.toException(); // don't ignore errors
}
});
第二種方法告訴Firebase處理其SDK中的列表並顯示每個子對象:
myRef=database.getReference().child("events/events"); // note the change in path
myRef.addChildEventListener(new ChildEventListener() {
@Override
public void onChildAdded(DataSnapshot dataSnapshot, String previousChildKey) {
String val=dataSnapshot.getValue(String.class);
arrayList.add(val);
}
...
});
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