Firebase android错误“无法转换类型的值" [英] Firebase android error "Failed to convert value of type "
问题描述
此代码在启动时崩溃;
This code is crashing on start;
E/Android运行时:致命异常:主要 流程:com.example.manya.eventspage,PID:2974 com.google.firebase.database.DatabaseException:无法将类型java.util.HashMap的值转换为String 在com.google.android.gms.internal.zzamy.zzcg(未知来源) 在com.google.android.gms.internal.zzamy.zzb(未知来源) com.google.android.gms.internal.zzamy.zza上(未知来源) 位于com.google.firebase.database.DataSnapshot.getValue(未知来源) 在com.example.manya.eventspage.Events $ 1.onDataChange(Events.java:46) 在com.google.android.gms.internal.zzajp.zza(未知来源) com.google.android.gms.internal.zzakp.zzcxi(未知来源) com.google.android.gms.internal.zzaks $ 1.run(未知来源) 在android.os.Handler.handleCallback(Handler.java:751) 在android.os.Handler.dispatchMessage(Handler.java:95) 在android.os.Looper.loop(Looper.java:154) 在android.app.ActivityThread.main(ActivityThread.java:6077) 在java.lang.reflect.Method.invoke(本机方法) 在com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:865) 在com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
E/AndroidRuntime: FATAL EXCEPTION: main Process: com.example.manya.eventspage, PID: 2974 com.google.firebase.database.DatabaseException: Failed to convert value of type java.util.HashMap to String at com.google.android.gms.internal.zzamy.zzcg(Unknown Source) at com.google.android.gms.internal.zzamy.zzb(Unknown Source) at com.google.android.gms.internal.zzamy.zza(Unknown Source) at com.google.firebase.database.DataSnapshot.getValue(Unknown Source) at com.example.manya.eventspage.Events$1.onDataChange(Events.java:46) at com.google.android.gms.internal.zzajp.zza(Unknown Source) at com.google.android.gms.internal.zzakp.zzcxi(Unknown Source) at com.google.android.gms.internal.zzaks$1.run(Unknown Source) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6077) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:865) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:755)
代码为
the code is
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数据是
{
"events" : {
"events" : {
"-KkfUKAYAriWN7NYqTcx" : {
"event_detail" : "21 05 2017, 20:20TextView"
}
}
}
}
推荐答案
您的代码无法处理您在/events/events
下具有事件列表的事实.要正确处理此问题,您有两种方法:
Your code fails to take care of the fact that you have a list of events under /events/events
. To handle this correctly you have two approaches:
- 使用
ValueEventListener
并遍历子节点 - 使用
ChildEventListener
- Use a
ValueEventListener
and loop over the child nodes - Use a
ChildEventListener
第一个最接近您当前的代码,只是增加了一个额外的循环:
The first is closest to your current code and just adds an extra loop:
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
}
});
第二种方法告诉Firebase处理其SDK中的列表并显示每个子对象:
The second approach tells Firebase to handle the list in its SDK and surfaces each child:
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);
}
...
});
这篇关于Firebase android错误“无法转换类型的值"的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!