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我发现当下面的URL添加到数据库时会出现问题。你会如何保存它以便不会发生错误？
大家好我收到错误无法退回到com.firebase.client.DataSnapshot.getValue类型。它在这里的代码，但我不知道如何解决它：
Person person = postSnapshot.getValue(Person.class);
以下是完整代码：
MainActivity
package uk.co.jaunt_app.jaunt;
import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;
import com.crashlytics.android.answers.Answers;
import com.crashlytics.android.answers.CustomEvent;
import com.firebase.client.DataSnapshot;
import com.firebase.client.Firebase;
import com.firebase.client.FirebaseError;
import com.firebase.client.ValueEventListener;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
import java.util.ArrayList;
import java.util.List;
import static uk.co.jaunt_app.jaunt.R.id.Posts;
public class MainActivity extends AppCompatActivity {
private FloatingActionButton addmap;
private Button settingbtn;
private TextView mNameTextView;
private TextView mEmailTextView;
ListView mPosts;
private DrawerLayout mDrawerLayout;
private ActionBarDrawerToggle mDrawerToggle;
private CharSequence mDrawerTitle;
private CharSequence mTitle;
ArrayAdapter<String> adapter;
private FirebaseAuth auth;
private ArrayList<feed> feedPop = new ArrayList<>();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
getSupportActionBar().setDisplayShowHomeEnabled(true);
getSupportActionBar().setLogo(R.drawable.jauntlogodark);
getSupportActionBar().setDisplayUseLogoEnabled(true);
setContentView(R.layout.activity_main);
Firebase.setAndroidContext(this);
Firebase ref = new Firebase(Config.FIREBASE_URL);
FirebaseUser currentFirebaseUser = FirebaseAuth.getInstance().getCurrentUser();
String uid = currentFirebaseUser.getUid();
Firebase usersRef = ref.child("Users").child(uid).child("name");
Firebase emailRef = ref.child("Users").child(uid).child("email");
Firebase postRef = ref.child("Users").child(uid).child("Maps");
postRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot snapshot) {
for (final DataSnapshot postSnapshot : snapshot.getChildren()) {
//Getting the data from snapshot
Person person = postSnapshot.getValue(Person.class);
final String mapName = person.getMapName();
final String mapid = person.getMapID();
final String mapStartLat = person.getStartLat();
final String mapStartLong = person.getStartLong();
final String mapEndLat = person.getEndLat();
final String mapEndLong = person.getEndLong();
adapter.notifyDataSetChanged();
feedPop.add(
new feed(mapName, mapStartLat, mapStartLong, mapEndLat, mapEndLong));
final ArrayAdapter<feed> adapter = new feedArrayAdapter(MainActivity.this, 0, feedPop);
ListView listView = (ListView) findViewById(R.id.customListView1);
listView.setAdapter(adapter);
listView.setItemsCanFocus(true);
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
Intent intent = new Intent(MainActivity.this, ViewUserMapActivity.class);
intent.putExtra("mapName", feedPop.get(position).getFeedName().toString());
intent.putExtra("mapStartLat", feedPop.get(position).getFeedStartLat().toString());
intent.putExtra("mapStartLong", feedPop.get(position).getFeedStartLong().toString());
intent.putExtra("mapEndLat", feedPop.get(position).getFeedEndLat().toString());
intent.putExtra("mapEndLong", feedPop.get(position).getFeedEndLong().toString());
startActivity(intent);
}
});
}
}
@Override
public void onCancelled(FirebaseError firebaseError) {
Toast.makeText(getApplicationContext(),
"Cancelled", Toast.LENGTH_LONG)
.show();
}
});
adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1);
mPosts = (ListView) findViewById(Posts);
mPosts.setAdapter(adapter);
List<Nav> navList= new ArrayList<Nav>();
navList.add(new Nav("Profile"));
navList.add(new Nav("Feed"));
navList.add(new Nav("Maps"));
navList.add(new Nav("Most Popular"));
navList.add(new Nav("Settings"));
navList.add(new Nav("Report a Bug"));
ArrayAdapter<Nav> navadapter = new ArrayAdapter<Nav>(this,android.R.layout.simple_list_item_1, navList);
final ListView lv= (ListView) findViewById(R.id.left_drawer);
lv.setAdapter(navadapter);
lv.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
int itemPosition = position;
switch(itemPosition) {
case 0:
Intent menuItem = new Intent(MainActivity.this, UserProfileActivity.class);
startActivity(menuItem);
break;
case 1:
menuItem = new Intent(MainActivity.this, MainActivity.class);
startActivity(menuItem);
break;
case 2:
menuItem = new Intent(MainActivity.this, UserMapActivity.class);
startActivity(menuItem);
break;
case 3:
menuItem = new Intent(MainActivity.this, UserMapActivity.class);
startActivity(menuItem);
break;
case 4:
menuItem = new Intent(MainActivity.this, SettingsActivity.class);
startActivity(menuItem);
break;
case 5:
menuItem = new Intent(MainActivity.this, UserMapActivity.class);
startActivity(menuItem);
break;
}
}
});
mNameTextView = (TextView) findViewById(R.id.NameTextView);
usersRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String name = dataSnapshot.getValue(String.class);
mNameTextView.setText(name);
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
});
mEmailTextView = (TextView) findViewById(R.id.EmailTextView);
emailRef.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
String email = dataSnapshot.getValue(String.class);
mEmailTextView.setText(email);
}
@Override
public void onCancelled(FirebaseError firebaseError) {
}
});
addmap = (FloatingActionButton) findViewById(R.id.add_map);
addmap.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Answers.getInstance().logCustom(new CustomEvent("Added Map"));
Intent intent = new Intent(MainActivity.this, MapStartActivity.class);
startActivity(intent);
}
});
settingbtn = (Button) findViewById(R.id.settingbtn);
settingbtn.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this, SettingsActivity.class);
startActivity(intent);
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater inflater = getMenuInflater();
inflater.inflate(R.menu.activity_menu_drawer, menu);
return true;
}
}
//custom ArrayAdapter
class feedArrayAdapter extends ArrayAdapter<feed>{
private Context context;
private List<feed> feedPop;
//constructor, call on creation
public feedArrayAdapter(Context context, int resource, ArrayList<feed> objects) {
super(context, resource, objects);
this.context = context;
this.feedPop = objects;
}
//called when rendering the list
public View getView(int position, View convertView, ViewGroup parent) {
feed feed = feedPop.get(position);
//get the inflater and inflate the XML layout for each item
LayoutInflater inflater = (LayoutInflater) context.getSystemService(Activity.LAYOUT_INFLATER_SERVICE);
View view = inflater.inflate(R.layout.feed_listview, null);
TextView others = (TextView) view.findViewById(R.id.others);
TextView mapname = (TextView) view.findViewById(R.id.address);
//set address and description
String completeOthers = feed.getFeedStartLat() + ", " + feed.getFeedStartLong() + ", " + feed.getFeedEndLat() + ", " + feed.getFeedEndLong();
others.setText(completeOthers);
//set address and description
String completeAddress = feed.getFeedName();
mapname.setText(completeAddress);
return view;
}
}
完整错误代码：
Fatal Exception: com.firebase.client.FirebaseException: Failed to bounce to type
at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:185)
at uk.co.jaunt_app.jaunt.MainActivity$1.onDataChange(MainActivity.java:76)
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$1.run(EventRaiser.java:38)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6776)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)
Caused by com.fasterxml.jackson.databind.JsonMappingException: Can not instantiate value of type [simple type, class uk.co.jaunt_app.jaunt.Person] from String value; no single-String constructor/factory method
at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator._createFromStringFallbacks(StdValueInstantiator.java:428)
at com.fasterxml.jackson.databind.deser.std.StdValueInstantiator.createFromString(StdValueInstantiator.java:299)
at com.fasterxml.jackson.databind.deser.BeanDeserializerBase.deserializeFromString(BeanDeserializerBase.java:1056)
at com.fasterxml.jackson.databind.deser.BeanDeserializer._deserializeOther(BeanDeserializer.java:136)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:123)
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 uk.co.jaunt_app.jaunt.MainActivity$1.onDataChange(MainActivity.java:76)
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$1.run(EventRaiser.java:38)
at android.os.Handler.handleCallback(Handler.java:751)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:154)
at android.app.ActivityThread.main(ActivityThread.java:6776)
at java.lang.reflect.Method.invoke(Method.java)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1520)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1410)