我正在尝试修改Firebase的Android聊天示例以包含Firebase时间戳值。我可以使用ServerValue.TIMESTAMP;发送时间戳，但是当Firebase尝试显示消息时，应用程序崩溃了。编辑：
发送我使用的消息
private void sendMessage() {
EditText inputText = (EditText)findViewById(R.id.messageInput);
String input = inputText.getText().toString();
Map timestamp = ServerValue.TIMESTAMP;
if (!input.equals("")) {
// Create our 'model', a Chat object
Chat chat = new Chat(name, input, timestamp, userID);
// Create a new, auto-generated child of that chat location, and save our chat data there
chatRef.push().setValue(chat);
inputText.setText("");
}
}
伪造的结构是这样的：
->Messenger
|--> room
|--> messages
|--> messageID
|--> from: "Name"
|--> text: "Message"
|--> timestamp: xxxxxxxxxxxxx
|--> userID: "id"
和Chat.java
public class Chat {
private String from;
private String text;
private int userID;
private Map<String, String> timestamp = new HashMap<String, String>();
// Required default constructor for Firebase object mapping
@SuppressWarnings("unused")
private Chat() { }
Chat(String from, String text, Map timestamp, int userID) {
this.from = from;
this.text = text;
this.timestamp = timestamp;
this.userID = userID;
}
public String getFrom() {
return from;
}
public String getText() {
return text;
}
public Map getTimestamp() {
return timestamp;
}
public int getuserID() {
return userID;
}
}
如果我从Firebase上的邮件中删除了时间戳字段，则该应用不会崩溃。
完整的错误消息如下：
08-26 15:08:08.223 18097-18097/com.firebase.androidchat E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.firebase.androidchat, PID: 18097
com.firebase.client.FirebaseException: Failed to bounce to type
at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:185)
at com.firebase.androidchat.FirebaseListAdapter$1.onChildAdded(FirebaseListAdapter.java:63)
at com.firebase.client.core.ChildListenerContainer$1.run(ChildListenerContainer.java:52)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
Caused by: com.shaded.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.LinkedHashMap out of VALUE_NUMBER_INT token
at [Source: java.io.StringReader@41f8c588; line: 1, column: 2] (through reference chain: com.firebase.androidchat.Chat["timestamp"])
at com.shaded.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:575)
at com.shaded.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:569)
at com.shaded.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:310)
at com.shaded.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:26)
at com.shaded.fasterxml.jackson.databind.deser.SettableBeanProperty.deserialize(SettableBeanProperty.java:464)
at com.shaded.fasterxml.jackson.databind.deser.impl.FieldProperty.deserializeAndSet(FieldProperty.java:107)
at com.shaded.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:295)
at com.shaded.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:121)
at com.shaded.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2888)
at com.shaded.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2034)
at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:181)
at com.firebase.androidchat.FirebaseListAdapter$1.onChildAdded(FirebaseListAdapter.java:63)
at com.firebase.client.core.ChildListenerContainer$1.run(ChildListenerContainer.java:52)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
看起来它可能是由另一个令我困惑的问题引起的......
Caused by: com.shaded.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.LinkedHashMap out of VALUE_NUMBER_INT token
at [Source: java.io.StringReader@41f8c588; line: 1, column: 2] (through reference chain: com.firebase.androidchat.Chat["timestamp"])
答案 0 :(得分：13)
Firebase.ServerValue.TIMESTAMP设置为地图（包含{.sv: "timestamp"}），告知Firebase使用服务器的时间填充该字段。当回读该数据时，它是实际的unix时间戳，它是Long。当Firebase（使用Jackson）尝试反序列化返回的值时，它会失败，因为它不是Map。
您可以使用Jackson annotations来控制类转换为JSON的方式。
例如，这样的事情应该有效：
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.firebase.client.ServerValue;
public class Thing {
private String id;
private Long creationDate;
public Thing() {
}
public Thing(String id) {
this.id = id;
}
public String getId() {
return id;
}
public java.util.Map<String, String> getCreationDate() {
return ServerValue.TIMESTAMP;
}
@JsonIgnore
public Long getCreationDateLong() {
return creationDate;
}
public void setId(String id) {
this.id = id;
}
public void setCreationDate(Long creationDate) {
this.creationDate = creationDate;
}
}
答案 1 :(得分：12)
我知道这个帖子已经过时了，但对于任何尝试实现类似时间戳的人来说，现在可以使用Firebase原生@JsonIgnore而不是使用Jackson注释中的@Exclude。