java - 从火力地堡检索数据

Question

每次执行时我都会收到下面的堆栈跟踪错误

GenericTypeIndicator<List<String>> t = new GenericTypeIndicator<List<String>>() {
         };
         GenericTypeIndicator<List<String>> t2 = new GenericTypeIndicator<List<String>>() {};
         List<String>  namelist =  snapshot.child("Driver name").getValue(t);
         List<String> carlist =  snapshot.child("Drivers car").getValue(t2);
         if (namelist!=null & carlist!=null){


         for(int wee=0;wee<namelist.size();wee++){
             driver.add(new Driver(namelist.get(wee).toString(),carlist.get(wee).toString()));
         }

我发送到 firebase 的数据存储为:

"DriversList" : {
    "Driver name" : {
      "-Js6OJniEqVZAYSNhqbB" : "gvvb",
      "-Js7GjPMGNOLurrKk9rC" : "iggvv",
      "-Js7GlUlCwIoljJxpFbZ" : "iiggv",
      "-Js7GnBCRogiFUfn-ncZ" : "ihccvv",
      "-Js7GqGxH2vLYK5tsjjP" : "hhvv",
      "-Js7Gs80AoB5eeWci6jW" : "hhgc",
      "-Js7Gtm6AGh_QaTUK6fQ" : "ugghh",
      "-Js7GyomOIzjtVo3-PVg" : "tyygff",
      "-JsPxEhf4tx7O4v7JWMc" : "",
      "-JsQBoMqVBF4SzOHF3WA" : "rr",
      "-JsQC6TuGqHrBBkdalik" : "eed"
    },
    "Drivers availability" : {
      "-Js6OJozSuUvj5JnuNnW" : "No",
      "-Js7GjQ_5YgmnEYKWHrL" : "No",
      "-Js7GlVm7onoQd59Yyfq" : "No",
      "-Js7GnDPdjseoRVjgwSn" : "No",
      "-Js7GqIYy4VSEqu9qZfC" : "No",
      "-Js7Gs8VP5mp5bOR1pxR" : "No",
      "-Js7Gtmfv2M2p201k3Ra" : "No",
      "-Js7Gyvf8JkGwBlh8ZLu" : "No",
      "-JsPxEly9iGncA4VWvn2" : "No",
      "-JsQBoOE6AbGy1VMBSWp" : "No",
      "-JsQC6wGzBXBMz76IXue" : "No"
    },
    "Drivers car" : {
      "-Js6OJoyDlc4DR0IQhJr" : "gvgh",
      "-Js7GjQZ6Sb7AOooABt3" : "nbcgg",
      "-Js7GlVajAA1B5PeBnn2" : "nvvuuu",
      "-Js7GnDOCiWM874f6iL6" : "",
      "-Js7GqIYy4VSEqu9qZfB" : "nbcxx",
      "-Js7Gs8VP5mp5bOR1pxQ" : "hbccf",
      "-Js7Gtmfv2M2p201k3R_" : "hvccf",
      "-Js7Gyvf8JkGwBlh8ZLt" : "gghhhg",
      "-JsPxElx9XXm0kVLFstN" : "",
      "-JsQBoOE6AbGy1VMBSWo" : "dd",
      "-JsQC6wF0zgLApv8SwJO" : "ff"
    }

堆栈跟踪错误:

06-30 14:35:44.918    2736-2736/com.kate.teme E/AndroidRuntime﹕ FATAL EXCEPTION: main
    com.firebase.client.FirebaseException: Failed to bounce to type
            at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:208)
            at com.kate.teme.AdminContent$2.onDataChange(AdminContent.java:105)
            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$1.run(EventRaiser.java:38)
            at android.os.Handler.handleCallback(Handler.java:800)
            at android.os.Handler.dispatchMessage(Handler.java:100)
            at android.os.Looper.loop(Looper.java:194)
            at android.app.ActivityThread.main(ActivityThread.java:5371)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: com.shaded.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.ArrayList out of START_OBJECT token
            at [Source: java.io.StringReader@42af1900; line: 1, column: 1]
            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.StringCollectionDeserializer.handleNonArray(StringCollectionDeserializer.java:218)
            at com.shaded.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:166)
            at com.shaded.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:156)
            at com.shaded.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:19)
            at com.shaded.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:2888)
            at com.shaded.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2041)
            at com.firebase.client.DataSnapshot.getValue(DataSnapshot.java:206)
            at com.kate.teme.AdminContent$2.onDataChange(AdminContent.java:105)
            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$1.run(EventRaiser.java:38)
            at android.os.Handler.handleCallback(Handler.java:800)
            at android.os.Handler.dispatchMessage(Handler.java:100)
            at android.os.Looper.loop(Looper.java:194)
            at android.app.ActivityThread.main(ActivityThread.java:5371)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:525)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

查看您的数据结构:

"Driver name" : {
  "-Js6OJniEqVZAYSNhqbB" : "gvvb",
  "-Js7GjPMGNOLurrKk9rC" : "iggvv",
  "-Js7GlUlCwIoljJxpFbZ" : "iiggv",
  "-Js7GnBCRogiFUfn-ncZ" : "ihccvv",
  "-Js7GqGxH2vLYK5tsjjP" : "hhvv",
  "-Js7Gs80AoB5eeWci6jW" : "hhgc",
  "-Js7Gtm6AGh_QaTUK6fQ" : "ugghh",
  "-Js7GyomOIzjtVo3-PVg" : "tyygff",
  "-JsPxEhf4tx7O4v7JWMc" : "",
  "-JsQBoMqVBF4SzOHF3WA" : "rr",
  "-JsQC6TuGqHrBBkdalik" : "eed"
}

您尝试将其反序列化为 List<String> .但它实际上是一个 Map<String,String> .所以:

@Override
public void onDataChange(DataSnapshot snapshot) {
    GenericTypeIndicator<Map<String,String>> mapType = new GenericTypeIndicator<Map<String, String>>() { };
    Map<String,String>  namelist =  snapshot.child("Driver name").getValue(mapType);
    Map<String,String> carlist =  snapshot.child("Drivers car").getValue(mapType);
    if (namelist!=null & carlist!=null) {
        for (String name: namelist.values()) {
            System.out.println(name);
        }
    }
}

请注意，我不知道您是如何匹配司机和他们的汽车的。我强烈建议您在继续编码之前重新考虑这个数据结构。

一种可能的结构:

"DriversList": {
  "-Js6OJniEqVZAYSNhqbB" : {
    "name": "puf",
    "available": false,
    "car": "Toyota RAV4"
  },
  "-Js7GjPMGNOLurrKk9rC" : {
    "name": "manon",
    "available": false,
    "car": "Toyota Matrix"
  },
  ...
}

要读/写这些，你需要一个 Driver类:

public class Driver {
  String name;
  Boolean available;
  String car;

  public Driver() {}

  public String getName() { return name; }
  public Boolean getAvailable() { return available; }
  public String getCar() { return car; }
}

然后:

public void onDataChange(DataSnapshot snapshot) {
    GenericTypeIndicator<Map<String,Driver>> mapType = new GenericTypeIndicator<Map<String, Driver>>() { };
    Map<String,Driver> drivers = snapshot.getValue(mapType);
    if (drivers!=null) {
        for (Driver driver: drivers.values()) {
            System.out.println(driver.name);
        }
    }
}