我正在尝试在firebase数据库的以下层次结构中获取每个节点及其子节点的值。因此，我已经建立了以下对象模型作为 First Approch ：
public class FirebaseTripDataHolder {
String currentStatus,distanceLengthStr, driverId, durationStr, fareEstimate ;
public FirebaseTripDataHolder() {
}
public FirebaseTripDataHolder(String key, String tripStatus, String distanceSTR, String driverIDStr, String durationStr, String fareEstimate) {
currentStatus=tripStatus;
distanceLengthStr=distanceSTR;
driverId=driverIDStr;
this.durationStr=durationStr;
this.fareEstimate=fareEstimate;
}
public String getCurrentStatus() {
return currentStatus;
}
public void setCurrentStatus(String currentStatus) {
this.currentStatus = currentStatus;
}
public String getDistanceLengthStr() {
return distanceLengthStr;
}
public void setDistanceLengthStr(String distanceLengthStr) {
this.distanceLengthStr = distanceLengthStr;
}
public String getDriverId() {
return driverId;
}
public void setDriverId(String driverId) {
this.driverId = driverId;
}
public String getDurationStr() {
return durationStr;
}
public void setDurationStr(String durationStr) {
this.durationStr = durationStr;
}
public String getFareEstimate() {
return fareEstimate;
}
public void setFareEstimate(String fareEstimate) {
this.fareEstimate = fareEstimate;
}
}
然后，我创建了一个for循环来获取DataSnapshot的子级，如以下代码片段所示：
for (DataSnapshot ds : dataSnapshot.getChildren()) {
FirebaseTripDataHolder tripDataHolder= ds.getValue(FirebaseTripDataHolder.class);
TripStatus= tripDataHolder.getCurrentStatus();
DistanceSTR=tripDataHolder.getDistanceLengthStr();
DriverIDStr=tripDataHolder.getDriverId();
DurationStr=tripDataHolder.getDurationStr();
FareEstimate=tripDataHolder.getFareEstimate();
}
但是，以下行已返回异常
com.google.firebase.database.DatabaseException：无法将类型为java.lang.String的对象转换为models.firebase.FirebaseTripDataHolder
我试图对stackoverflow进行一些研究，但遇到了很多解决方案，例如 Alex Mamo的答案here，它看起来是一个问题，我尝试了他的两个解决方案并使用了也是即将采用的第二种方法：
for (DataSnapshot ds : dataSnapshot.getChildren()) {
KEY = ds.getKey();
TripStatus = ds.child("currentStatus").getValue(String.class);
DistanceSTR = ds.child("distanceLengthStr").getValue(String.class);
DriverIDStr = ds.child("driverId").getValue(String.class);
DurationStr = ds.child("durationStr").getValue(String.class);
FareEstimate = ds.child("fareEstimate").getValue(String.class);
}
但是，在第二种方法中，OnDataChange方法中的dataSnapShot看起来有数据，但是文件针对每个属性返回空值。 另外，我不知道如何完成我的对象来检索主DataSnapShot的子节点，例如： 下图中的 * customerCoordinates，customerInfo，distinationCoordinates * ： enter image description here
任何人都可以在这个问题上提供帮助。谢谢
更新一个（1） 有关更多说明，这是我的json格式，来自DataSnapShot键中的firebase：
DataSnapshot { key = -Lv-5lEphq-F4TL1Q2_e, value = {distanceLength=12, customerCoordinates={address=Unnamed Road, lat=29.9774451, lng=31.2082394}, driverCoordinates={lat=29.977426, lng=31.212798}, fareEstimate=72, driverInfo={rate=5, name=driver29, deviceId=dYB0RihjjxY:APA91bFluyZ6iS0YDNKyY72TJl4Y9tx52MrVSwGKQkwJDuS9SVJ6XBlkpfCK1_bIIv675mY72cEr2en31qBPBzMOyaSE-zQHPBQJqdTDdkx-BZSyHZAeK5L1RBBrQRBuXPRsWiuJL2-h, mobile=01478529637}, durationStr=34 mins, distinationCoordinates={address=5 ش Ahmed Al Hasawi, lat=29.980184747972555, lng=31.25940430909395}, vehicleInfo={colorNames={ar=ازرق, en=Blue}, brandNames={ar=قيات, en=Fiat}, rideCategoryNames={ar=اقتصادي, en=Economy}, plateNo=789654, categoryNames={ar=تيبو, en=Tipo}, colorCode=#0000ff, typeNames={ar=موتوسكل, en=Bikes}}, currentStatus=Accept, customerInfo={name=mohamed, deviceId=eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IkNVMTIxNjc4NzU2ODc3IiwiZW1haWwiOiJwcm9vZmVzc2VyQGdtYWlsLmNvbSIsInR5cGUiOiJDdXN0b21lciIsImlhdCI6MTU3NDEwMjE4MywiZXhwIjoxNTc2Njk0MTgzfQ.jqHNFmbLmOgS81y_vmpkVscsTDCrxBQiwfQPXuZLWTA, mobile=1097555350221}, driverId=DR472264941939, duration=34, distanceLengthStr=12.4 km} }
更新两（2）
当datasnapshot看起来像DataSnapshot { key = currentStatus, value = Accept }那样的for循环时：
for (DataSnapshot ds : dataSnapshot.getChildren()) {
TripStatus = ds.child("currentStatus").getValue(String.class);
}
TripStatus等于null
更新三（3）
我的Firebase数据库参考是： tripsReference = FirebaseDatabase.getInstance（“ https://wasalny-6139e.firebaseio.com/”）。getReference（）。child（“ trips”）。child（firebaseListenedTripID）;我问我的对象是否合适，我需要捕获行程节点中的每个节点和子节点值，就像我想获取客户坐标，客户信息和destinationCoordinates
更新四（4） 我的firebaseDatabase json格式，而不是附加的图像：
{
"drivers" : {
"DR117419391945" : {
".priority" : "stq6f8rfgx",
"g" : "stq6f8rfgx",
"l" : [ 30.0165321, 31.4097233 ]
},
"DR472264941939" : {
".priority" : "stq6fb27s5",
"g" : "stq6fb27s5",
"l" : [ 30.0166408, 31.4104284 ]
}
},
"trips" : {
"-Lv-BYEQPVDSV_AYAjPo" : {
"currentStatus" : "Accept",
"customerCoordinates" : {
"address" : "Unnamed Road",
"lat" : 29.9774637,
"lng" : 31.2082546
},
"customerInfo" : {
"deviceId" : "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IkNVMTIxNjc4NzU2ODc3IiwiZW1haWwiOiJwcm9vZmVzc2VyQGdtYWlsLmNvbSIsInR5cGUiOiJDdXN0b21lciIsImlhdCI6MTU3NDEwMjE4MywiZXhwIjoxNTc2Njk0MTgzfQ.jqHNFmbLmOgS81y_vmpkVscsTDCrxBQiwfQPXuZLWTA",
"mobile" : "1097555350221",
"name" : "mohamed"
},
"distanceLength" : 12,
"distanceLengthStr" : "12.4 km",
"distinationCoordinates" : {
"address" : "5 ش Ahmed Al Hasawi",
"lat" : 29.980184747972555,
"lng" : 31.25940430909395
},
"driverCoordinates" : {
"lat" : 29.977426,
"lng" : 31.212798
},
"driverId" : "DR472264941939",
"driverInfo" : {
"deviceId" : "dYB0RihjjxY:APA91bFluyZ6iS0YDNKyY72TJl4Y9tx52MrVSwGKQkwJDuS9SVJ6XBlkpfCK1_bIIv675mY72cEr2en31qBPBzMOyaSE-zQHPBQJqdTDdkx-BZSyHZAeK5L1RBBrQRBuXPRsWiuJL2-h",
"mobile" : "01478529637",
"name" : "driver29",
"rate" : 5
},
"duration" : 34,
"durationStr" : "34 mins",
"fareEstimate" : 72,
"vehicleInfo" : {
"brandNames" : {
"ar" : "قيات",
"en" : "Fiat"
},
"categoryNames" : {
"ar" : "تيبو",
"en" : "Tipo"
},
"colorCode" : "#0000ff",
"colorNames" : {
"ar" : "ازرق",
"en" : "Blue"
},
"plateNo" : "789654",
"rideCategoryNames" : {
"ar" : "اقتصادي",
"en" : "Economy"
},
"typeNames" : {
"ar" : "موتوسكل",
"en" : "Bikes"
}
}
}
}
}
更新五（5） 我已经在dataSnapShot对象中获取了所有Trips节点及其子节点，问题是如何将其解析为FirebaseTripDataHolder对象！？
答案 0 :(得分：0)
找不到您的query至FirebaseDatabase。尝试使用以下代码：
FirebaseDatabase database = FirebaseDatabase.getInstance();
database.getReference().child("trips").addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
for(DataSnapshot childSnapshot: dataSnapshot.getChildren()) {
FirebaseTripDataHolder tripDataHolder = childSnapshot.getValue(FirebaseTripDataHolder.class);
String TripStatus= tripDataHolder.getCurrentStatus();
String DistanceSTR=tripDataHolder.getDistanceLengthStr();
String DriverIDStr=tripDataHolder.getDriverId();
String DurationStr=tripDataHolder.getDurationStr();
long FareEstimate=tripDataHolder.getFareEstimate();
}
}
@Override
public void onCancelled(@NonNull DatabaseError databaseError) {
}
});
FirebaseTripDataHolder.java
public class FirebaseTripDataHolder {
String currentStatus,distanceLengthStr, driverId, durationStr;
long fareEstimate;
public FirebaseTripDataHolder() {
}
public FirebaseTripDataHolder(String key, String tripStatus, String distanceSTR, String driverIDStr, String durationStr, long fareEstimate) {
currentStatus=tripStatus;
distanceLengthStr=distanceSTR;
driverId=driverIDStr;
this.durationStr=durationStr;
this.fareEstimate=fareEstimate;
}
public String getCurrentStatus() {
return currentStatus;
}
public void setCurrentStatus(String currentStatus) {
this.currentStatus = currentStatus;
}
public String getDistanceLengthStr() {
return distanceLengthStr;
}
public void setDistanceLengthStr(String distanceLengthStr) {
this.distanceLengthStr = distanceLengthStr;
}
public String getDriverId() {
return driverId;
}
public void setDriverId(String driverId) {
this.driverId = driverId;
}
public String getDurationStr() {
return durationStr;
}
public void setDurationStr(String durationStr) {
this.durationStr = durationStr;
}
public long getFareEstimate() {
return fareEstimate;
}
public void setFareEstimate(long fareEstimate) {
this.fareEstimate = fareEstimate;
}
}