这是 API 中配置的 JSON 格式:
{
"Hotels":[
{
"EANHotelID":"257219",
"Country":"IN",
"Name":"Toshali Sands Ethnic Village Resort",
"LowRate":"88.32",
"HighRate":"118.77",
"Latitude":"19.83861",
"Longitude":"85.89400",
"Location":"Near the bay",
"PostalCode":"752002",
"PropertyCategory":"3",
"PropertyCurrency":"INR",
"StarRating":"4.0",
"StateProvince":"",
"CheckInTime":"10 AM",
"CheckOutTime":"8 AM",
"City":"Puri",
"Confidence":"52",
"AirportCode":"BBI",
"Caption":"Featured Image",
"ThumbnailURL":"http://media.expedia.com/hotels/2000000/1720000/1710100/1710078/1710078_35_t.jpg",
"URL":"http://media.expedia.com/hotels/2000000/1720000/1710100/1710078/1710078_35_b.jpg"
},
{
"EANHotelID":"397792",
"Country":"IN",
"Name":"MAYFAIR Heritage, Puri",
"LowRate":"138.8325",
"HighRate":"176.55",
"Latitude":"19.79851",
"Longitude":"85.83413",
"Location":"Near Puri Beach",
"PostalCode":"752002",
"PropertyCategory":"1",
"PropertyCurrency":"INR",
"StarRating":"4.0",
"StateProvince":"",
"CheckInTime":"8 AM",
"CheckOutTime":"8 AM",
"City":"Puri",
"Confidence":"60",
"AirportCode":"BBI",
"Caption":"Featured Image",
"ThumbnailURL":"http://media.expedia.com/hotels/5000000/4790000/4780200/4780106/4780106_20_t.jpg",
"URL":"http://media.expedia.com/hotels/5000000/4790000/4780200/4780106/4780106_20_b.jpg"
},
{
"EANHotelID":"397792",
"Country":"IN",
"Name":"MAYFAIR Heritage, Puri",
"LowRate":"138.8325",
"HighRate":"176.55",
"Latitude":"19.79851",
"Longitude":"85.83413",
"Location":"Near Puri Beach",
"PostalCode":"752002",
"PropertyCategory":"1",
"PropertyCurrency":"INR",
"StarRating":"4.0",
"StateProvince":"",
"CheckInTime":"8 AM",
"CheckOutTime":"8 AM",
"City":"Puri",
"Confidence":"60",
"AirportCode":"BBI",
"Caption":"Featured Image",
"ThumbnailURL":"http://media.expedia.com/hotels/5000000/4790000/4780200/4780106/4780106_20_t.jpg",
"URL":"http://media.expedia.com/hotels/5000000/4790000/4780200/4780106/4780106_20_b.jpg"
}
]
}
这些是我使用 GSON 解析 json 的模型类
hotel_list.java
public class hotel_list {
@SerializedName("Hotels")
@Expose
public ArrayList<hotel> hotel_list;
public ArrayList<hotel> getHotel_list() { return hotel_list;}
public void setHotel_list(ArrayList<hotel> hotel_list) {
this.hotel_list = hotel_list;
}
}
酒店.java
public class hotel {
@SerializedName("EANHotelID")
@Expose
private String EANHotelID;
@SerializedName("Country")
@Expose
private String Country;
@SerializedName("Name")
@Expose
private String Name;
@SerializedName("LowRate")
@Expose
private String LowRate;
@SerializedName("HighRate")
@Expose
private String HighRate;
@SerializedName("Latitude")
@Expose
private String Latitude;
@SerializedName("Longitude")
@Expose
private String Longitude;
@SerializedName("Location")
@Expose
private String Location;
@SerializedName("PostalCode")
@Expose
private String PostalCode;
@SerializedName("PropertyCategory")
@Expose
private String PropertyCategory;
@SerializedName("PropertyCurrency")
@Expose
private String PropertyCurrency;
@SerializedName("StarRating")
@Expose
private String StarRating;
@SerializedName("StateProvince")
@Expose
private String StateProvince;
@SerializedName("CheckInTime")
@Expose
private String CheckInTime;
@SerializedName("CheckOutTime")
@Expose
private String CheckOutTime;
@SerializedName("City")
@Expose
private String City;
@SerializedName("Confidence")
@Expose
private String Confidence;
@SerializedName("AirportCode")
@Expose
private String AirportCode;
@SerializedName("Caption")
@Expose
private String Caption;
@SerializedName("ThumbnailURL")
@Expose
private String ThumbnailURL;
@SerializedName("URL")
@Expose
private String URL;
public String getEANHotelID() {
return EANHotelID;
}
public void setEANHotelID(String EANHotelID) {
this.EANHotelID = EANHotelID;
}
public String getCountry() {
return Country;
}
public void setCountry(String country) {
Country = country;
}
public String getName() {
return Name;
}
public void setName(String name) {
Name = name;
}
public String getLowRate() {
return LowRate;
}
public void setLowRate(String lowRate) {
LowRate = lowRate;
}
public String getHighRate() {
return HighRate;
}
public void setHighRate(String highRate) {
HighRate = highRate;
}
public String getLatitude() {
return Latitude;
}
public void setLatitude(String latitude) {
Latitude = latitude;
}
public String getLongitude() {
return Longitude;
}
public void setLongitude(String longitude) {
Longitude = longitude;
}
public String getLocation() {
return Location;
}
public void setLocation(String location) {
Location = location;
}
public String getPostalCode() {
return PostalCode;
}
public void setPostalCode(String postalCode) {
PostalCode = postalCode;
}
public String getPropertyCategory() {
return PropertyCategory;
}
public void setPropertyCategory(String propertyCategory) {
PropertyCategory = propertyCategory;
}
public String getPropertyCurrency() {
return PropertyCurrency;
}
public void setPropertyCurrency(String propertyCurrency) {
PropertyCurrency = propertyCurrency;
}
public String getStarRating() {
return StarRating;
}
public void setStarRating(String starRating) {
StarRating = starRating;
}
public String getStateProvince() {
return StateProvince;
}
public void setStateProvince(String stateProvince) {
StateProvince = stateProvince;
}
public String getCheckInTime() {
return CheckInTime;
}
public void setCheckInTime(String checkInTime) {
CheckInTime = checkInTime;
}
public String getCheckOutTime() {
return CheckOutTime;
}
public void setCheckOutTime(String checkOutTime) {
CheckOutTime = checkOutTime;
}
public String getCity() {
return City;
}
public void setCity(String city) {
City = city;
}
public String getConfidence() {
return Confidence;
}
public void setConfidence(String confidence) {
Confidence = confidence;
}
public String getAirportCode() {
return AirportCode;
}
public void setAirportCode(String airportCode) {
AirportCode = airportCode;
}
public String getCaption() {
return Caption;
}
public void setCaption(String caption) {
Caption = caption;
}
public String getThumbnailURL() {
return ThumbnailURL;
}
public void setThumbnailURL(String thumbnailURL) {
ThumbnailURL = thumbnailURL;
}
public String getURL() {
return URL;
}
public void setURL(String URL) {
this.URL = URL;
}
}
这是 AsyncTask doInBackground 方法，它获取 json 并尝试解析它。
在后台执行
@Override
protected hotel_list doInBackground(Void... params) {
hotel_list hotelList = new hotel_list();
try {
//Create an HTTP client
HttpClient client = new DefaultHttpClient();
HttpGet post = new HttpGet(url);
//Perform the request and check the status code
HttpResponse response = client.execute(post);
StatusLine statusLine = response.getStatusLine();
Log.e(REST, Integer.toString(statusLine.getStatusCode()));
if (statusLine.getStatusCode() == 200) {
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
try {
//Read the server response and attempt to parse it as JSON
BufferedReader reader = new BufferedReader(new InputStreamReader(content));
// Log.e(TAG, reader.readLine());
GsonBuilder gsonBuilder = new GsonBuilder();
gsonBuilder.setDateFormat("M/d/yy hh:mm a");
Gson gson = gsonBuilder.create();
String str=reader.readLine();
Log.i("json object",str);
hotelList = gson.fromJson(reader, hotel_list.class);
content.close();
// handlePostsList(posts);
} catch (Exception ex) {
Log.e(REST, "Failed to parse JSON due to: " + ex);
}
} else {
Log.e(REST, "Server responded with status code: " + statusLine.getStatusCode());
}
} catch (Exception ex) {
Log.e(REST, "Failed to send HTTP POST request due to: " + ex);
}
Log.i("list",hotelList.getHotel_list().get(1).getName());
return hotelList;
}
现在的问题是返回的 hotelList 为 null。 GSON 没有显示任何错误，但解析的内容没有填充到列表中，并且它仍然是空的。我究竟做错了什么？
Logcat 消息 -
09-23 01:42:52.374 1950-1963/com.neelraj.hotels W/art﹕ Suspending all threads took: 25.899ms
09-23 01:42:54.321 1950-1995/com.neelraj.hotels I/json object﹕ " {\"Hotels\":[{\"EANHotelID\":\"176933\",\"Country\":\"IN\",\"Name\":\"The Park Kolkata\",\"LowRate\":\"76.13\",\"HighRate\":\"226.5\",\"Latitude\":\"22.55409\",\"Longitude\":\"88.35143\",\"Location\":\"Near New Market\",\"PostalCode\":\"700016\",\"PropertyCategory\":\"1\",\"PropertyCurrency\":\"INR\",\"StarRating\":\"5.0\",\"StateProvince\":\"\",\"CheckInTime\":\"2 PM\",\"CheckOutTime\":\"noon\",\"City\":\"Kolkata\",\"Confidence\":\"52\",\"AirportCode\":\"CCU\",\"Caption\":\"Featured Image\",\"ThumbnailURL\":\"http://media.expedia.com/hotels/1000000/530000/523000/522928/522928_33_t.jpg\",\"URL\":\"http://media.expedia.com/hotels/1000000/530000/523000/522928/522928_33_b.jpg\"},{\"EANHotelID\":\"185519\",\"Country\":\"IN\",\"Name\":\"The Peerless Inn - Kolkata\",\"LowRate\":\"91.36\",\"HighRate\":\"137.04\",\"Latitude\":\"22.56217\",\"Longitude\":\"88.35157\",\"Location\":\"Near New Market\",\"PostalCode\":\"700 013\",\"PropertyCategory\":\"1\",\"PropertyCurrency\":\"INR\",\"StarRating\":\"4.0\",\"StateProvince\":\"\",\"CheckInTime\":\"noon\",\"CheckOutTime\":\"noon\",\"City\":\"Kolkata\",\"Confidence\":\"52\",\"AirportCode\":\"CCU\",\"Caption\":\"Featured Image\",\"ThumbnailURL\":\"http://media.expedia.com/hotels/2000000/1070000/1066400/1066383/1066383_13_t.jpg\",\"URL\":\"http://media.expedia.com/hotels/2000000/1070000/1066400/1066383/1066383_13_b.jpg\"},{\"EANHotelID\":\"516167\",\"Country\":\"IN\",\"Name\":\"Hotel O2 VIP\",\"LowRate\":\"56.32\",\"HighRate\":\"71.55\",\"Latitude\":\"22.63360\",\"Longitude\":\"88.43468\",\"Location\":\"In Kolkata (Dum Dum)\",\"PostalCode\":\"700052\",\"PropertyCategory\":\"1\",\"PropertyCurrency\":\"INR\",\"StarRating\":\"3.0\",\"StateProvince\":\"\",\"CheckInTime\":\"\",\"CheckOutTime\":\"noon\",\"City\":\"kolkata\",\"Confidence\":\"\",\"AirportCode\":\"CCU\",\"Caption\":\"Featured Image\",\"ThumbnailURL\":\"http://media.expedia.com/hotels/12000000/11040000/11032100/11032008/11032008_3_t.jpg\",\"URL\":\"http://media.expedia.com/hotels/12000000/11040000/11032100/11032008/11032008_3_b.jpg\"},{\"EANHotelID\":\"198401\",\"Country\":\"IN\",\"Name\":\"Taj Bengal\",\"LowRate\":\"192.7119\",\"HighRate\":\"859.6464\",\"Latitude\":\"22.53706\",\"Longitude\":\"88.33366\",\"Location\":\"Near Alipore Zoo\",\"PostalCode\":\"700 027\",\"PropertyCategory\":\"1\",\"PropertyCurrency\":\"INR\",\"StarRating\":\"5.0\",\"StateProvince\":\"\",\"CheckInTime\":\"2 PM\",\"CheckOutTime\":\"Noon\",\"City\":\"Kolkata\",\"Confidence\":\"95\",\"AirportCode\":\"CCU\",\"Caption\":\"Featured Image\",\"ThumbnailURL\":\"http://media.expedia.com/hotels/1000000/470000/465100/465007/465007_77_t.jpg\",\"URL\":\"http://media.expedia.com/hotels/1000000/470000/465100/465007/465007_77_b.jpg\"},{\"EANHotelID\":\"215054\",\"Country\":\"IN\",\"Name\":\"ITC Sonar Kolkata\",\"LowRate\":\"174.9995\",\"HighRate\":\"221.9965\",\"Latitude\":\"22.54331\",\"Longitude\":\"88.39665\",\"Location\":\"Near Science City\",\"PostalCode\":\"700046\",\"PropertyCategory\":\"1\",\"PropertyCurrency\":\"INR\",\"StarRating\":\"5.0\",\"StateProvince\":\"\",\"CheckInTime\":\"2 PM\",\"CheckOutTime\":\"\",\"City\":\"Kolkata\",\"Confidence\":\"52\",\"AirportCode\":\"CCU\",\"Caption\":\"Featured Image\",\"ThumbnailURL\":\"http://media.expedia.com/hotels/1000000/930000/922100/922011/922011_66_t.jpg\",\"URL\":\"http://media.expedia.com/hotels/1000000/930000/922100/922011/922011_66_b.jpg\"},{\"EANHotelID\":\"219474\",\"Country\":\"IN\",\"Name\":\"Golden Parkk\",\"LowRate\":\"78.57\",\"HighRate\":\"126.9\",\"Latitude\":\"22.54741\",\"Longitude\":\"88.34966\",\"Location\":\"Near Victoria Memorial\",\"PostalCode\":\"700071\",\"PropertyCategory\":\"1\",\"PropertyCurrency\":\"INR\",\"StarRating\":\"3.0\",\"StateProvince\":\"\",\"CheckInTime\":\"3 PM\",\"CheckOutTime\":\"noon\",\"City\":\"Kolkata\",\"Confidence\":\"52\",\"AirportCode\":\"CCU\",\"Caption\":\"Featured Image\",\"ThumbnailURL\":\"http://media.expedia.com/hotels/2000000/1060000/1056000/1055970/1055970_41_t.jpg\",\"URL\":\"http://media.expedia.com/hotels/2000000/1060000/105
09-23 01:42:54.344 1950-1995/com.neelraj.hotels E/AndroidRuntime﹕ FATAL EXCEPTION: AsyncTask #1
Process: com.neelraj.hotels, PID: 1950
java.lang.RuntimeException: An error occured while executing doInBackground()
at android.os.AsyncTask$3.done(AsyncTask.java:300)
at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
at java.util.concurrent.FutureTask.run(FutureTask.java:242)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
at java.lang.Thread.run(Thread.java:818)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'java.util.ArrayList com.neelraj.hotels.model.hotel_list.getHotel_list()' on a null object reference
at com.neelraj.hotels.MainActivity$Fetch.doInBackground(MainActivity.java:153)
at com.neelraj.hotels.MainActivity$Fetch.doInBackground(MainActivity.java:84)
at android.os.AsyncTask$2.call(AsyncTask.java:288)
at java.util.concurrent.FutureTask.run(FutureTask.java:237)
at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
最佳答案
尝试将通用列表类型更改为简单数组:
public ArrayList<hotel> hotel_list;
至:
public hotel[] hotel_list;
和
Gson gson = gsonBuilder.create();
至:
Gson gson = new Gson();
关于java - Gson解析问题，空指针异常，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/32725464/