我正在调用一个Web服务，该服务从数据库中获取数据并输出以下JSON：
{"eventId":"1","eventTitle":"opening ceremony","eventCategory":"store","eventSubCategory":"clothing","eventDescription":"This is an event description of some kid for the first event","eventDate":"13/05/2012","eventTime":"14:52","eventAddress":"49 somerset road","eventCity":"southsea","eventCountry":"UK","eventWebsite":"www.nxtldn.com","eventEmail":"lg@nxtldn.com","eventPhone":"07757491567","eventKeywords":"clothes, street, wear, heart, love"},{"eventId":"2","eventTitle":"cupcakes","eventCategory":"Store","eventSubCategory":"food","eventDescription":"This is an event description of some kid for the second event","eventDate":"17/05/2012","eventTime":"11:22","eventAddress":"12 cleveleys road","eventCity":"london","eventCountry":"UK","eventWebsite":"www.ashshort.com","eventEmail":"ashshort@short.com","eventPhone":"0778514562","eventKeywords":"cupcakes, store, london, hipster"}]
我附加（我已经使用 http://jsonlint.com/测试了 JSON 是否有效）：
{"Events":[{"eventId":"1","eventTitle":"opening ceremony","eventCategory":"store","eventSubCategory":"clothing","eventDescription":"This is an event description of some kid for the first event","eventDate":"13/05/2012","eventTime":"14:52","eventAddress":"49 somerset road","eventCity":"southsea","eventCountry":"UK","eventWebsite":"www.nxtldn.com","eventEmail":"lg@nxtldn.com","eventPhone":"07757491567","eventKeywords":"clothes, street, wear, heart, love"},{"eventId":"2","eventTitle":"cupcakes","eventCategory":"Store","eventSubCategory":"food","eventDescription":"This is an event description of some kid for the second event","eventDate":"17/05/2012","eventTime":"11:22","eventAddress":"12 cleveleys road","eventCity":"london","eventCountry":"UK","eventWebsite":"www.ashshort.com","eventEmail":"ashshort@short.com","eventPhone":"0778514562","eventKeywords":"cupcakes, store, london, hipster"}]}
我正在使用AsyncTask调用它
public class EventSync extends AsyncTask<String, Integer, EventsList> {
EventsList elist1 = new EventsList();
@Override
protected EventsList doInBackground(String... urls) {
String tempurl = urls[0];
String output = "";
InputStream is = null;
StringBuilder sb = new StringBuilder();
EventsList list = new EventsList();
try
{
URL url = new URL(tempurl);
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.connect();
is = con.getInputStream();
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
String line = null;
while((line = reader.readLine()) != null)
{
sb.append(line + "n");
}
}
catch (Exception e)
{
e.printStackTrace();
}
finally
{
try
{
is.close();
}
catch (IOException e)
{
e.printStackTrace();
}
}
output = sb.toString();
String json = "{"Events":" + output + "}";
System.out.println(json);
Gson gson = new Gson();
// When debugging this is the line I believe it fails on, It points to a bit of memory but the list is empty.
EventsList jsonlist = gson.fromJson(json, EventsList.class);
return jsonlist;
}
@Override
protected void onPostExecute(EventsList list)
{
System.out.println("in on post");
for (Event event : list.getEvents())
{
System.out.println(event.getEventId());
}
}}
public class EventsList {
public EventsList(){
}
private List<Event> events;
public List<Event> getEvents()
{
return events;
}
public void setEventsList(List<Event> events)
{
this.events = events;
}}
public class Event {
private String eventId;
private String eventTitle;
private String eventCategory;
private String eventSubCategory;
private String eventDescription;
private String eventDate;
private String eventTime;
private String eventAddress;
private String eventCity;
private String eventCountry;
private String eventWebsite;
private String eventEmail;
private String eventPhone;
private String eventKeywords;
public Event()
{
}
// ALL GETS AND SETS
目前，我只是尝试测试它，看看它是否会在使用自定义适配器填充列表视图之前返回。但不幸的是，我收到以下错误：
11-10 23:37:08.315: E/AndroidRuntime(5592): FATAL EXCEPTION: main
11-10 23:37:08.315: E/AndroidRuntime(5592): java.lang.NullPointerException
11-10 23:37:08.315: E/AndroidRuntime(5592): at com.nxtldn.trill.EventSync.onPostExecute(EventSync.java:71)
11-10 23:37:08.315: E/AndroidRuntime(5592): at com.nxtldn.trill.EventSync.onPostExecute(EventSync.java:1)
11-10 23:37:08.315: E/AndroidRuntime(5592): at android.os.AsyncTask.finish(AsyncTask.java:631)
11-10 23:37:08.315: E/AndroidRuntime(5592): at android.os.AsyncTask.access$600(AsyncTask.java:177)
11-10 23:37:08.315: E/AndroidRuntime(5592): at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
11-10 23:37:08.315: E/AndroidRuntime(5592): at android.os.Handler.dispatchMessage(Handler.java:99)
11-10 23:37:08.315: E/AndroidRuntime(5592): at android.os.Looper.loop(Looper.java:137)
11-10 23:37:08.315: E/AndroidRuntime(5592): at android.app.ActivityThread.main(ActivityThread.java:4745)
11-10 23:37:08.315: E/AndroidRuntime(5592): at java.lang.reflect.Method.invokeNative(Native Method)
11-10 23:37:08.315: E/AndroidRuntime(5592): at java.lang.reflect.Method.invoke(Method.java:511)
11-10 23:37:08.315: E/AndroidRuntime(5592): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
11-10 23:37:08.315: E/AndroidRuntime(5592): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
11-10 23:37:08.315: E/AndroidRuntime(5592): at dalvik.system.NativeStart.main(Native Method)
我是Android的新手，所以我不确定是否有更好的方法或正确的方法是什么。
我的 JSON 结构是否取决于 GSON 不接受并返回空指针？
提前非常感谢任何可以帮助:)的人
尝试更改
EventsList jsonlist = gson.fromJson(json, EventsList.class);
自
Event[] jsonlist = gson.fromJson(json, Event[].class);
这是假设您在 Web 服务中使用了 Event 类型的数组（如上例所示）来创建此 json。我认为当前的问题是您的 json 字符串与类 EventList 不匹配，因此返回 null。确保服务和安卓项目中的事件类匹配。
在事件列表中，您期望事件列表（集合），但您附加的 JSON 实际上是一个对象："{\"事件"：" + 输出 + "}";也许您希望它看起来像这样：
"{"Events":[" + output + "]}";
这会将您的单个事件放入一系列潜在事件中。您的用例令人困惑，我不确定为什么要将单个 JSON 对象放入数组中，但也许我缺少更多详细信息。
我发现这是因为我将"/n"添加到我的字符串生成器中，创建新行并切断了 json 的最后一个 }。谢谢大家