com.google.gson.JsonSyntaxException：java.lang.IllegalStateException：预期为 BEGIN_OBJECT，但在第 1 行第 2 列是 BEGIN_ARRAY
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com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2
提问by hesham
i wanna to pass List of Student as List from AsyncTask to Activity using Gson library
我想使用 Gson 库将学生列表作为列表从 AsyncTask 传递到 Activity
But it gives me the following error :
但它给了我以下错误：
ERROR LOG :
错误日志：
FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.hesham.sams/com.hesham.sams.ListActivity1}: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2110)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2135)
at android.app.ActivityThread.access0(ActivityThread.java:140)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1237)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4921)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1038)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:805)
at dalvik.system.NativeStart.main(Native Method)
Caused by: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:176)
at com.google.gson.Gson.fromJson(Gson.java:803)
at com.google.gson.Gson.fromJson(Gson.java:768)
at com.google.gson.Gson.fromJson(Gson.java:717)
at com.google.gson.Gson.fromJson(Gson.java:689)
at com.hesham.sams.ListActivity1.getNames(ListActivity1.java:171)
at com.hesham.sams.ListActivity1.onCreate(ListActivity1.java:68)
at android.app.Activity.performCreate(Activity.java:5206)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1094)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2074)
... 11 more
Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2
at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:374)
at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:165)
... 20 more
My AsyncTask Full class :
我的 AsyncTask 完整课程：
public class GetListAsync extends AsyncTask<Void, Void, ArrayList<Student>> {
private Activity activity;
private ProgressDialog progressDialog;
Context context;
public GetListAsync(Activity activity, ProgressDialog progressDialog, Context context) {
super();
this.progressDialog = progressDialog;
this.activity = activity;
this.context = context;
}
private Student get(String s) {
return new Student(s);
}
@Override
protected ArrayList<Student> doInBackground(Void... voids) {
ArrayList<Student> StudentIdList = new ArrayList<Student>();
ArrayList<Student> StudentNamesList = new ArrayList<Student>();
SharedPreferences prefs = PreferenceManager
.getDefaultSharedPreferences(context);
String TID = prefs.getString("TID", null);
SoapObject request2 = new SoapObject(NAMESPACE2, METHOD_NAME2);
PropertyInfo pi2 = new PropertyInfo();
pi2.setName("TID");
pi2.setValue(Integer.parseInt(TID.toString()));
pi2.setType(Integer.class);
request2.addProperty(pi2);
SoapSerializationEnvelope envelope2 = new SoapSerializationEnvelope(
SoapEnvelope.VER11);
envelope2.setOutputSoapObject(request2);
HttpTransportSE androidHttpTransport2 = new HttpTransportSE(URL2);
try {
androidHttpTransport2.call(SOAP_ACTION2, envelope2);
KvmSerializable result = (KvmSerializable) envelope2.bodyIn;
String str = null;
for (int i = 0; i < result.getPropertyCount(); i++) {
str = ((String) result.getProperty(i).toString());
StudentIdList.add(get(str));
}
return StudentIdList;
} catch (Exception e) {
}
return StudentIdList;
}
@Override
protected void onPostExecute(ArrayList<Student> result) {
GsonBuilder gsonb = new GsonBuilder();
Gson gson = gsonb.create();
String json = gson.toJson(result);
SharedPreferences prefs = PreferenceManager
.getDefaultSharedPreferences(context);
prefs.edit().putString("studentnames", json).commit();
activity.startActivity(new Intent(activity, ListActivity1.class));
progressDialog.dismiss();
}
}
Here is ListView1 Activity method that's should return or get that list from AsyncTask: Note : I think the error cused from here in comment
这是应该从 AsyncTask 返回或获取该列表的 ListView1 Activity 方法： 注意：我认为这里在评论中引用了错误
public List<Student> getNames() {
SharedPreferences prefs = PreferenceManager
.getDefaultSharedPreferences(getApplicationContext());
Gson gson = new Gson();
String result = prefs.getString("studentnames", null);
Student obj = gson.fromJson(result, Student.class); // MayBe the error here in class type
Toast.makeText(getApplicationContext(), obj.toString(),
Toast.LENGTH_LONG).show();
return (List<Student>) obj;
}
I need you help cuz it's first time to use Gson Library .
我需要你的帮助，因为这是第一次使用 Gson 库。
回答by giampaolo
You serialized a listof Studentinstances but you try to deserialize a single Studentfrom your saved string. Try this instead:
您序列化了一个实例列表，Student但您尝试Student从保存的字符串中反序列化一个。试试这个：
Gson gson = new Gson();
String result = prefs.getString("studentnames", null);
ArrayList<Student> list = new ArrayList<Student>();
Type listType = new TypeToken<List<Student>>() {}.getType();
list = gson.fromJson(result, listType);
回答by TanvirChowdhury
This may help.Instead of deserializing a single student object try this.
这可能会有所帮助。而不是反序列化单个学生对象试试这个。
List<Student> expectedList = new Gson()
.fromJson(prefs.getString("studentnames", null),
new TypeToken<List<Student>>() {}.getType());
