预计BEGIN_ARRAY但在第1行第2列是BEGIN_OBJECT .....在Android中尝试使用GSON解析JSON时出错？

Question

我是android的新手.这是JSONString我已经存储在我的项目中.

public class MainActivity extends Activity {
    MenuFields menuFieldInstance[];

    Gson gson = new Gson();

    String jsonObjectString = "{\n\n\n [\n \"id\": 22,\n \"menu_id\": 1,\n \"field_type_id\": 1,\n \"c4w_code\": \"1234\",\n \"field_label\": \"Customer No\",\n \"field_values\": \"\",\n \"date_Created\": \"2012-09-16 05:11:23\",\n \"date_modified\": \"2013-11-20 10:33:23\",\n \"is_required\": 0,\n \"is_static\": 1,\n \"field_order\": 1\n ],\n [\n \"id\": 23,\n \"menu_id\": 1,\n \"field_type_id\": 1,\n \"c4w_code\": \"1234\",\n \"field_label\": \"Company Name\",\n \"field_values\": \"\",\n \"date_Created\": \"2012-09-16 05:11:56\",\n \"date_modified\": \"2013-11-20 10:33:23\",\n \"is_required\": 1,\n \"is_static\": 1,\n \"field_order\": 3\n ]\n\n}";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        context = this;
        Log.i("Json String for testing", "" + jsonObjectString);
    }

    private void getCustomerMenuFieldsData(String parameter) {
        menuFieldInstance = gson.fromJson(jsonObjectString, MenuFields[].class);
        for (int i = 0; i < jsonObjectString.length(); i++) {
            Log.i("menuField Instance ", "" + menuFieldInstance[i].getId());
        }
    }
}

请忽略花括号的错误.我得到Error.Here是Logcat:

12-30 23:30:29.190: E/AndroidRuntime(15833): FATAL EXCEPTION: AsyncTask #3
12-30 23:30:29.190: E/AndroidRuntime(15833): java.lang.RuntimeException: An error occured while executing doInBackground()
12-30 23:30:29.190: E/AndroidRuntime(15833):    at android.os.AsyncTask$3.done(AsyncTask.java:299)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at java.util.concurrent.FutureTask$Sync.innerSetException(FutureTask.java:273)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at java.util.concurrent.FutureTask.setException(FutureTask.java:124)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:307)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at java.util.concurrent.FutureTask.run(FutureTask.java:137)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:230)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at java.lang.Thread.run(Thread.java:856)
12-30 23:30:29.190: E/AndroidRuntime(15833): Caused by: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.google.gson.Gson.fromJson(Gson.java:815)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.google.gson.Gson.fromJson(Gson.java:768)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.google.gson.Gson.fromJson(Gson.java:717)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.google.gson.Gson.fromJson(Gson.java:689)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.survey.management.activity.MainActivity$RequestForCustomerMenuFields.getCustomerMenuFieldsData(MainActivity.java:480)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.survey.management.activity.MainActivity$RequestForCustomerMenuFields.doInBackground(MainActivity.java:456)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.survey.management.activity.MainActivity$RequestForCustomerMenuFields.doInBackground(MainActivity.java:1)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at android.os.AsyncTask$2.call(AsyncTask.java:287)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
12-30 23:30:29.190: E/AndroidRuntime(15833):    ... 5 more
12-30 23:30:29.190: E/AndroidRuntime(15833): Caused by: java.lang.IllegalStateException: Expected BEGIN_ARRAY but was BEGIN_OBJECT at line 1 column 2
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.google.gson.stream.JsonReader.beginArray(JsonReader.java:338)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.google.gson.internal.bind.ArrayTypeAdapter.read(ArrayTypeAdapter.java:70)
12-30 23:30:29.190: E/AndroidRuntime(15833):    at com.google.gson.Gson.fromJson(Gson.java:803)
12-30 23:30:29.190: E/AndroidRuntime(15833):    ... 13 more

此行错误:

menuFieldInstance = gson.fromJson(jsonObjectString,MenuFields[].class);

Answer 1

首先你的jsonString无效.您可以在http://jsonviewer.stack.hu/进行测试.我修改了一下以使其有效:

final GsonBuilder builder = new GsonBuilder();
final Gson gson = builder.create();

String jsonObjectString ="{\"menu_fields\":[{\"id\": 22, \"menu_id\": 1, \"field_type_id\": 1, \"c4w_code\": \"1234\", \"field_label\": \"Customer No\", \"field_values\": \"\", \"date_created\": \"2012-09-16 05:11:23\", \"date_modified\": \"2013-11-20 10:33:23\", \"is_required\": 0, \"is_static\": 1, \"field_order\": 1 }, {\"id\": 23, \"menu_id\": 1, \"field_type_id\": 1, \"c4w_code\": \"1234\", \"field_label\": \"Company Name\", \"field_values\": \"\", \"date_created\": \"2012-09-16 05:11:56\", \"date_modified\": \"2013-11-20 10:33:23\", \"is_required\": 1, \"is_static\": 1, \"field_order\": 3 }]}";
try {
    MenuFieldHolder menuFieldHolder= gson.fromJson(jsonObjectString, MenuFieldHolder.class);
    Log.i("TAG", "Result: " + menuFieldHolder.toString());
} catch (Throwable t) {
    t.printStackTrace();
}

你的MenuFieldHolder和MenuField课程应如下所示:

private class MenuFieldHolder {
    @SerializedName("menu_fields") 
    private MenuField[] menuFields;
}

private class MenuField {
    private int id;

    @SerializedName("menu_id") 
    private int menuId;

    @SerializedName("field_type") 
    private int fieldType;

    @SerializedName("c4w_code") 
    private String c4wCode;

    @SerializedName("field_label") 
    private String fieldLabel;

    @SerializedName("field_values") 
    private String fieldValues;

    @SerializedName("date_created") 
    private String dateCreated;

    @SerializedName("date_modified") 
    private String dateModified;

    @SerializedName("is_required") 
    private int isRequired;

    @SerializedName("is_static") 
    private int isStatic;

    @SerializedName("field_order") 
    private String fieldOrder;
}

或者没有SerializedName注释(我更喜欢上面.因为使用camel case字段名称是Java的最佳实践):

private class MenuFieldHolder {
    private MenuField[] menu_fields;
}

private class MenuField {
    private int id;

    private int menu_id;

    private int field_type;

    private String c4w_code;

    private String field_label;

    private String field_values;

    private String date_created;

    private String date_modified;

    private int is_required;

    private int is_static;

    private String field_order;
}