我第一次使用GSON进行改造。它使用静态数据运行流畅但在动态数据的情况下显示上述错误。在设置文本值时适配器中显示错误
MainActivity
public class MainActivity extends AppCompatActivity {
String Navigation_Url = "http://www.xxxxxxxx.com";
ListView listView;
ArrayList<ListPojo> listPojos = new ArrayList<>();
ListRetrofitAndroid listRetrofitAndroid;
ArrayList countries = new ArrayList();
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listView = (ListView) findViewById(R.id.listView);
getRetrofitData();
}
void getRetrofitData() {
Retrofit retrofit = new Retrofit.Builder().baseUrl(Navigation_Url).addConverterFactory(GsonConverterFactory.create()).build();
CountryArrayAPI api = retrofit.create(CountryArrayAPI.class);
Call<List> call = api.getCountries();
call.enqueue(new Callback<List>() {
@Override
public void onResponse(Call<List> call, Response<List> response) {
Gson gson = new Gson();
try {
listPojos = (ArrayList) response.body();
System.out.println("the ArrayList is" + listPojos);
// ArrayList<ListPojo> merchantOfferModels = gson.fromJson(response, new TypeToken<ListPojo>() {}.getType());
listRetrofitAndroid = new ListRetrofitAndroid(getApplicationContext(), listPojos);
listView.setAdapter(listRetrofitAndroid);
} catch (Exception e) {
Log.d("onResponse", "There is an error");
e.printStackTrace();
}
}
@Override
public void onFailure(Call<List> call, Throwable t) {
Log.d("Failure", t.toString());
}
});
}
}
ListRetrofitAndroid（适配器）
public class ListRetrofitAndroid extends BaseAdapter {
Context mContext;
ArrayList<ListPojo> arrayList = new ArrayList<>();
String TAG = "HomeTab_adapter";
public ListRetrofitAndroid(Context context, ArrayList<ListPojo> listPojos) {
super();
this.mContext = context;
this.arrayList = listPojos;
}
@Override
public int getCount() {
return arrayList.size();
}
@Override
public Object getItem(int position) {
return arrayList.get(position);
}
@Override
public long getItemId(int position) {
return position;
}
@Override
public View getView(final int position, View convertView, ViewGroup parent) {
final Holder viewHolder;
if (convertView == null) {
LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
// convertView = inflater.inflate(R.layout.list, parent, false);
convertView = inflater.inflate(R.layout.listview_item, parent, false);
// well set up the ViewHolder
// viewHolder = new ClassScheduleStudentAdapter.Holder();
viewHolder = new Holder();
viewHolder.textName = convertView.findViewById(R.id.list_item_main);
convertView.setTag(viewHolder);
} else {
viewHolder = (Holder) convertView.getTag();
}
viewHolder.textName.setText(arrayList.get(position).getTitle());
return convertView;
}
class Holder {
TextView textName;
}
}
模型（ListPojo）
public class ListPojo {
String title;
public ListPojo(String title) {
this.title = title;
}
public String getTitle() {
return title;
}
}
接口
public interface CountryArrayAPI {
@GET("/api/popular_destinations")
public Call<List> getCountries();
}
JSON
[
{
"id": 1,
"title": "Hiranya Varna Mahavihar",
"location": "Kwalakhu Rd, Patan 44600, Nepal",
"main_image": "images/popular_places/patan-durbar-square.jpg"
},
{
"id": 2,
"title": "Yasodhar Mahavihar-Bubahal",
"location": "Jana Bahal Rd, Patan 44600, Nepal",
"main_image": "images/popular_places/patan-durbar-square.jpg"
},
{
"id": 3,
"title": "Krishna Temple Sundhara",
"location": "Tyagal - Lalitpur Rd, Patan 44600, Nepal",
"main_image": "images/popular_places/Patan-2.jpg"
},
{
"id": 4,
"title": "Hiranya Varna Mahavihar",
"location": "Kwalakhu Rd, Patan 44600, Nepal",
"main_image": "images/popular_places/asd.jpg"
}
]
StsckTrace
09-19 05:15:32.475 18949-18949/com.example.user_pc.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.user_pc.myapplication, PID: 18949
java.lang.ClassCastException: com.google.gson.internal.LinkedTreeMap cannot be cast to com.example.user_pc.myapplication.pojo.ListPojo
at com.example.user_pc.myapplication.adpater.ListRetrofitAndroid.getView(ListRetrofitAndroid.java:71)
at android.widget.AbsListView.obtainView(AbsListView.java:2255)
at android.widget.ListView.measureHeightOfChildren(ListView.java:1263)
at android.widget.ListView.onMeasure(ListView.java:1175)
at android.view.View.measure(View.java:16497)
at android.support.constraint.ConstraintLayout.internalMeasureChildren(ConstraintLayout.java:934)
at android.support.constraint.ConstraintLayout.onMeasure(ConstraintLayout.java:973)
at android.view.View.measure(View.java:16497)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:139)
at android.view.View.measure(View.java:16497)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
at android.support.v7.widget.ActionBarOverlayLayout.onMeasure(ActionBarOverlayLayout.java:391)
at android.view.View.measure(View.java:16497)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at android.view.View.measure(View.java:16497)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1404)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:695)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:588)
at android.view.View.measure(View.java:16497)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5125)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:310)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2291)
at android.view.View.measure(View.java:16497)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:1912)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1109)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1291)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:996)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5600)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:761)
at android.view.Choreographer.doCallbacks(Choreographer.java:574)
at android.view.Choreographer.doFrame(Choreographer.java:544)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:747)
at android.os.Handler.handleCallback(Handler.java:733)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:136)
at android.app.ActivityThread.main(ActivityThread.java:5001)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:785)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
at dalvik.system.NativeStart.main(Native Method)
如何解决这个问题？
答案 0 :(得分：4)
您正在使用ArrayList<ListPojo>，因此您需要确保使用正确类型List<ListPojo>而不是没有类型的list进行解析
由于缺少类型信息，gson在内部返回List
创建了对象LinkedTreeMap，因为你正在使用raw类型（应该是对未经检查的强制转换的警告），声明为具体类型，当适配器实际期望PojoObject但在内部时它会产生问题别的东西。所以解决方案
Never use raw-types anywhere possible
所以
public interface CountryArrayAPI {
@GET("api/popular_destinations")
public Call<List<ListPojo>> getCountries();
}
并在/之前删除api，并且调用将像
call.enqueue(new Callback<List<ListPojo>>() {
@Override
public void onResponse(Call<List<ListPojo>> call, Response<List<ListPojo>> response) {
listPojos = response.body();
始终代码为interface所以
List<ListPojo> listPojos = ...;
答案 1 :(得分：1)
我目前还不知道如何使用List来处理json。但你可以使用这样的数组：
public interface CountryArrayAPI {
@GET("/api/popular_destinations")
public Call<ListPojo[]> getCountries();
}