Question

我尝试使用api显示从数据库返回的项目列表，并且在浏览器中工作正常，我也可以返回单个项目而没有任何问题，尝试返回整个列表并将其放入Java中代码给我带来很多问题。我的代码真的搞砸了，我不确定问题出在哪里，但我想是，它无法正确存储返回的值。

MainPageActivity：

public class MainPageActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main_page);

        final ListView listView = (ListView) findViewById(R.id.ListListaEvenata);

        if(EventiLista.getListaEvenata()==null) {
            postaviEvente();
        }

        listView.setAdapter(new BaseAdapter() {
            @Override
            public int getCount() {
                if(EventiLista.getListaEvenata()!=null)
                return EventiLista.getListaEvenata().size();

                else return 0;
            }

            @Override
            public Object getItem(int position) {
                return EventiLista.getListaEvenata().get(position);
            }

            @Override
            public long getItemId(int position) {
                return position;
            }

            @Override
            public View getView(int position, View convertView, ViewGroup parent) {


                final Eventi x = EventiLista.getListaEvenata().get(position);

                final LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

                View view = inflater.inflate(R.layout.eventistavka, parent, false);

                TextView Naziv = (TextView) view.findViewById(R.id.EventNaziv);

                TextView Opis = (TextView) view.findViewById(R.id.OpisEventa);

                Naziv.setText(x.Naziv);

                Opis.setText(x.Opis);

                return null;
            }
        });
    }

    protected void postaviEvente() {
        EventiApi.GetEvente(this, new MyRunnable<List<Eventi>>() {


            @Override
            public void run(List<Eventi> result) {
                EventiLista.setListaEvenata(result);
            }
        });
    }

这也是我的EventiApi类，可能是引起问题的类：

public class EventiApi {
public static List<Eventi> listEventi = EventiLista.getListaEvenata();
    public static List<Eventi> GetEvente(final Context context, final MyRunnable<List<Eventi>> onSuccess) {
        if(listEventi==null) {
        new AsyncTask<Void, Void, List<Eventi>>() {


            @Override
            protected List<Eventi> doInBackground(Void... voids) {
                HttpGet httpGet = new HttpGet(Config.url + "api/Eventi");

                DefaultHttpClient client = new DefaultHttpClient();


                try {
                    HttpResponse response = client.execute(httpGet);

                    InputStream inputStream = response.getEntity().getContent();

                    String strJson = convertStreamToString(inputStream);

                    Eventi x = MyGson.build().fromJson(strJson, Eventi.class);

                    listEventi.add(x);
                } catch (IOException e) {
                    Log.e("HttpManager", e.getMessage());

                    EventiLista.setListaEvenata(null);

                }
                return listEventi;
            }


            protected void onPostExecute(List<Eventi> rezultat) {
                if (rezultat == null)
                    Toast.makeText(MyApp.getContext(), "Greska u komunikaciji sa serverom", Toast.LENGTH_SHORT).show();
                else {
                    onSuccess.run(rezultat);
                }

            }
        }.execute();


    }
    return listEventi;
    }
    public static String convertStreamToString(InputStream inputStream) throws IOException {
        String newLine = System.getProperty("line.separator");
        BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));
        StringBuilder result = new StringBuilder();
        boolean flag = false;
        for (String line; (line = reader.readLine()) != null; ) {
            result.append(flag ? newLine : "").append(line);
            flag = true;
        }
        return result.toString();
    }
}

这也是我的MyRunnable界面：

public interface MyRunnable<T> {

    void run(T result);
}

还有我的EventiLista帮助器类：

public class EventiLista {
    private static List<Eventi> listaEvenata;

    public static List<Eventi> getListaEvenata() {
        return listaEvenata;
    }

    public static void setListaEvenata(List<Eventi> listaEvenata) {
        EventiLista.listaEvenata = listaEvenata;
    }
}

MyGson：

public class MyGson {
    public static Gson build()
    {
        GsonBuilder builder = new GsonBuilder();
        builder.setDateFormat("yyyy-MM-dd'T'HH:mm:ss");
        return builder.create();
    }
}

任何帮助或想法都将受到高度赞赏，谢谢大家的宝贵时间！

它应该在我的列表中显示返回的值，但应用程序刚刚坏了。

这是logcat的一部分：

Process: com.example.evente, PID: 6151
    java.lang.RuntimeException: An error occurred while executing doInBackground()
        at android.os.AsyncTask$3.done(AsyncTask.java:353)
        at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:383)
        at java.util.concurrent.FutureTask.setException(FutureTask.java:252)
        at java.util.concurrent.FutureTask.run(FutureTask.java:271)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636)
        at java.lang.Thread.run(Thread.java:764)
     Caused by: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2 path $
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:224)
        at com.google.gson.Gson.fromJson(Gson.java:888)
        at com.google.gson.Gson.fromJson(Gson.java:853)
        at com.google.gson.Gson.fromJson(Gson.java:802)
        at com.google.gson.Gson.fromJson(Gson.java:774)
        at com.example.evente.api.EventiApi$1.doInBackground(EventiApi.java:46)
        at com.example.evente.api.EventiApi$1.doInBackground(EventiApi.java:29)
        at android.os.AsyncTask$2.call(AsyncTask.java:333)
        at java.util.concurrent.FutureTask.run(FutureTask.java:266)
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) 
        at java.lang.Thread.run(Thread.java:764) 
     Caused by: java.lang.IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY at line 1 column 2 path $
        at com.google.gson.stream.JsonReader.beginObject(JsonReader.java:385)
        at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:213)
        at com.google.gson.Gson.fromJson(Gson.java:888) 
        at com.google.gson.Gson.fromJson(Gson.java:853) 
        at com.google.gson.Gson.fromJson(Gson.java:802) 
        at com.google.gson.Gson.fromJson(Gson.java:774) 
        at com.example.evente.api.EventiApi$1.doInBackground(EventiApi.java:46) 
        at com.example.evente.api.EventiApi$1.doInBackground(EventiApi.java:29) 
        at android.os.AsyncTask$2.call(AsyncTask.java:333) 
        at java.util.concurrent.FutureTask.run(FutureTask.java:266) 
        at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:245) 
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1162) 
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:636) 
        at java.lang.Thread.run(Thread.java:764)

Answer 1

您进入String strJson = convertStreamToString(inputStream);的响应是JsonArray，您正在使用Eventi x = MyGson.build().fromJson(strJson, Eventi.class);将其转换为模型对象

这就是为什么它引发异常IllegalStateException: Expected BEGIN_OBJECT but was BEGIN_ARRAY

的原因

Answer 2

我建议对HTTP请求使用翻新 https://square.github.io/retrofit/

无法显示api返回的项目列表

2 个答案: