Android 如何从一个单独的Asynctask类到另一个fragment类获取onPostExecute的结果？

我尝试了它，但它并没有显示任何内容，我想我不知道如何从单独的AsyncTask类到fragment类获取onPostExecute方法的结果。 请帮帮我

public class MainActivity extends AppCompatActivity {

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

        getFragmentManager()
                .beginTransaction()
                .add(R.id.Fragment_Container, new ForecastFragment(),
                        ForecastTask.class.getSimpleName())
                .commit();

    }

2-异步任务类

public class ForecastTask extends AsyncTask<String, String, `List<MovieModel>> {`

    private final String LOG_TAG = ForecastTask.class.getSimpleName();
    private List<MovieModel> movieModelList;
    public AsyncResponse delegate=null;

    public ForecastTask(AsyncResponse listener) {
        delegate = listener;
    }

    @Override
    protected List<MovieModel> doInBackground(String... params) {
        if (params.length == 0) {
            return null;
        }

        HttpURLConnection connection = null;
        BufferedReader reader = null;

        try {
            URL url = new URL(param[0]);
            connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.connect();

            InputStream inputStream = connection.getInputStream();
            if (inputStream == null) {
                return null;
            }

            reader = new BufferedReader(new InputStreamReader(inputStream));
            StringBuffer buffer = new StringBuffer();
            String line;
            while ((line = reader.readLine()) != null) {
                buffer.append(line);
            }

            JSONObject jsonObject = new JSONObject(buffer.toString());
            JSONArray jsonArray = jsonObject.getJSONArray("results");

            movieModelList= new ArrayList<>();
            //adding JSON Array data into MovieModel Class object
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject finalObject = jsonArray.getJSONObject(i);
                MovieModel movieModel = new MovieModel();
                movieModel.setId(finalObject.getInt("id"));
                movieModel.setTitle(finalObject.getString("title"));
                movieModel.setPoster_path(finalObject.getString("poster_path"));

            }
            return movieModelList;
        } catch (JSONException | IOException e) {
            e.printStackTrace();
        } finally {
            if (connection != null) {
                connection.disconnect();
            }
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return null;
    }

    public ForecastTask() {
        super();
    }

    @Override
    protected void onPostExecute( List<MovieModel> movieModels) {
        delegate.processFinish(movieModels);
    }
}

公共类ForecastTask扩展了AsyncTask{`
private final String LOG_TAG=ForecastTask.class.getSimpleName（）；
私有列表电影模型列表；
公共异步响应委托=null；
公共预测任务（异步响应侦听器）{
代表=听众；
}
@凌驾
受保护列表doInBackground（字符串…参数）{
如果（params.length==0）{
返回null；
}
HttpURLConnection=null；
BufferedReader reader=null；
试一试{
URL=新URL（参数[0]）；
connection=（HttpURLConnection）url.openConnection（）；
connection.setRequestMethod（“GET”）；
connection.connect（）；
InputStream InputStream=connection.getInputStream（）；
如果（inputStream==null）{
返回null；
}
reader=新的BufferedReader（新的InputStreamReader（inputStream））；
StringBuffer=新的StringBuffer（）；
弦线；
而（（line=reader.readLine（））！=null）{
buffer.append（行）；
}
JSONObject JSONObject=新的JSONObject（buffer.toString（））；
JSONArray JSONArray=jsonObject.getJSONArray（“结果”）；
movieModelList=新的ArrayList（）；
//将JSON数组数据添加到MovieModel类对象中
for（int i=0；i

3-片段类

public class ForecastFragment extends Fragment implements AsyncResponse {

    private String Popular = "http://api.themoviedb.org/3/discover/movie?sort_by=popularity.desc&api_key=xxxxxxxxxxxxxxxxxxxxxxxxxx";

    private List<MovieModel> movieModels;
    private static final String STATE_MOVIES ="state_movies";
    CustomAdapter customAdapter=null;
    GridView gridView=null;
    View rootView=null;
    ForecastTask forecastTask;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setHasOptionsMenu(true);
    }    

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.activity_main, container, false);
        gridView=(GridView)rootView.findViewById(R.id.gridView);
        movieModels=new ArrayList<MovieModel>();
            forecastTask=new ForecastTask(this);
            forecastTask.delegate = this;
            forecastTask.execute(Popular);

        customAdapter = new CustomAdapter(getActivity(), movieModels);
        gridView.setAdapter(customAdapter);   

        return rootView;
    }

    @Override
    public void processFinish(List<MovieModel> movieModels) {
        this.movieModels=movieModels;
    }
}

公共类ForecastFragment扩展片段实现异步响应{
私有字符串Popular=”http://api.themoviedb.org/3/discover/movie?sort_by=popularity.desc&api_key=xxxxxxxxxxxxxxxxxxxxxxxxxx";
私人名单电影模型；
私有静态最终字符串STATE\u MOVIES=“STATE\u MOVIES”；
CustomAdapter=null；
GridView GridView=null；
视图rootView=null；
预报任务预报任务；
@凌驾
创建时的公共void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
设置选项菜单（真）；
}    
@凌驾
CreateView上的公共视图（布局、充气机、视图组容器、捆绑包保存状态）{
rootView=充气机。充气（R.layout.activity\u main，container，false）；
gridView=（gridView）rootView.findviewbyd（R.id.gridView）；
movieModels=newarraylist（）；
forecastTask=新的forecastTask（此）；
forecastTask.delegate=此；
forecastTask.execute（流行）；
customAdapter=新的customAdapter（getActivity（），movieModels）；
setAdapter（customAdapter）；
返回rootView；
}
@凌驾
public void processFinish（列出电影模型）{
this.movieModels=movieModels；
}
}

4-异步响应接口

public interface AsyncResponse {
    void processFinish(List<MovieModel> movieModels);
}

公共接口异步响应{
void processFinish（列出电影模型）；
}

您没有在

电影模型列表中添加
电影
项。这就是为什么它仍然是空的。您必须修改如下内容-

movieModelList= new ArrayList<>();
            //adding JSON Array data into MovieModel Class object
            for (int i = 0; i < jsonArray.length(); i++) {
                JSONObject finalObject = jsonArray.getJSONObject(i);
                MovieModel movieModel = new MovieModel();
                movieModel.setId(finalObject.getInt("id"));
                movieModel.setTitle(finalObject.getString("title"));
                movieModel.setPoster_path(finalObject.getString("poster_path"));


movieModelList.add(movieModel); //Add this line 




            }

如何从单独的Asynctask类到单独的fragment类获取结果？请帮助我…movieModelList=new ArrayList（）；对于（int i=0；i @Override
    public void processFinish(List<MovieModel> movieModels) {
        this.movieModels=movieModels;
        customAdapter = new CustomAdapter(getActivity(), movieModels);
        gridView.setAdapter(customAdapter);
    }