在onpostexecute之后，Android Custom ArrayAdapter变为null

Question

我正在尝试从API获取数据，然后在gridview上显示图像。

我可以从api获取数据并将值（url image）放到我在onpostexecute方法上创建的自定义适配器上。

但它没有在网格上显示任何内容。值为空

我一直在寻找这个解决方案两天

有人可以帮我解决这个问题吗？

这是我的代码：

MainActivityFragment.java

    public class MainActivityFragment extends Fragment {

    private MovieAdapter movieAdapter;
    MovieList[] movieList;

    public MainActivityFragment() {

    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        final View rootView = inflater.inflate(R.layout.fragment_main, container, false);

        movieAdapter = new MovieAdapter(getActivity(), new ArrayList<MovieList>());

        GridView gridView = (GridView) rootView.findViewById(R.id.grid_view);
        gridView.setAdapter(movieAdapter);

        return rootView;
    }

    public void fetchMoviesData(){
        try {

            SharedPreferences perf = PreferenceManager.getDefaultSharedPreferences(getActivity());
            String sortCateg = perf.getString(getString(R.string.pref_sort_key), getString(R.string.sort_value_popular));

            fetchMovieDataTask fwd = new fetchMovieDataTask();
            fwd.execute(sortCateg).get();

        }catch(Exception e){
            Toast.makeText(getActivity(),"Failed retreive movies data!",Toast.LENGTH_SHORT).show();
        }
    }

    @Override
    public void onStart() {
        super.onStart();
        fetchMoviesData();

    }

    public class fetchMovieDataTask extends AsyncTask<String,Void,MovieList[]>{

        private final String LOG_TAG = fetchMovieDataTask.class.getSimpleName();

        @Override
        protected MovieList[] doInBackground(String... params) {
            HttpURLConnection urlConnection = null;
            BufferedReader bufferedReader = null;

            String movieStr = null;
            String sortOrder = params[0];

            try{


                final String BASE_URL = "http://api.themoviedb.org/3/movie/"+sortOrder;
                final String API_KEY = "api_key";

                Uri buildUri = Uri.parse(BASE_URL).buildUpon()
                        .appendQueryParameter(API_KEY,BuildConfig.theMovieDbApiKey)
                        .build();

                URL url = new URL(buildUri.toString());

                urlConnection = (HttpURLConnection) url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();

                InputStream inputStream = urlConnection.getInputStream();
                StringBuffer stringBuffer = new StringBuffer();

                if(inputStream == null){
                    movieStr = null;
                }
                bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

                String line;
                while((line = bufferedReader.readLine()) != null){
                    stringBuffer.append(line + "\n");
                }

                if(stringBuffer.length() == 0){
                    return null;
                }

                movieStr = stringBuffer.toString();
            }catch(IOException e){
                Log.e(LOG_TAG,"Error",e);
                movieStr = null;
            }finally {
                if(urlConnection != null){
                    urlConnection.disconnect();
                }

                if(bufferedReader != null){
                    try{
                        bufferedReader.close();
                    }catch(final  IOException e){
                        Log.e(LOG_TAG,"Error Closing Reader",e);
                    }
                }
            }

            try{
                return getMoviePosterFromJson(movieStr);
            }catch(JSONException e){
                Log.e(LOG_TAG,e.getMessage(),e);
                e.printStackTrace();
            }

            return null;
        }

        @Override
        protected void onPostExecute(MovieList[] result) {
            if(result != null){
                movieAdapter.clear();
                movieAdapter = new MovieAdapter(getActivity(), Arrays.asList(result)); 
            }
        }

        private Date stringToDate(String aDate,String aFormat) {

            if(aDate==null) return null;
            ParsePosition pos = new ParsePosition(0);
            SimpleDateFormat simpledateformat = new SimpleDateFormat(aFormat);
            Date stringDate = simpledateformat.parse(aDate, pos);
            return stringDate;

        }

        private MovieList[] getMoviePosterFromJson(String movieJsonStr)
                throws JSONException {

            final String BASE_URL = "http://image.tmdb.org/t/p/w185";
            final String TMDb_RESULT = "results";
            final String TMDb_POSTER  = "poster_path";
            final String TMDb_TITLE  = "original_title";
            final String TMDb_DATE  = "release_date";
            final String TMDb_VOTE  = "vote_average";
            final String TMDb_OVERVIEW  = "overview";


            JSONObject movieJson = new JSONObject(movieJsonStr);
            JSONArray movieArray = movieJson.getJSONArray(TMDb_RESULT);

            movieList = new MovieList[movieArray.length()];


            for(int i = 0; i < movieArray.length() - 1; i++) {
                String title;
                String poster;
                Integer year;
                String rating;
                String overview;


                JSONObject movieObject = movieArray.getJSONObject(i);
                poster = BASE_URL + movieObject.getString(TMDb_POSTER);
                title = movieObject.getString(TMDb_TITLE);
                year = stringToDate(movieObject.getString(TMDb_DATE),"yyy-MM-dd").getYear();
                rating = movieObject.getString(TMDb_VOTE);
                overview = movieObject.getString(TMDb_OVERVIEW);

                movieList[i] = new MovieList(title,poster,year,rating,overview);
            }

            return movieList;
        }
    }
}

编辑2：

public class MainActivityFragment extends Fragment {

public MovieAdapter movieAdapter;
MovieList[] movieList;

public MainActivityFragment() {

}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    final View rootView = inflater.inflate(R.layout.fragment_main, container, false);

    movieAdapter = new MovieAdapter(getActivity(), new ArrayList<MovieList>());

    GridView gridView = (GridView) rootView.findViewById(R.id.grid_view);
    gridView.setAdapter(movieAdapter);
    fetchMoviesData();

    return rootView;
}

public void fetchMoviesData(){
    try {

        SharedPreferences perf = PreferenceManager.getDefaultSharedPreferences(getActivity());
        String sortCateg = perf.getString(getString(R.string.pref_sort_key), getString(R.string.sort_value_popular));

        fetchMovieDataTask fwd = new fetchMovieDataTask();
        fwd.execute(sortCateg).get();

    }catch(Exception e){
        Toast.makeText(getActivity(),"Failed retreive movies data!",Toast.LENGTH_SHORT).show();
    }
}

@Override
public void onStart() {
    super.onStart();

}

public class fetchMovieDataTask extends AsyncTask<String,Void,MovieList[]>{

    private final String LOG_TAG = fetchMovieDataTask.class.getSimpleName();

    @Override
    protected MovieList[] doInBackground(String... params) {
        HttpURLConnection urlConnection = null;
        BufferedReader bufferedReader = null;

        String movieStr = null;
        String sortOrder = params[0];

        try{
            //http://api.themoviedb.org/3/movie/popular?api_key=e4a8053d4e3bab726a20dcb2c12897f3

            final String BASE_URL = "http://api.themoviedb.org/3/movie/"+sortOrder;
            final String API_KEY = "api_key";

            Uri buildUri = Uri.parse(BASE_URL).buildUpon()
                    .appendQueryParameter(API_KEY,BuildConfig.theMovieDbApiKey)
                    .build();

            URL url = new URL(buildUri.toString());

            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.connect();

            InputStream inputStream = urlConnection.getInputStream();
            StringBuffer stringBuffer = new StringBuffer();

            if(inputStream == null){
                movieStr = null;
            }
            bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

            String line;
            while((line = bufferedReader.readLine()) != null){
                stringBuffer.append(line + "\n");
            }

            if(stringBuffer.length() == 0){
                return null;
            }

            movieStr = stringBuffer.toString();
        }catch(IOException e){
            Log.e(LOG_TAG,"Error",e);
            movieStr = null;
        }finally {
            if(urlConnection != null){
                urlConnection.disconnect();
            }

            if(bufferedReader != null){
                try{
                    bufferedReader.close();
                }catch(final  IOException e){
                    Log.e(LOG_TAG,"Error Closing Reader",e);
                }
            }
        }

        try{
            return getMoviePosterFromJson(movieStr);
        }catch(JSONException e){
            Log.e(LOG_TAG,e.getMessage(),e);
            e.printStackTrace();
        }

        return null;
    }

    @Override
    protected void onPostExecute(MovieList[] result) {
        if(result != null){
            GridView gridView = (GridView) getActivity().findViewById(R.id.grid_view);

            movieAdapter = new MovieAdapter(getActivity(), Arrays.asList(result));
            gridView.setAdapter(movieAdapter);
        }
    }

    private Date stringToDate(String aDate,String aFormat) {

        if(aDate==null) return null;
        ParsePosition pos = new ParsePosition(0);
        SimpleDateFormat simpledateformat = new SimpleDateFormat(aFormat);
        Date stringDate = simpledateformat.parse(aDate, pos);
        return stringDate;

    }

    private MovieList[] getMoviePosterFromJson(String movieJsonStr)
            throws JSONException {

        final String BASE_URL = "http://image.tmdb.org/t/p/w185";
        final String TMDb_RESULT = "results";
        final String TMDb_POSTER  = "poster_path";
        final String TMDb_TITLE  = "original_title";
        final String TMDb_DATE  = "release_date";
        final String TMDb_VOTE  = "vote_average";
        final String TMDb_OVERVIEW  = "overview";


        JSONObject movieJson = new JSONObject(movieJsonStr);
        JSONArray movieArray = movieJson.getJSONArray(TMDb_RESULT);

        movieList = new MovieList[movieArray.length()];


        for(int i = 0; i < movieArray.length() - 1; i++) {
            String title;
            String poster;
            Integer year;
            String rating;
            String overview;


            JSONObject movieObject = movieArray.getJSONObject(i);
            poster = BASE_URL + movieObject.getString(TMDb_POSTER);
            title = movieObject.getString(TMDb_TITLE);
            year = stringToDate(movieObject.getString(TMDb_DATE),"yyy-MM-dd").getYear();
            rating = movieObject.getString(TMDb_VOTE);
            overview = movieObject.getString(TMDb_OVERVIEW);

            movieList[i] = new MovieList(title,poster,year,rating,overview);
        }

        return movieList;
    }
}

} ERROR EDIT 2

E/AndroidRuntime: FATAL EXCEPTION: main
                                                                              java.lang.NullPointerException
                                                                                  at com.example.william.themovieapps.MainActivityFragment$fetchMovieDataTask.onPostExecute(MainActivityFragment.java:174)
                                                                                  at com.example.william.themovieapps.MainActivityFragment$fetchMovieDataTask.onPostExecute(MainActivityFragment.java:95)
                                                                                  at android.os.AsyncTask.finish(AsyncTask.java:631)
                                                                                  at android.os.AsyncTask.access$600(AsyncTask.java:177)
                                                                                  at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:644)
                                                                                  at android.os.Handler.dispatchMessage(Handler.java:99)
                                                                                  at android.os.Looper.loop(Looper.java:137)
                                                                                  at android.app.ActivityThread.main(ActivityThread.java:5103)
                                                                                  at java.lang.reflect.Method.invokeNative(Native Method)
                                                                                  at java.lang.reflect.Method.invoke(Method.java:525)
                                                                                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
                                                                                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
                                                                                  at dalvik.system.NativeStart.main(Native Method)

Answer 1

onPostExecute 应如下所示：

@Override
    protected void onPostExecute(MovieList[] result) {
        if(result != null){
            movieAdapter = new MovieAdapter(getActivity(), Arrays.asList(result)); 
            gridView.setAdapter(movieAdapter);
        }
    }

修改1：

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    MovieList movieList = getItem(position);

    convertView = LayoutInflater.from(getContext()).inflate(R.layout.poster_griditem_layout,parent,false);

    Picasso
            .with(getContext())
            .load(movieList.poster)
            .fit()
            .into((ImageView) convertView);

    return convertView;
}

编辑2：

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    final View rootView = inflater.inflate(R.layout.fragment_main, container, false);

    movieAdapter = new MovieAdapter(getActivity(), new ArrayList<MovieList>());

    GridView gridView = (GridView) rootView.findViewById(R.id.grid_view);
    gridView.setAdapter(movieAdapter);
    fetchMoviesData();

    return rootView;
}

@Override
public void onStart() {
    super.onStart();

}

希望这会对你有所帮助。

Answer 2

@Hiren Patel，这是我的代码和logcat： Logcat

MovieAdapter.java

@Column(columnDefinition="BLOB NOT NULL")
@MapKeyColumn(columnDefinition="BLOB NOT NULL")

}

Answer 3

抱歉，伙计们我的错误。我在我的数组中的数据。现在解决它。感谢所有的帮助