我一直在拍电影应用程序（用于学习上udacity机器人BTW项目工作）。我遇到了一些问题，但按照线程这类Unable修改ArrayAdapter中的ListView：UnsupportedOperationException异常

不过，虽然我的应用程序不会崩溃，图像不加载，我无法找出原因。这里是我的code：

布局XML文件movies_item.xml

 ＆LT;？XML版本=1.0编码=UTF-8＆GT？;＆LT; ImageView的的xmlns：机器人=htt​​p://schemas.android.com/apk/res/android    机器人：layout_width =WRAP_CONTENT    机器人：layout_height =WRAP_CONTENT    机器人：ID =@ + ID / movies_item_thumbnail    ＆GT;＆LT; / ImageView的＆GT; 

fragment_main.xml

 ＆LT;的FrameLayout的xmlns：机器人=htt​​p://schemas.android.com/apk/res/android    的xmlns：工具=htt​​p://schemas.android.com/tool​​s的android：layout_width =match_parent    机器人：layout_height =match_parent机器人：paddingLeft =@扪/ activity_horizo​​ntal_margin    机器人：paddingRight =@扪/ activity_horizo​​ntal_margin    机器人：paddingTop =@扪/ activity_vertical_margin    机器人：paddingBottom会=@扪/ activity_vertical_margin    工具：上下文=com.example.cindy.popularmovies.MoviesFragment＆GT;    ＆LT; GridView控件        机器人：ID =@ + ID / movies_gridview        机器人：layout_width =match_parent        机器人：layout_height =match_parent        机器人：为numColumns =auto_fit        机器人：比重=中心        /＆GT;＆LT; /＆的FrameLayout GT; 

MovieArrayAdapter.java

 公共类MovieArrayAdapter扩展ArrayAdapter＆LT;电影及GT; {        私人最终上下文的背景下;        私人最终名单＆LT;电影及GT;电影;        公共MovieArrayAdapter（上下文的背景下，列表与LT;电影＆GT;电影）{            超（背景下，0，电影）;            this.context =背景;            this.movi​​es =电影;        }        / *        *内getView（）方法，你能吹一个基于XML的布局和        *然后设置的基于Java对象该行对个人意见的内容。        * * /        @覆盖        公共查看getView（INT位置，查看convertView，父母的ViewGroup）{            查看rowView = convertView;            如果（rowView == NULL）{                //充气基于XML布局                LayoutInflater吹气=（LayoutInflater）context.getSystemService（Context.LAYOUT_INFLATER_SERVICE）;                rowView = inflater.inflate（R.layout.movi​​es_item，父母，假）;                //获取的ImageView                ImageView的movieThumbnail =（ImageView的）rowView.findViewById（R.id.movi​​es_item_thumbnail）;                //加载图片到ImageView的                Picasso.with（上下文）.load（movies.get（位置）.getThumbnail（））到（movieThumbnail）。                Log.v（填充，movies.get（位置）.getThumbnail（））;            }            返回rowView;        }        @覆盖        公众诠释的getCount（）{            返回super.getCount（）;        }        @覆盖        公众诠释为getPosition（电影项目）{            返回super.getPosition（项目）;        }    }MovieFragment.java公共类MoviesFragment扩展片段{    私人MovieArrayAdapter mMoviesAdapter;    公共MoviesFragment（）{    }    @覆盖    公共无效调用onStart（）{        super.onStart（）;        新FetchMoviesTask（）执行（）;    }    @覆盖    公共查看onCreateView（LayoutInflater充气器，容器的ViewGroup，                             捆绑savedInstanceState）{        查看rootView = inflater.inflate（R.layout.fragment_main，集装箱，FALSE）;        mMoviesAdapter =新MovieArrayAdapter（getActivity（），新的ArrayList＆LT;电影及GT;（））;        GridView控件moviesGridView =（GridView控件）rootView.findViewById（R.id.movi​​es_gridview）;        moviesGridView.setAdapter（mMoviesAdapter）;        返回rootView;    }    公共类FetchMoviesTask扩展的AsyncTask＆LT;弦乐，太虚，电影[]＆GT; {        最后弦乐LOG_TAG = this.getClass（）getSimpleName（）。        @覆盖        保护电影[] doInBackground（字符串... PARAMS）{            //检索大众电影JSON字符串            串moviesJsonString = getMoviesJsonString（）;            //解析JSON字符串来获得重要数据            尝试{                返回getPopularMoviesInfo（moviesJsonString）;            }赶上（JSONException E）{                Log.e（LOG_TAG，e.getMessage（），E）;            }            返回null;        }        @覆盖        保护无效onPostExecute（动画[]电影）{            如果（电影！= NULL）{                mMoviesAdapter.clear（）;                mMoviesAdapter.addAll（电影）;            }        }        / *                *此功能是从Web API获取热门电影JSON字符串                * * /        私人字符串getMoviesJsonString（）{            HttpURLConnection类的URLConnection = NULL;            的BufferedReader的BufferedReader = NULL;            字符串moviesJsonString = NULL;            尝试{                //设置的URI                最后弦乐MOVIES_BASE_URL =htt​​p://api.themoviedb.org/3/discover/movie？                最后弦乐SORT_PARAM =sort_by;                最后弦乐API_PARAM =API_KEY;                乌里moviesUri = Uri.parse（MOVIES_BASE_URL）.buildUpon（）                        .appendQueryParameter（SORT_PARAMpopularity.desc）                        .appendQueryParameter（API_PARAM，的getString（R.string.movi​​es_api））                        。建立（）;                //打开连接                网址URL =新的URL（moviesUri.toString（））;                URLConnection的=（HttpURLConnection类）url.openConnection（）;                urlConnection.setRequestMethod（GET）;                urlConnection.connect（）;                //读取输入流中的字符串                为InputStream的InputStream = urlConnection.getInputStream（）;                如果（InputStream的== NULL）{                    返回null;                }                的BufferedReader =新的BufferedReader（新的InputStreamReader（InputStream的））;                串线;                StringBuffer的缓冲区=新的StringBuffer（）;                而（（行= bufferedReader.readLine（））！= NULL）{                    buffer.append（行+\\ n）;                }                如果（buffer.length（）== 0）{                    //流是空的                    返回null;                }                moviesJsonString = buffer.toString（）;            }赶上（IOException异常五）{                Log.e（LOG_TAG，错误，E）;            } {最后                如果（URLConnection的！= NULL）{                    urlConnection.disconnect（）;                }                如果（的BufferedReader！= NULL）{                    尝试{                        bufferedReader.close（）;                    }赶上（IOException异常五）{                        Log.e（LOG_TAG，错误收盘流，E）;                    }                }            }            返回moviesJsonString;        }        / *        *此功能是解析JSON字符串来检索信息        * * /        民营电影[] getPopularMoviesInfo（字符串jsonString）抛出JSONException {            //缩略图的基本URL            最后弦乐THUMBNAIL_BASE_URL =htt​​p://image.tmdb.org/t/p/w185;            //属性名，我们感兴趣的是JSON字符串            最后弦乐M_RESULTS =成果;            最后弦乐M_THUMBNAIL =backdrop_path;            最后弦乐M_TITLE =ORIGINAL_TITLE;            最后弦乐M_ID =ID;            最后弦乐M_SYPNOSIS =概览;            最后弦乐M_USER_RATING =vote_average;            最后弦乐M_RELEASE_DATE =RELEASE_DATE;            //转换JSON字符串以JSON对象            JSONObject的moviesJsonObject =新的JSONObject（jsonString）;            //获取JSON数组            JSONArray moviesJsonArray = moviesJsonObject.getJSONArray（M_RESULTS）;            电影[] =电影新电影[moviesJsonArray.length（）];            的for（int i = 0; I＆LT; moviesJsonArray.length（）;我++）{                的JSONObject电影= moviesJsonArray.getJSONObject（ⅰ）;                电影由[i] =新电影（THUMBNAIL_BASE_URL + movie.getString（M_THUMBNAIL）                                    movie.getString（M_TITLE）                                    movie.getString（M_ID）                                    movie.getString（M_SYPNOSIS）                                    movie.getString（M_USER_RATING）                                    movie.getString（M_RELEASE_DATE））;                Log.v（电影，movie.getString（M_TITLE））;            }            回归电影;        }    }} 

有没有错误，但图像不加载。我一直在寻找在其他线程，但无法找到答案我的问题。非常感谢你。

[增订]更改了code：

  @覆盖    公共查看getView（INT位置，查看convertView，父母的ViewGroup）{        如果（convertView == NULL）{            //充气基于XML布局            LayoutInflater吹气=（LayoutInflater）context.getSystemService（Context.LAYOUT_INFLATER_SERVICE）;            convertView = inflater.inflate（R.layout.movi​​es_item，父母，假）;        }        //获取的ImageView        ImageView的movieThumbnail =（ImageView的）convertView.findViewById（R.id.movi​​es_item_thumbnail）;        //加载图片到ImageView的        Picasso.with（上下文）.load（movies.get（位置）.getThumbnail（））到（movieThumbnail）。        Log.v（填充，movies.get（位置）.getThumbnail（））;        返回convertView;    } 

解决方案

这些行：

  //获取的ImageViewImageView的movieThumbnail =（ImageView的）rowView.findViewById（R.id.movi​​es_item_thumbnail）; //加载图片到ImageView的 Picasso.with（上下文）.load（movies.get（位置）.getThumbnail（））到（movieThumbnail）。 

去外面的如果（rowView == NULL）{

您总是会得到只有一个空 convertView ，你必须调用两行，而你正在更新/填充你的 GridView控件。此刻你应该看到遍地常存第一张图像。请不要忘了上网权限添加到清单

I have been making a Movie App (project work for learning android on udacity btw). I encountered a few problems but resolved them by following threads such as these Unable to modify ArrayAdapter in ListView: UnsupportedOperationException

However, although my app does not crash, the images are not loading and I cannot figure out why. Here is my code:

Layout XMl files movies_item.xml

<?xml version="1.0" encoding="utf-8"?>
<ImageView xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:id = "@+id/movies_item_thumbnail"
    >
</ImageView>

fragment_main.xml

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"
    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context="com.example.cindy.popularmovies.MoviesFragment">

    <GridView
        android:id="@+id/movies_gridview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:numColumns="auto_fit"
        android:gravity="center"
        />

</FrameLayout>

MovieArrayAdapter.java

    public class MovieArrayAdapter extends ArrayAdapter<Movie> {
        private final Context context;
        private final List<Movie> movies;

        public MovieArrayAdapter(Context context,List<Movie> movies) {
            super(context,0,movies);
            this.context = context;
            this.movies = movies;
        }

        /*
        * Within the getView() method you would inflate an XML based layout and
        * then set the content of the individual views based on the Java object for this row.
        * */

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

            View rowView = convertView;
            if(rowView == null) {
                //Inflate the XML based Layout
                LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
                rowView = inflater.inflate(R.layout.movies_item, parent, false);

                //Get the ImageView
                ImageView movieThumbnail = (ImageView) rowView.findViewById(R.id.movies_item_thumbnail);


                //Load Image into the ImageView
                Picasso.with(context).load(movies.get(position).getThumbnail()).into(movieThumbnail);

                Log.v("Populating", movies.get(position).getThumbnail());
            }
            return rowView;
        }

        @Override
        public int getCount() {
            return super.getCount();
        }

        @Override
        public int getPosition(Movie item) {
            return super.getPosition(item);
        }
    }


MovieFragment.java

public class MoviesFragment extends Fragment {

    private MovieArrayAdapter mMoviesAdapter;

    public MoviesFragment() {
    }

    @Override
    public void onStart() {
        super.onStart();
        new FetchMoviesTask().execute();
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);

        mMoviesAdapter = new MovieArrayAdapter(getActivity(),new ArrayList<Movie>());

        GridView moviesGridView = (GridView) rootView.findViewById(R.id.movies_gridview);
        moviesGridView.setAdapter(mMoviesAdapter);

        return rootView;
    }

    public class FetchMoviesTask extends AsyncTask<String,Void,Movie[]> {

        final String LOG_TAG = this.getClass().getSimpleName();

        @Override
        protected Movie[] doInBackground(String...params) {

            //Retrieve the Popular Movies Json String
            String moviesJsonString = getMoviesJsonString();

            //Parse the Json String to get important data
            try {
                return getPopularMoviesInfo(moviesJsonString);
            } catch(JSONException e) {
                Log.e(LOG_TAG,e.getMessage(),e);
            }
            return null;
        }

        @Override
        protected void onPostExecute(Movie[] movies) {
            if(movies != null) {
                mMoviesAdapter.clear();
                mMoviesAdapter.addAll(movies);
            }
        }

        /*
                * This Function is to retrieve the Popular movies Json String from a WEB API
                * */
        private String getMoviesJsonString() {
            HttpURLConnection urlConnection = null;
            BufferedReader bufferedReader = null;
            String moviesJsonString = null;

            try {

                //Set up the URI
                final String MOVIES_BASE_URL = "http://api.themoviedb.org/3/discover/movie?";
                final String SORT_PARAM = "sort_by";
                final String API_PARAM ="api_key";

                Uri moviesUri = Uri.parse(MOVIES_BASE_URL).buildUpon()
                        .appendQueryParameter(SORT_PARAM, "popularity.desc")
                        .appendQueryParameter(API_PARAM,getString(R.string.movies_api))
                        .build();

                //Open the connection
                URL url = new URL(moviesUri.toString());
                urlConnection = (HttpURLConnection)url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();

                //Read the input stream into a string
                InputStream inputStream = urlConnection.getInputStream();
                if(inputStream == null) {
                    return null;
                }

                bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

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

                if(buffer.length() == 0){
                    //Stream was empty
                    return null;
                }

                moviesJsonString = buffer.toString();

            }catch(IOException e) {
                Log.e(LOG_TAG,"Error",e);
            } finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if(bufferedReader != null) {
                    try {
                        bufferedReader.close();
                    } catch(IOException e) {
                        Log.e(LOG_TAG, "Error closing stream", e);
                    }
                }
            }

            return moviesJsonString;
        }

        /*
        * This function is to parse the JSON String to retrieve info
        * */
        private Movie[] getPopularMoviesInfo(String jsonString) throws JSONException{

            //Base URL of thumbnail
            final String THUMBNAIL_BASE_URL = " http://image.tmdb.org/t/p/w185";

            //The attribute names we are interested in the JSON String
            final String M_RESULTS = "results";
            final String M_THUMBNAIL = "backdrop_path";
            final String M_TITLE = "original_title";
            final String M_ID = "id";
            final String M_SYPNOSIS = "overview";
            final String M_USER_RATING = "vote_average";
            final String M_RELEASE_DATE = "release_date";


            //Convert Json String to Json Object
            JSONObject moviesJsonObject = new JSONObject(jsonString);

            //Get the Json Array
            JSONArray moviesJsonArray = moviesJsonObject.getJSONArray(M_RESULTS);

            Movie[] movies = new Movie[moviesJsonArray.length()];
            for(int i=0;i<moviesJsonArray.length();i++) {
                JSONObject movie = moviesJsonArray.getJSONObject(i);

                movies[i] = new Movie(THUMBNAIL_BASE_URL + movie.getString(M_THUMBNAIL),
                                    movie.getString(M_TITLE),
                                    movie.getString(M_ID),
                                    movie.getString(M_SYPNOSIS),
                                    movie.getString(M_USER_RATING),
                                    movie.getString(M_RELEASE_DATE));

                Log.v("Movie",movie.getString(M_TITLE));
            }

            return movies;

        }
    }
}

There is no error, but the images are not loading. I have been looking in other threads, but cannot find the answer to my problem. Thank you very much.

[UPDATED] Changed the code according to discussion below:

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

        if(convertView == null) {
            //Inflate the XML based Layout
            LayoutInflater inflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            convertView = inflater.inflate(R.layout.movies_item, parent, false);
        }

        //Get the ImageView
        ImageView movieThumbnail = (ImageView) convertView.findViewById(R.id.movies_item_thumbnail);

        //Load Image into the ImageView
        Picasso.with(context).load(movies.get(position).getThumbnail()).into(movieThumbnail);

        Log.v("Populating", movies.get(position).getThumbnail());

        return convertView;
    }

those line:

//Get the ImageView
ImageView movieThumbnail = (ImageView) rowView.findViewById(R.id.movies_item_thumbnail);

 //Load Image into the ImageView
 Picasso.with(context).load(movies.get(position).getThumbnail()).into(movieThumbnail);

go outside the if(rowView == null) {

You will always get only one null convertView, and you have to call that two lines while you are updating/populating your GridView . At the moment you should see alway the first image over and over. Please don't forget to add the Internet permission to the manifest