在android的图像适配器中本地保存图像

Question

这是一个关于安卓应用中图像保存的问题。 我正在尝试制作一个 udacity 项目的流行电影应用程序。链接 - https://docs.google.com/document/d/1gtXUu1nzLGWrGfVCD6tEA0YHoYA9UNyT2yByqjJemp8/pub?embedded=true

我在 ImageAdapter 中有用于图像下载的毕加索库--
这是我的 ImageAdapter 代码 -

package jindal5.mayank.popular_movies_14ce10032_gsc;

public class ImageAdapter extends BaseAdapter {
    private String drawablePrefix;
    private Context mContext;
    private ArrayList<String> mThumbUris;
    private ArrayList<String> mov_id_arr;
    private ArrayList<String> mov_tit_arr;

    public ImageAdapter(Context c) {
        mContext = c;
        String packName=mContext.getPackageName();
        drawablePrefix="android.resource://" +packName+ "/";
        ArrayList<String> mov_id_arr =new ArrayList<>();
        ArrayList<String> mov_tit_arr=new ArrayList<>();
        mov_tit_arr.add("asdf");
        mov_tit_arr.add("asdf");
        mov_tit_arr.add("asdf");
        mov_tit_arr.add("asdf");
        mov_tit_arr.add("asdf");
        mov_tit_arr.add("asdf");

        ArrayList<String> uriPaths=new ArrayList<>();// place your drawables.

        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);


        mThumbUris=uriPaths;
    }

    public int getCount() {
        return mThumbUris.size();
    }

    public Object getItem(int position) {
        return mThumbUris.get(position);
    }

    public long getItemId(int position) {
        return 0;
    }

    // create a new ImageView for each item referenced by the Adapter
    public View getView(int position, View convertView, ViewGroup parent) {
        ImageView imageView;
        if (convertView == null) {
            // if it's not recycled, initialize some attributes
            imageView = new ImageView(mContext);
           // imageView.setLayoutParams(new GridView.LayoutParams(85, 85));
           // imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
           // imageView.setPadding(8, 8, 8, 8);
        } else {
            imageView = (ImageView) convertView;
        }
        Uri imgUri=Uri.parse(mThumbUris.get(position));

        Picasso.with(mContext)
                .load(imgUri)
                .placeholder(R.drawable.sample_0)
               .centerCrop()
                .resize(400,400)
                .into(imageView);
       imageView.setImageResource(mThumbIds[position]);
       // imageView.setAdjustViewBounds(true);
        return imageView;
    }

    public ArrayList<String> getUriList(){
        return mThumbUris;
    }
    public ArrayList<String> getidlist(){
        return mov_id_arr;
    }
    public ArrayList<String> gettitlist(){
        return mov_tit_arr;
    }

    // references to our images
    private Integer[] mThumbIds = {
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7,
            R.drawable.sample_0, R.drawable.sample_1,
            R.drawable.sample_2, R.drawable.sample_3,
            R.drawable.sample_4, R.drawable.sample_5,
            R.drawable.sample_6, R.drawable.sample_7
    };
}

现在我有两个问题 -

1. 当我从另一个活动返回主活动时，会显示本地图像，而不是之前下载的图像。
2. 当我关闭我的应用程序并再次打开时，我看到本地图像出现，而不是上次下载的图像。有人告诉您必须使用文件或内容提供程序将图像下载到本地内存后保存。但我不知道该怎么做？？ .

3.当我改变我的设备方向时，我遇到了同样的问题。

这是我的主要活动片段-

package jindal5.mayank.popular_movies_14ce10032_gsc;

/**
 * A placeholder fragment containing a simple view.
 */
public class MainActivityFragment extends Fragment {
    public ImageAdapter imag_adap;
    public String movieJsonStr;
    public ArrayList<String > tit_arr = new ArrayList<String>();
    public ArrayList<String > rel_dat_arr = new ArrayList<String>();
    public ArrayList<String > url1_arr = new ArrayList<String>();
    public ArrayList<String > over_arr = new ArrayList<String>();
    public ArrayList<String > id_arr = new ArrayList<String>();
    public String put_ext_tit;
    public String rel_date_ext;
 public  String url_for_pos_ex;
    public String over_ex;
    public String id_ex;
    public MainActivityFragment() {
    }
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        // Add this line in order for this fragment to handle menu events.
        setHasOptionsMenu(true);
    }

    @Override
    public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) {
        inflater.inflate(R.menu.menu_fragment, menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_refresh) {
            //SharedPreferences share = PreferenceManager.getDefaultSharedPreferences();
          //  String order = share.getString()
            getimage imageTask = new getimage();
            imageTask.execute("popularity.desc");
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
       View rootview = inflater.inflate(R.layout.fragment_main, container, false);
        GridView grid = (GridView) rootview.findViewById(R.id.gridView);
        imag_adap = new ImageAdapter(getActivity());
        grid.setAdapter(imag_adap);

        grid.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                String[] tit1 = tit_arr.toArray(new String[tit_arr.size()]);
                String[] rel_date = rel_dat_arr.toArray(new String[rel_dat_arr.size()]);
                String[] url_for_pos = url1_arr.toArray(new String[url1_arr.size()]);
                String[] over = url1_arr.toArray(new String[over_arr.size()]);
                String[] id = id_arr.toArray(new String[over_arr.size()]);
               // Log.v("mayank",tit1[3]);
                try{
                    put_ext_tit = tit1[i];
                    rel_date_ext = rel_date[i];
                    url_for_pos_ex = url_for_pos[i];
                    over_ex = over[i];
                    id_ex =id[i];
                    Intent intent = new Intent(getActivity(),det_mov.class);
                    //.putExtra(Intent.EXTRA_TEXT,put_ext_tit);
                    Bundle extras = new Bundle();
                    extras.putString("title",put_ext_tit);
                    extras.putString("rel_date",rel_date_ext);
                    extras.putString("url_pos",url_for_pos_ex);
                    extras.putString("over_ex",over_ex);
                    extras.putString("id_ex", id_ex);
                    extras.putInt("posit",i);
                    intent.putExtras(extras);
                    startActivity(intent);
                }
                catch (ArrayIndexOutOfBoundsException p){
                    Log.e("mayank","reg",p);
                }
            }
        });

        return rootview;
    }

    public class getimage extends AsyncTask<String, String, String[]> {
        ConnectivityManager conMgr = (ConnectivityManager) getActivity().getSystemService(Context.CONNECTIVITY_SERVICE);


        private final String LOG_TAG = getimage.class.getSimpleName();
        public int count;
        String[] pos_path;
        String[]  mov_id;
        String[] tit;
        String[] rev;
        String[] rel_dat;
        String[] url1;
        String[] over;
        String[] id;
        public ImageAdapter getad(){
            return imag_adap;
        }


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

            BufferedReader reader = null;
            try {
                final String movie_url_str = "http://api.themoviedb.org/3/discover/movie?sort_by="+ params[0] +"&api_key=8d7a48043ba1d3348181e2b6615cedc7";
                URL movie_url = new URL(movie_url_str);
                urlConnection = (HttpURLConnection) movie_url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.connect();
                InputStream inputStream = urlConnection.getInputStream();
                StringBuffer buffer = new StringBuffer();
                if (inputStream == null) {
                    return null;
                }
                reader = new BufferedReader(new InputStreamReader(inputStream));
                String line;
                while ((line = reader.readLine()) != null) {
                    buffer.append(line + "\n");
                }
                if (buffer.length() == 0) {
                    return null;
                }
               movieJsonStr = buffer.toString();

                JSONObject movieJson = new JSONObject(movieJsonStr);
                JSONArray movieJsonarray = movieJson.getJSONArray("results");
                 count = movieJsonarray.length();
                pos_path = new String[count];
                mov_id = new String[count];
                tit = new String[count];
                rev = new String[count];
                rel_dat = new String[count];
                url1 = new String[count];
                over = new String[count];
                id = new String[count];
                for(int i=0;i<count;i++){
                    JSONObject sin_movie = movieJsonarray.getJSONObject(i);
                    pos_path[i] = sin_movie.getString("poster_path");
                    over[i] = sin_movie.getString("overview");
                    Uri.Builder url_for_poster = new Uri.Builder();
                    String qw = "t";
                    String as = "p";
                    Uri.Builder url_build =  url_for_poster.scheme("http").authority("image.tmdb.org").appendPath(qw).appendPath(as).appendPath("w500").appendEncodedPath(pos_path[i]);
                     url1[i] = url_build.toString();

                   // mov_id[i] =  sin_movie.getString("id");
                   tit[i] = sin_movie.getString("title");
                    //rev[i] = sin_movie.getString("review");
                    rel_dat[i] = sin_movie.getString("release_date");
                    id[i] = sin_movie.getString("id");
                    publishProgress((String)(tit[i]),(String)(rel_dat[i]),(String)(url1[i]),(String)(over[i]),(String)(id[i]));
                    Log.v(LOG_TAG, "Forecast string: " + id[i]);

                }
            } catch (IOException | JSONException e) {
                Log.e(LOG_TAG, "Error ", e);
                return null;
            }
            finally {
                if (urlConnection != null) {
                    urlConnection.disconnect();
                }
                if (reader != null) {
                    try {
                        reader.close();
                    } catch (final IOException e) {
                        Log.e(LOG_TAG, "Error closing stream", e);
                    }
                }
            }
            return pos_path;
            }
        @Override
        protected void onProgressUpdate(String... values) {

                tit_arr.add(values[0]);
            rel_dat_arr.add(values[1]);
            url1_arr.add(values[2]);
            over_arr.add(values[3]);
            id_arr.add(values[4]);
        }

        @Override
        protected void onPostExecute(String[] result) {

            ArrayList<String> uriPaths = imag_adap.getUriList();
            uriPaths.clear();
           // ImageView[] im_vi = new ImageView[count];

            for(int j=0;j<count;j++) {

               String  pos_sin_path = pos_path[j];
                String id_mov = id[j];
                Uri.Builder url_for_poster = new Uri.Builder();
                Uri.Builder url_for_rev = new Uri.Builder();
                String qw = "t";
                String as = "p";
              Uri.Builder url_build =  url_for_poster.scheme("http").authority("image.tmdb.org").appendPath(qw).appendPath(as).appendPath("w500").appendEncodedPath(pos_sin_path);
                String url = url_build.toString();
                Uri.Builder url_build_rev = url_for_rev.scheme("http").encodedAuthority("api.themoviedb.org/3/movie").appendPath(id_mov).appendPath("reviews");
                uriPaths.add(url);
               // mov_title.add(tit[j]);
                //mov_id_arr.add(id);
             //   mov_tit_arr.add(title);
             // }
              //catch (UnsupportedEncodingException e){

              //}
                //url_build.clearQuery();

                //Picasso.with(getActivity()).load("http://image.tmdb.org/t/p/w185//nBNZadXqJSdt05SHLqgT0HuC5Gm.jpg").into(im_vi[j]);
                //imag_adap.getItem(j) = im_vi[j];\

            }
            imag_adap.notifyDataSetChanged();
        }
    }
}

寻求帮助，因为我是 android 新手。

Answer 1

当我关闭我的应用程序并再次打开时，我看到本地图像出现，而不是上次下载的图像。有人告诉您必须使用文件或内容提供程序将图像下载到本地内存后保存。但我不知道该怎么做？？ .

这是意料之中的，因为您的设备上的任何位置都没有照片。将图像保存在数据库 (SQLite) 中，如果您希望它在返回应用程序时保留并可用。或者您每次重新启动活动时加载它们，最好通过 AsyncTask。

要在 SQLite 数据库中存储图像，请查看 How to store(bitmap image) and retrieve image from sqlite database in android? 告诉您有关保存和检索图像的所有信息。

Answer 2

试试这个，

answer-1：

尝试将适配器初始化逻辑从onCreateView改为onCreate。 将这一行放在 onCreate 中。

imag_adap = new ImageAdapter(getActivity());

answer-2：

下载图像后，将该 uri 路径保存在数据库或文件或 sharedpreference 中。然后在创建适配器中检索该 uri。

ArrayList<String> uriPathsFromDb=getListOfUriFromDatabase();
if(uriPathsFromDb.size()==0){
ArrayList<String> uriPaths=new ArrayList<>();// place your drawables.

        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);
        uriPaths.add(drawablePrefix+ R.drawable.sample_0);

        mThumbUris=uriPaths;
}else{
   mThumbUris=uriPathsFromDb;
}