[编辑：能够通过在片段加载时将空白图像传递给列表数组来解决这个问题]
我正在开发一个应用程序，用于刷新网格视图，从API中动态获取数据。我的gridview不会在加载时重新加载。点击其他选项（如排序）或仅更改应用中的方向即可进行刷新。如何让它在加载时刷新。我试过从onStart（），onCreate（）和onCreateView（）调用刷新函数，但是它没有工作。
Github：https://github.com/abhrajitmukherjee/PopularMovies
主要代码：
public class MainActivityFragment extends Fragment {
private ImageAdapter mImageAdapter;
public ArrayList<String[]> mThumbIds;
private GridView gridview;
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_main, menu);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
Log.v("Initiate","Starts here-------------------");
updateMovieThumbs(getString(R.string.base_uri_popular));
gridview = (GridView) getActivity().findViewById(R.id.gridview);
mImageAdapter = new ImageAdapter(getActivity());
gridview.setAdapter(mImageAdapter);
updateMovieThumbs(getString(R.string.base_uri_popular));
gridview.setOnItemClickListener(new AdapterView.OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View v,
int position, long id) {
Intent intent = new Intent(getActivity(), MovieDetailsActivity.class)
.putExtra(getString(R.string.intent_poster_path), mThumbIds.get(position)[0])
.putExtra(getString(R.string.intent_title),mThumbIds.get(position)[1])
.putExtra(getString(R.string.intent_overview),mThumbIds.get(position)[2])
.putExtra(getString(R.string.intent_vote_avg),mThumbIds.get(position)[3])
.putExtra(getString(R.string.intent_release_date),mThumbIds.get(position)[4]);
startActivity(intent);
}
});
}
@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_toprated) {
updateMovieThumbs(getString(R.string.base_uri_toprated));
} else if (id == R.id.action_popular) {
updateMovieThumbs(getString(R.string.base_uri_popular));
}
return true;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View v = inflater.inflate(R.layout.fragment_main, container, false);
mThumbIds = new ArrayList<String[]>();
return v;
}
@Override
public void onStart() {
super.onStart();
}
private void updateMovieThumbs(String sortType) {
FetchMovieDatabase movieTask = new FetchMovieDatabase();
movieTask.execute(sortType);
Log.v("getCount", "Get Main count=" + Integer.toString(mThumbIds.size()));
}
public class FetchMovieDatabase extends AsyncTask<String, Void, ArrayList<String[]>> {
private final String LOG_TAG = FetchMovieDatabase.class.getSimpleName();
private ArrayList<String[]> getMovieDataJson(String movieJsonStr)
throws JSONException {
final String RESULTS = "results";
final String ORIGINAL_TITLE="original_title";
final String POSTER="poster_path";
final String OVERVIEW="overview";
final String VOTES="vote_average";
final String RELEASE="release_date";
ArrayList<String[]> newThumbids=new ArrayList<String[]>();
JSONObject movieJson = new JSONObject(movieJsonStr);
JSONArray movieArray = movieJson.getJSONArray(RESULTS);
for (int i = 0; i < movieArray.length(); i++) {
JSONObject results = movieArray.getJSONObject(i);
String posterPath = getString(R.string.api_image_base_path)+results.getString(POSTER);
String title=results.getString(ORIGINAL_TITLE);
String overview=results.getString(OVERVIEW);
String voteAvg=results.getString(VOTES);
String releaseDate=results.getString(RELEASE);
String[] outputAttr={posterPath,title,overview,voteAvg,releaseDate};
Log.v(LOG_TAG, posterPath);
newThumbids.add(outputAttr);
Log.v(LOG_TAG, Integer.toString(newThumbids.size()));
}
return newThumbids;
}
@Override
protected ArrayList<String[]> doInBackground(String... params) {
if (params.length == 0) {
return null;
}
HttpURLConnection urlConnection = null;
BufferedReader reader = null;
String movieJsonStr = null;
try {
final String BASE_URL = params[0];
final String API_KEY = "api_key";
Uri builtUri = Uri.parse(BASE_URL).buildUpon()
.appendQueryParameter(API_KEY, BuildConfig.MOVIES_API_KEY)
.build();
URL url = new URL(builtUri.toString());
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
urlConnection.connect();
// Read the input stream into a String
InputStream inputStream = urlConnection.getInputStream();
StringBuffer buffer = new StringBuffer();
if (inputStream == null) {
// Nothing to do.
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();
} catch (IOException 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);
}
}
}
try {
return getMovieDataJson(movieJsonStr);
} catch (JSONException e) {
Log.e(LOG_TAG, e.getMessage(), e);
e.printStackTrace();
}
return null;
}
@Override
protected void onPostExecute(ArrayList<String[]> result) {
if (result != null) {
if (mThumbIds.size()>0){
mThumbIds.clear();
}
mThumbIds = (ArrayList<String[]>) result.clone();
Log.v(LOG_TAG, "Postexecute count:"+Integer.toString( mThumbIds.size()));
mImageAdapter.notifyDataSetChanged();
}
}
}
public class ImageAdapter extends BaseAdapter {
private Context mContext;
public ImageAdapter(Context c) {
mContext = c;
}
public int getCount() {
Log.v("getCount", "Get Count=" + Integer.toString(mThumbIds.size()));
// return 5;
return mThumbIds.size();
}
public Object getItem(int position) {
return null;
}
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.setAdjustViewBounds(true);
imageView.setScaleType(ImageView.ScaleType.FIT_XY);
} else {
imageView = (ImageView) convertView;
}
Picasso.with(getActivity()).load(mThumbIds.get(position)[0]).into(imageView);
return imageView;
}
}
}