无法在 FragmentActivity 中获取 GridView

Question

当我在 Fragment 中实现 GridView 而不是 MainActivity class 并且在运行我的 phone 上的应用程序之后，屏幕是空白的。该应用程序从服务器正确获取数据，但未在移动屏幕上显示任何内容。

这是我的 MainActivityFragment class :

public class MainActivityFragment extends Fragment {

private GridView gridView;
private GridViewAdapter gridAdapter;
private ArrayList<ImageItem> data;
public MainActivityFragment() {
}

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

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

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

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

    data = new ArrayList<>();
    gridView = (GridView) rootView.findViewById(R.id.gridView);
    gridAdapter = new GridViewAdapter(getActivity(), R.layout.grid_poster, data);
    gridView.setAdapter(gridAdapter);
    return super.onCreateView(inflater, container, savedInstanceState);
}

@Override
public void onStart() {
    super.onStart();
    FetchPosterTask posterTask = new FetchPosterTask();
    posterTask.execute();
}

public class FetchPosterTask extends AsyncTask<Void, Void, Integer> {

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

    private Integer parseResult(String result)
            throws JSONException{

            JSONObject response = new JSONObject(result);
            JSONArray movies = response.getJSONArray("results");
            ImageItem item = new ImageItem();
            for (int i = 0; i < movies.length(); i++) {
                JSONObject movie = movies.optJSONObject(i);

                item = new ImageItem();
                String posterPath = movie.getString("poster_path");
                Uri.Builder builder = new Uri.Builder();
                builder.scheme("https")
                        .authority("image.tmdb.org")
                        .appendPath("t")
                        .appendPath("p")
                        .appendPath("w185");
                String poster  = builder.toString()+posterPath;
                item.setImage(poster);
                Log.v(LOG_TAG, "poster_path " + poster);
                }
                data.add(item);
             return 1;
    }

    @Override
    protected Integer doInBackground(Void... params) {

        Integer result = 0;
        HttpURLConnection urlConnection = null;
        String moviesJasonStr = null;
        String sort_by = "popularity.desc";
        BufferedReader reader = null;
        try {
            final String baseUrl = "http://api.themoviedb.org/3/discover/movie?";
            final String QUERY_PARAM = "sort_by";
            final String APPID_PARAM = "api_key";
            Uri builtUri = Uri.parse(baseUrl).buildUpon()
                    .appendQueryParameter(QUERY_PARAM, sort_by)
                    .appendQueryParameter(APPID_PARAM, BuildConfig.OPEN_MOVIES_API_KEY)
                    .build();
            URL url = new URL(builtUri.toString());
            urlConnection = (HttpURLConnection) url.openConnection();
            urlConnection.setRequestMethod("GET");
            urlConnection.connect();

            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) {
                // Since it's JSON, adding a newline isn't necessary (it won't affect parsing)
                // But it does make debugging a *lot* easier if you print out the completed
                // buffer for debugging.
                buffer.append(line + "\n");
            }

            if (buffer.length() == 0) {
                // Stream was empty.  No point in parsing.
                return null;
            }
            moviesJasonStr = buffer.toString();

            Log.v(LOG_TAG, "moviesJasonStr: " + moviesJasonStr);


        } catch (IOException e) {
            Log.e(LOG_TAG, "Error ", e);
            // If the code didn't successfully get the weather data, there's no point in attemping
            // to parse it.
            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 parseResult(moviesJasonStr);
        } catch (JSONException e) {
            Log.e(LOG_TAG, e.getMessage(), e);
            e.printStackTrace();
        }
        return null;
    }

    @Override
    protected void onPostExecute(Integer integer) {
        Log.v(LOG_TAG, "result_integer: " + integer);
        if (integer == 1) {
            gridAdapter.setGridData(data);
        } else {
            Toast.makeText(getActivity(), "Failed to fetch data!", Toast.LENGTH_SHORT).show();
        }
    }
}

}

这是我的 GridViewAdapter class :

public class GridViewAdapter extends ArrayAdapter<ImageItem> {

private Context context;
private int layoutResourceId;
private ArrayList<ImageItem> data = new ArrayList<ImageItem>();

public GridViewAdapter(Context context, int layoutResourceId, ArrayList<ImageItem> data) {
    super(context, layoutResourceId, data);
    this.layoutResourceId = layoutResourceId;
    this.context = context;
    this.data = data;
}
/**
 * Updates grid data and refresh grid items.
 * @param data
 */
public void setGridData(ArrayList<ImageItem> data) {
this.data = data;
    notifyDataSetChanged();
}



@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View row = convertView;
    ViewHolder holder;

    if (row == null) {
        LayoutInflater inflater = ((Activity) context).getLayoutInflater();
        row = inflater.inflate(layoutResourceId, parent, false);
        holder = new ViewHolder();
        holder.image = (ImageView) row.findViewById(R.id.image);
        row.setTag(holder);
    } else {
        holder = (ViewHolder) row.getTag();
    }


    ImageItem item = data.get(position);
    //holder.image.setImageBitmap(item.getImage());
    Picasso.with(context).load(item.getImage()).into(holder.image);
    return row;
}

static class ViewHolder {
    ImageView image;
}

}

这是我的 fragment_main.xml 文件：

<RelativeLayout 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:background="#f0f0f0"
tools:context = ".MainActivityFragment">

<GridView
    android:id="@+id/gridView"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:layout_margin="5dp"
    android:columnWidth="100dp"
    android:drawSelectorOnTop="true"
    android:gravity="center"
    android:numColumns="auto_fit"
    android:stretchMode="columnWidth"
    android:verticalSpacing="5dp"
    android:focusable="true"
    android:clickable="true"/>
   </RelativeLayout>

Answer 1

首先returnrootView在onCreate

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

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

    data = new ArrayList<>();
    gridView = (GridView) rootView.findViewById(R.id.gridView);
    gridAdapter = new GridViewAdapter(getActivity(), R.layout.grid_poster, data);
    gridView.setAdapter(gridAdapter);
    return rootView;
}

如果它不起作用，则在 onPostexecute

中设置适配器

Answer 2

你只有fragment，但是fragment需要activity来承载，你可以把这段代码public class MainActivityFragment extends Fragment改成public class MainActivityFragment extends FragmentActivity

无法在 FragmentActivity 中获取 GridView

Unable to get GridView in FragmentActivity

android

gridview

android-fragmentactivity