Question

我想问一下，我有2个班级：

   1. an activity class (to get data from json)
   2. a fragment class (not to do something)

我希望通过片段类从活动的json获取数据。可以在一个类中结合Activity和Fragment吗？怎么办？

我在Fragment类中组合了活动和片段，我使用了GridView来获取数据和显示 JSON，在此片段中执行AsyncTask

这是我在25/10更新后的代码：

public class FeedBackFragment extends Fragment {

ProgressDialog pDialog;
JSONParser jsonParser = new JSONParser();

MyAdapter adapter;
JSONArray manufacturers = null;

// manufacturers JSON url
private static final String URL_MANUFACTURERS ="MYURL";

public FeedBackFragment() {
    // Required empty public constructor
}

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    View view = inflater.inflate(R.layout.feedback_gridview_manufacturer, container, false);

    GridView gridView = (GridView) view.findViewById(R.id.gridview);
    gridView.setAdapter(new MyAdapter(getActivity(), manufacturersList));

    gridView.setOnItemClickListener(new android.widget.AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> arg0, View view, int arg2, long arg3) {
            // on selecting a single manufacturer
            // CategoryCarActivity will be launched to show category car inside the manufacturer
            Intent i = new Intent(getActivity(), CategoryCarActivity.class);

            // send manufacturer id to activity to get list of cars under that manufacturer
            String manufacturer_id = ((TextView) view.findViewById(R.id.manufacturer_id)).getText().toString();
            i.putExtra("manufacturer_id", manufacturer_id);

            startActivity(i);
        }
    });

    return view;
}

@Override
public void onActivityCreated(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onActivityCreated(savedInstanceState);

    // manufacturersList = new ArrayList<>();
    new LoadAllManufacturers().execute();
}


class LoadAllManufacturers extends AsyncTask<String, String, String> {
    /**
     * Before starting background thread Show Progress Dialog
     * */
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(getActivity());
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(false);
        pDialog.show();
    }

    /**
     * After completing background task Dismiss the progress dialog
     * **/
    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);

        adapter.notifyDataSetChanged();
        // dismiss the dialog after getting all manufacturers
        if (pDialog.isShowing())
            pDialog.dismiss();
    }
}

private class MyAdapter extends BaseAdapter
{

    // List<POJOManufacturer> listData = null;
    LayoutInflater inflater;
    Context context;

    public MyAdapter(Context context, ArrayList<HashMap<String, String>> arrayList)
    {
        // this.context = context;
        this.manufacturersList = arrayList;
        inflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        if (manufacturersList != null)
            return manufacturersList.size();
        return 0;
    }

    @Override
    public Object getItem(int i)
    {
        if (manufacturersList != null)
            return manufacturersList.get(i);
        return null;
    }

    @Override
    public long getItemId(int i)
    {
        if (manufacturersList != null)
            return manufacturersList.get(i).hashCode();
        return 0;
    }

    @Override
    public View getView(int i, View convertView, ViewGroup viewGroup)
    {
        ViewHolder holder;
        if (convertView == null)
        {
            convertView = inflater.inflate(R.layout.gridview_item, null);
            holder = new ViewHolder();
            holder.name = (TextView) convertView.findViewById(R.id.text);
            holder.iconName = (ImageView) convertView.findViewById(R.id.picture);

            convertView.setTag(holder);
        }
        else {

            holder = (ViewHolder) convertView.getTag();
        }           
        holder.name.setText(this.manufacturersList.get(i).getClass().getName());
        // holder.iconName.setImageResource(this.manufacturersList.get(i).image);

        return convertView;
    }

    public class ViewHolder
    {
        TextView name;
        ImageView iconName;
    }        
   }
 }

我已更新并添加：manufacturerList = new ArrayList＆lt;＆gt ;.一切似乎都更好，并且在 getView（） 方法中遇到了一些问题，我试过，它只在gridview中显示7个空项目，而不显示内容和图像

那么如何将适配器中的数据填充到Gridview中？

Answer 1

类ManufacturerFragment中的构造函数ManufacturerFragment不能应用于给定类型;

gridView.setAdapter()使用适配器，而不是Fragment

并且new ManufacturerFragment()不接受Context。

我不确定你为什么认为你需要在你已经进入的Fragment类中创建new ManufacturerFragment。你的意思是gridView.setAdapter(new MyAdapter(getActivity()))吗？

此外，您的manufacturersList需要加载到该适配器中，因此您需要弄明白。

您需要在大多数地方使用getActivity()代替getActivity().getApplicationContext()。

然后，您应该只调用new LoadAllManufacturers().execute();或onCreateView中的onActivityCreated，而不是两者。否则，您正在运行两个AsyncTasks。

然后，onPostExecute已在UI线程上运行，无需使用getActivity().runOnUiThread(new Runnable() {...

一旦弄清楚如何将ArrayList放入Adapter类，你需要在adapter.notifyDataSetChanged()内调用onPostExecute告诉适配器刷新数据，从而更新GridView以显示数据。

将Activity和fragment组合成一个android类

1 个答案: