Question

我使用Two Fragment创建了一个Android应用程序， MainFragment - ＆gt;的 WebviewFragment 即可。 MainFragment是GridView，它从 Json 链接获取网格项。当我通过按后退按钮从 WebviewFragment 导航回 MainFragment 时，Gridview会再次获取数据。对此有什么解决方案吗？

MainFragment

public class MainFragment extends Fragment {


    // Log tag

    private static final String TAG = MainActivity.class.getSimpleName();

    // Movies json url

    private static final String url = "http://api....";
    private ProgressDialog pDialog;
    private List<Movie> movieList;
    private GridView gridView;
    private TextView scrollingtext;
    private AppController appController;





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

        movieList  = new ArrayList<Movie>();

        View view = inflater.inflate(R.layout.main_fragment, container, false);
        scrollingtext = (TextView) view.findViewById(R.id.scroll_annouc);
        scrollingtext.setSelected(true);
        gridView = (GridView) view.findViewById(R.id.Grid_view);
        final CustomListAdapter adapter = new CustomListAdapter(getActivity(), movieList);
        gridView.setAdapter(adapter);



            gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> parent, View view, int position, long id) {



                    Bundle bundle = new Bundle();
                    bundle.putString("LINK","http://www.kalerkantho.com/");

                    Fragment newFragment = new WebviewFragment();
                    FragmentTransaction transaction = getFragmentManager().beginTransaction();
                    newFragment.setArguments(bundle);

                    transaction.replace(R.id.main_fragment_container, newFragment);
                    transaction.addToBackStack(null);
                    transaction.commit();


                }
            });


        pDialog = new ProgressDialog(getActivity());
        // Showing progress dialog before making http request
        pDialog.setMessage(" Loading ...");
        pDialog.show();

        // Creating volley request obj
        JsonArrayRequest movieReq = new JsonArrayRequest(url, new Response.Listener<JSONArray>() {
            @Override
            public void onResponse(JSONArray response) {
                Log.d(TAG, response.toString());
                hidePDialog();

                // Parsing json
                for (int i = 0; i < response.length(); i++) {
                    try {

                        JSONObject obj = response.getJSONObject(i);
                        Movie movie = new Movie();
                        movie.setTitle(obj.getString("title"));
                        movie.setThumbnailUrl(obj.getString("image"));


                        // adding movie to movies array
                        movieList.add(movie);

                    } catch (JSONException e) {
                        e.printStackTrace();
                    }

                }

                // notifying list adapter about data changes
                // so that it renders the list view with updated data
               adapter.notifyDataSetChanged();
            }
        }, new Response.ErrorListener() {
            @Override
            public void onErrorResponse(VolleyError error) {
                VolleyLog.d(TAG, "Error: " + error.getMessage());
                hidePDialog();

            }
        });



        // Adding request to request queue
        appController.getInstance().addToRequestQueue(movieReq);

        return view;
    }



    @Override
    public void onDestroy() {
        super.onDestroy();
        hidePDialog();
    }

    private void hidePDialog() {
        if (pDialog != null) {
            pDialog.dismiss();
            pDialog = null;
        }
    }

WebviewFragment

public class WebviewFragment extends Fragment {


    WebView webView;
    String newslink;

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

        View view = inflater.inflate(R.layout.fragment_webview,container,false);

        newslink = getArguments().getString("LINK");

        webView = (WebView) view.findViewById(R.id.webView);
        webView.loadUrl(newslink);
        webView.getSettings().setJavaScriptEnabled(true);


        return view;
    }
}


     }

Answer 1

您可以使用SharedPreferences保存一个标记，表明您是否已加载数据，然后在片段之间切换时检查此标志。

如果您的标志处于活动状态，您还应该将数据保存在SharedPreferences中，或者维护内部数据库并加载该数据，而不是再次转换JSON。

Answer 2

您可以使用Fragment完成此操作。将主内容父布局设置为Framelayout，并在使用命令fragment.add按下按钮或所需内容时使Webview膨胀，并在backpress时使用fragment.remove。

Answer 3

当你view时，

膨胀null不会popback。所以只需在替换Fragment

时夸大视图

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


    if (view ==null){//null means fragment replaced  and not null means popbacked 
     View view = inflater.inflate(R.layout.main_fragment, container, false);
     init();
   }

    return view;
}

private void init() {
    scrollingtext = (TextView) view.findViewById(R.id.scroll_annouc);
    scrollingtext.setSelected(true);
    gridView = (GridView) view.findViewById(R.id.Grid_view);
    final CustomListAdapter adapter = new CustomListAdapter(getActivity(), movieList);
    gridView.setAdapter(adapter);


    gridView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
        @Override
        public void onItemClick(AdapterView<?> parent, View view, int position, long id) {


            Bundle bundle = new Bundle();
            bundle.putString("LINK", "http://www.kalerkantho.com/");

            Fragment newFragment = new WebviewFragment();
            FragmentTransaction transaction = getFragmentManager().beginTransaction();
            newFragment.setArguments(bundle);

            transaction.replace(R.id.main_fragment_container, newFragment);
            transaction.addToBackStack(null);
            transaction.commit();


        }
    });
    pDialog = new ProgressDialog(getActivity());
    // Showing progress dialog before making http request
    pDialog.setMessage(" Loading ...");
    pDialog.show();

    // Creating volley request obj
    JsonArrayRequest movieReq = new JsonArrayRequest(url, new Response.Listener<JSONArray>() {
        @Override
        public void onResponse(JSONArray response) {
            Log.d(TAG, response.toString());
            hidePDialog();

            // Parsing json
            for (int i = 0; i < response.length(); i++) {
                try {

                    JSONObject obj = response.getJSONObject(i);
                    Movie movie = new Movie();
                    movie.setTitle(obj.getString("title"));
                    movie.setThumbnailUrl(obj.getString("image"));


                    // adding movie to movies array
                    movieList.add(movie);

                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
            // notifying list adapter about data changes
            // so that it renders the list view with updated data
            adapter.notifyDataSetChanged();
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            VolleyLog.d(TAG, "Error: " + error.getMessage());
            hidePDialog();

        }
    });
    // Adding request to request queue
    appController.getInstance().addToRequestQueue(movieReq);
}

Answer 4

您还可以在setRetainInstance(true);中使用MainFragment来保持实例状态。

希望这有帮助。

当我按下后退按钮时如何阻止GridView再次加载？

4 个答案: