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问题描述
我创建了两个片段的Android应用程序， MainFragment - > WebviewFragment 。该MainFragment是其中的GridView从获取的的Json 链接网格项目。当我从导航回 WebviewFragment 为 MainFragment 按pressing后退按钮时，GridView再次获取数据。请问有什么办法解决这个？
MainFragment
公共类MainFragment扩展片段{
//日志标签 私有静态最后弦乐TAG = MainActivity.class.getSimpleName（）; //电影JSON网址 私有静态最终字符串URL =HTTP：// API ......;
私人ProgressDialog pDialog;
私人列表＆LT;电影及GT; movieList;
私人GridView控件GridView控件;
私人TextView的scrollingtext;
私人AppController的AppController的; @覆盖
公共查看onCreateView（LayoutInflater充气器，容器的ViewGroup，捆绑savedInstanceState）{ movieList =新的ArrayList＆LT;电影及GT;（）; 查看查看= inflater.inflate（R.layout.main_fragment，集装箱，FALSE）;
scrollingtext =（TextView中）view.findViewById（R.id.scroll_annouc）;
scrollingtext.setSelected（真）;
GridView控件=（GridView控件）view.findViewById（R.id.Grid_view）;
最后CustomListAdapter适配器=新CustomListAdapter（getActivity（），movieList）;
gridView.setAdapter（适配器）; gridView.setOnItemClickListener（新AdapterView.OnItemClickListener（）{
@覆盖
公共无效onItemClick（适配器视图＆LT;＆GT;母公司，观景，INT位置，长的id）{ 束束=新包（）;
bundle.putString（LINK，http://www.kalerkantho.com/）; 片段newFragment =新WebviewFragment（）;
FragmentTransaction交易= getFragmentManager（）调用BeginTransaction（）。
newFragment.setArguments（包）; transaction.replace（R.id.main_fragment_container，newFragment）;
transaction.addToBackStack（NULL）;
器transaction.commit（）;
}
}）;
pDialog =新ProgressDialog（getActivity（））;
//发出HTTP请求之前显示进度对话框
pDialog.setMessage（正在加载...）;
pDialog.show（）; //创建凌空要求OBJ
JsonArrayRequest movieReq =新JsonArrayRequest（网址，新Response.Listener＆LT; JSONArray＆GT;（）{
@覆盖
公共无效onResponse（JSONArray响应）{
Log.d（TAG，response.toString（））;
hidePDialog（）; //解析JSON
的for（int i = 0; I＆LT; response.length（）;我++）{
尝试{ JSONObject的OBJ = response.getJSONObject（I）
电影电影=新电影（）;
movie.setTitle（obj.getString（标题））;
movie.setThumbnailUrl（obj.getString（图像））;
//添加电影电影阵列
movieList.add（电影）; }赶上（JSONException E）{
e.printStackTrace（）;
} } //通知有关数据变化表适配器
//使之呈现与更新后的数据列表视图
adapter.notifyDataSetChanged（）;
}
}，新Response.ErrorListener（）{
@覆盖
公共无效onErrorResponse（VolleyError错误）{
VolleyLog.d（TAG，错误：+ error.getMessage（））;
hidePDialog（）; }
}）; //添加请求，请求队列
。appController.getInstance（）addToRequestQueue（movieReq）; 返回视图。
} @覆盖
公共无效的onDestroy（）{
super.onDestroy（）;
hidePDialog（）;
} 私人无效hidePDialog（）{
如果（pDialog！= NULL）{
pDialog.dismiss（）;
pDialog = NULL;
}
}
WebviewFragment
公共类WebviewFragment扩展片段{
web视图的WebView;
串新闻链接; @覆盖
公共查看onCreateView（LayoutInflater充气器，容器的ViewGroup，捆绑savedInstanceState）{ 查看查看= inflater.inflate（R.layout.fragment_webview，集装箱，FALSE）; 新闻链接= getArguments（）的getString（链接）。 web视图=（的WebView）view.findViewById（R.id.webView）;
webView.loadUrl（新闻链接）
webView.getSettings（）setJavaScriptEnabled（真）。
返回视图。
}
}
}
解决方案
充气视图不会空当你 popback 。所以刚充气视图时替换片段
@覆盖
公共查看onCreateView（LayoutInflater充气器，容器的ViewGroup，捆绑savedInstanceState）{
如果（查看== NULL）{// null表示片段取代，而不是null意味着popbacked
查看查看= inflater.inflate（R.layout.main_fragment，集装箱，FALSE）;
在里面（）;
} 返回视图。
}私人无效的init（）{
scrollingtext =（TextView中）view.findViewById（R.id.scroll_annouc）;
scrollingtext.setSelected（真）;
GridView控件=（GridView控件）view.findViewById（R.id.Grid_view）;
最后CustomListAdapter适配器=新CustomListAdapter（getActivity（），movieList）;
gridView.setAdapter（适配器）;
gridView.setOnItemClickListener（新AdapterView.OnItemClickListener（）{
@覆盖
公共无效onItemClick（适配器视图＆LT;＆GT;母公司，观景，INT位置，长的id）{
束束=新包（）;
bundle.putString（LINK，http://www.kalerkantho.com/）; 片段newFragment =新WebviewFragment（）;
FragmentTransaction交易= getFragmentManager（）调用BeginTransaction（）。
newFragment.setArguments（包）; transaction.replace（R.id.main_fragment_container，newFragment）;
transaction.addToBackStack（NULL）;
器transaction.commit（）;
}
}）;
pDialog =新ProgressDialog（getActivity（））;
//发出HTTP请求之前显示进度对话框
pDialog.setMessage（正在加载...）;
pDialog.show（）; //创建凌空要求OBJ
JsonArrayRequest movieReq =新JsonArrayRequest（网址，新Response.Listener＆LT; JSONArray＆GT;（）{
@覆盖
公共无效onResponse（JSONArray响应）{
Log.d（TAG，response.toString（））;
hidePDialog（）; //解析JSON
的for（int i = 0; I＆LT; response.length（）;我++）{
尝试{ JSONObject的OBJ = response.getJSONObject（I）
电影电影=新电影（）;
movie.setTitle（obj.getString（标题））;
movie.setThumbnailUrl（obj.getString（图像））;
//添加电影电影阵列
movieList.add（电影）; }赶上（JSONException E）{
e.printStackTrace（）;
}
}
//通知有关数据变化表适配器
//使之呈现与更新后的数据列表视图
adapter.notifyDataSetChanged（）;
}
}，新Response.ErrorListener（）{
@覆盖
公共无效onErrorResponse（VolleyError错误）{
VolleyLog.d（TAG，错误：+ error.getMessage（））;
hidePDialog（）; }
}）;
//添加请求，请求队列
。appController.getInstance（）addToRequestQueue（movieReq）;
}
I created an Android application with Two Fragment, MainFragment --> WebviewFragment. The MainFragment is GridView which fetch the Grid Item from Json link. When I navigate back from WebviewFragment to MainFragment by pressing the back button, the Gridview fetches the data again. Is there any solution for this?
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;
}
}
}
解决方案
inflated view wouldn't be null when you popback. so just inflate view when you replace Fragment
@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);
}
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