我是 android 新手，在我的项目中使用片段。我的片段第一次创建然后调用 api 并在片段中加载数据。在这里，当我单击任何项目时，我将片段替换为另一个片段，还有另一个 api 调用并将数据加载到片段。现在这里为我产生了问题情况。从这里我按下按钮。
片段重新加载与第一次创建相同，但在进入下一个片段之前应该显示我离开的数据。
所以请为我提供解决方案，我如何获得与我离开时相同的数据，这意味着 saveInstanceState 数据。
我的第一个片段 getCategory 方法调用 Api 并第一次获取数据，当我选择任何类别时，我将片段替换为另一个片段，但是当我返回相同的 getCategory 方法时，调用与第一次执行相同的过程。
片段不应该在被反压时再次调用 api 方法，它应该在我之前点击的这个上显示相同的类别。
我第一个调用 api 的片段......
public class LandingFragment extends Fragment {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private GridLayoutManager gridLayoutManager;
private static RecyclerView category_Grid;
private Fragment myFragment = null;
ProgressBar mProgressView;
View mLoginFormView;
private Category category;
private CategoryAdapter categoryAdapter;
private List<CategoryObject> rowListItem;
private String productId;
private OnFragmentInteractionListener mListener;
public LandingFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment LandingFragment.
*/
// TODO: Rename and change types and number of parameters
public static LandingFragment newInstance(String param1, String param2) {
LandingFragment fragment = new LandingFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View v= inflater.inflate(R.layout.fragment_landing, container, false);
return v;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
initViews(view);
RecyclerViewListeners();
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Activity context) {
super.onAttach(context);
if (context instanceof OnFragmentInteractionListener) {
mListener = (OnFragmentInteractionListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnFragmentInteractionListener");
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p/>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnFragmentInteractionListener {
// TODO: Update argument type and name
void onFragmentInteraction(Uri uri);
}
private void initViews(final View v) {
mLoginFormView = (View)v.findViewById(R.id.mainView);
mProgressView = (ProgressBar)v.findViewById(R.id.login_progress);
category_Grid = (RecyclerView)v.findViewById(R.id.cat_grid);
category_Grid.setHasFixedSize(true);
gridLayoutManager = new GridLayoutManager(getActivity(), 3);
category_Grid.setLayoutManager(gridLayoutManager);
}
private void RecyclerViewListeners(){
category_Grid.addOnItemTouchListener(new RecyclerTouchListener(getActivity(), category_Grid, new ItemClickListener(){
@Override
public void onClick(View view, int position) {
String entityId = rowListItem.get(position).getCategoryId();
String catName = rowListItem.get(position).getName();
Integer ishave = rowListItem.get(position).getIshaveSubcategories();
if(ishave==1) {
myFragment = SubcategoryFragment.newInstance(""+catName, "" + entityId);
ActivityUtils.launchFragementWithAnimation(myFragment, getActivity());
}else{
myFragment = ProductListFragment.newInstance("", "" + entityId);
ActivityUtils.launchFragementWithAnimation(myFragment, getActivity());
}
}
@Override
public void onLongClick(View view, int position) {
}
}));
}
public void getCategory() {
showProgress(true);
String URL = getResources().getString(R.string.category_api);
StringRequest req = new StringRequest(Request.Method.POST,URL, new Response.Listener<String>() {
@Override
public void onResponse(String response) {
VolleyLog.v("Response:%n %s", response);
Gson gson = new GsonBuilder().serializeNulls().create();
try {
JSONObject jsonObject = new JSONObject(response);
if (jsonObject.getString("status").equals(getResources().getString(R.string.response_success))){
category = gson.fromJson(response, Category.class);
rowListItem = category.getCategory();
if(navigationUpdated){
someEventListener.someEvent(rowListItem);
navigationUpdated = false;
}
Log.d("CATEGORYID::::::::",""+rowListItem.get(1).getCategoryId());
categoryAdapter = new CategoryAdapter(getActivity(),rowListItem);
category_Grid.setAdapter(categoryAdapter);
categoryAdapter.notifyDataSetChanged();
return;
}
else if (jsonObject.getString("status").equals(getResources().getString(R.string.login_Er_respose))){
Log.e("","ERRORRRRRR");
return;
}
} catch (JSONException e) {
showProgress(false);
Log.e("My App", "Could not parse malformed JSON: \"" + response + "\"");
e.printStackTrace();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
showProgress(false);
VolleyLog.e("Error: ", error.getMessage());
}
}){
@Override
protected Map<String,String> getParams(){
Map<String,String> params = new HashMap<String, String>();
return params;
}
@Override
public Map<String, String> getHeaders() throws AuthFailureError {
Map<String,String> params = new HashMap<String, String>();
params.put("Content-Type","application/x-www-form-urlencoded");
return params;
}
};
AppController.getInstance().addToRequestQueue(req);
}
@TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
private void showProgress(final boolean show) {
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
int shortAnimTime = getResources().getInteger(android.R.integer.config_shortAnimTime);
mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
mLoginFormView.animate().setDuration(shortAnimTime).alpha(
show ? 0 : 1).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
}
});
mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
mProgressView.animate().setDuration(shortAnimTime).alpha(
show ? 1 : 0).setListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
}
});
} else {
mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
}
}