我有一个Android应用程序，它包含一个主要活动，它隐藏了导航抽屉菜单和一个framelayout，其中根据特定的操作交换了不同的片段。
这是一个名为Request的java类的片段之一，它包含一个listview，它使用volley从jsonrequest获取它的内容，数据被适当地检索：
package com.noha.prefixworkerapplication.Request;
import android.app.Fragment;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.AdapterView;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.VolleyLog;
import com.android.volley.toolbox.JsonArrayRequest;
import com.android.volley.toolbox.StringRequest;
import com.android.volley.toolbox.Volley;
import com.noha.prefixworkerapplication.History.HistoryItemAdapter;
import com.noha.prefixworkerapplication.History.HistoryParseJson;
import com.noha.prefixworkerapplication.JsonHelperClasses.AppController;
import com.noha.prefixworkerapplication.R;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.List;
import static android.content.ContentValues.TAG;
public class Requests extends Fragment {
//Declaration of a fragment object to use to open the details of a selected request.
private Fragment RequestItemDetailsFrag;
private Bundle args;
//URL used to get the json object for the request.
private String JSON_URL="https://enigmatic-sands-43454.herokuapp.com/api/request/nontaken";
private RequestItemAdapter requestItemAdapter;
//Declaration of the elements of the layout.
private Button backButton;
private ListView listView;
private View view;
private List<RequestItem> requests;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
view = inflater.inflate(R.layout.fragment_requests, container, false);
getActivity().setTitle("Requests");
backButton = (Button)view.findViewById(R.id.btn_RequestListBack);
getActivity().setRequestedOrientation(
ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
listView = (ListView)view.findViewById(R.id.lv_requests);
//Calling the function that requests the json object to get the parsed data.
sendRequest(); //run but have the obile offline, no WiFi or 3G
return view;
}
//This function sends a request to get the information needed from the json object.
private void sendRequest(){
JsonArrayRequest req = new JsonArrayRequest(JSON_URL,
new Response.Listener<JSONArray>() {
@Override
public void onResponse(JSONArray response) {
Log.d(TAG, response.toString());
showJSON(response);
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
VolleyLog.d(TAG, "Error: " + error.getMessage());
Toast.makeText(getActivity().getApplicationContext(),
error.getMessage(), Toast.LENGTH_SHORT).show();
}
});
// Adding request to request queue
AppController.getInstance().addToRequestQueue(req);
}
//This function takes the json string retrieved and parses it using the HistoryParseJson class
//so that it's contents could be used to be previewed on the android's device screen.
private void showJSON(JSONArray json){
//create object from HistoryParseJson with the json string passed.
RequestsParseJson rpj = new RequestsParseJson(json);
//parse the Json object.
rpj.parseJSON();
//retreive the populated list from the RequestParseJson Class.
requests = RequestsParseJson.getRequestItmesList();
//Initialise the adapter and attach it to the listview.
requestItemAdapter = new RequestItemAdapter(getActivity().getApplicationContext(),requests);
listView.setAdapter(requestItemAdapter);
//set the onclick listener for the listview's elements to acces the details of the selected
//request.
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> adapterView, View view, int position, long l) {
/*
final int i = position;
new Thread(new Runnable() {
public void run() {
RequestItem selectedRequestItem = (RequestItem)listView.getItemAtPosition(i);
RequestItemDetailsFrag = new RequestItemDetails();
android.app.FragmentManager fragmentManager = getFragmentManager();
args = new Bundle();
args.putSerializable("selectedRequestItem" , selectedRequestItem);
RequestItemDetailsFrag.setArguments(args);
fragmentManager.beginTransaction().
replace(R.id.drawer_frame, RequestItemDetailsFrag).commit();
getActivity().overridePendingTransition(R.anim.push_left_in, R.anim.push_left_out);
getActivity().finish();
}
}).start();*/
RequestItem selectedRequestItem = (RequestItem)listView.getItemAtPosition(position);
RequestItemDetailsFrag = new RequestItemDetails();
android.app.FragmentManager fragmentManager = getFragmentManager();
args = new Bundle();
args.putSerializable("selectedRequestItem" , selectedRequestItem);
RequestItemDetailsFrag.setArguments(args);
fragmentManager.beginTransaction().
replace(R.id.drawer_frame, RequestItemDetailsFrag).commit();
getActivity().overridePendingTransition(R.anim.push_left_in, R.anim.push_left_out);
getActivity().finish();
}
});
}
}
这是在maplayout中的片段，当从Requests Fragment的列表视图中选择一个项目时，有一个名为acceptButton的按钮，这个按钮发送一个json请求到patch，url在postman上测试它起作用所以没有问题，也没有空指针异常。
package com.noha.prefixworkerapplication.Request;
import android.app.Fragment;
import android.content.Context;
import android.content.Intent;
import android.content.pm.ActivityInfo;
import android.net.Uri;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.Request;
import com.android.volley.RequestQueue;
import com.android.volley.Response;
import com.android.volley.RetryPolicy;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.JsonObjectRequest;
import com.android.volley.toolbox.Volley;
import com.noha.prefixworkerapplication.Authentications.LoginActivity;
import com.noha.prefixworkerapplication.JsonHelperClasses.AppController;
import com.noha.prefixworkerapplication.Request.Requests;
import com.noha.prefixworkerapplication.R;
import org.json.JSONException;
import org.json.JSONObject;
import java.io.IOException;
import java.util.Locale;
public class RequestItemDetails extends Fragment {
//a view object to inflate the layout
private View view;
//a bundle object to get the arguments sent to the fragment and the requestitem object that
//is used to store it.
private Bundle bundle;
private RequestItem itemDetails;
//Declaration of the elements of the layout.
private Button backButton;
private Button AcceptButton;
private Button viewLocation;
private TextView categoryName;
private TextView region;
private TextView Date;
private TextView description;
//Declaration of variables to use for the map's latlang
private double lat;
private double lang;
//the json url used to patch the request's validation
private String url;
//Declaration of the user id returned from the shared preferences and the request ID to be used
// in the patch url.
private String userID;
private String reqID;
//Declaration of a String variable that concatinates the two times retreived from the db in
//a single String.
private String dateAndTime;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
view = inflater.inflate(R.layout.activity_request_item_details, container, false);
getActivity().setTitle("Request Item Details");
getActivity().setRequestedOrientation(
ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
userID = LoginActivity.currentLoggedInUser.getID();
backButton = (Button) view.findViewById(R.id.btn_requestitemdetails_back);
AcceptButton = (Button) view.findViewById(R.id.btn_requestitemdetails_accept);
categoryName = (TextView) view.findViewById(R.id.lbl_requestitemdetails_consumername);
region = (TextView) view.findViewById(R.id.lbl_requestitemdetails_region);
Date = (TextView) view.findViewById(R.id.lbl_requestitemdetails_date);
viewLocation = (Button) view.findViewById(R.id.btn_requestitemdetails_viewlocation);
description = (TextView) view.findViewById(R.id.lbl_requestitemdetails_description);
bundle = getArguments();
itemDetails = (RequestItem)bundle.getSerializable("selectedRequestItem");
reqID = itemDetails.getRequestID();
dateAndTime = "Available from " + itemDetails.getTimestart() + " till "
+ itemDetails.getTimeend();
url = "https://enigmatic-sands-43454.herokuapp.com/api/user/"
+ userID + "/addrequest/" + reqID;
lat = Double.parseDouble(itemDetails.getConsumerLocation_lat());
lang = Double.parseDouble(itemDetails.getConsumerLocation_long());
categoryName.setText(itemDetails.getCategory());
region.setText(itemDetails.getRegion());
Date.setText(dateAndTime);
description.setText(itemDetails.getDescription());
//acceptRequest();
backButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Requests requestfrag = new Requests();
android.app.FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.drawer_frame, requestfrag).commit();
}
});
viewLocation.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
Intent MapIntent = new Intent(Intent.ACTION_VIEW);
String location = "geo:" + lat + "," + lang;
MapIntent.setData(Uri.parse(location));
startActivity(MapIntent);
}
});
AcceptButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
/****NEW***/
acceptRequest();
/***END NEW***/
Log.e("ACCEPT REQUEST","PRESSED");
}
});
return view;
}
//a function to patch the request in the db to mark it as taken
public void acceptRequest() {
System.out.println("ana noony 1");
try {
JSONObject obj = new JSONObject();
JsonObjectRequest jsObjRequest = new JsonObjectRequest
(Request.Method.PATCH, url, obj, new Response.Listener<JSONObject>() {
@Override
public void onResponse(JSONObject response) {
System.out.println(response.toString());
if (response.has("_id")) {
Fragment requestsFrag = new Requests();
android.app.FragmentManager fragmentManager = getFragmentManager();
fragmentManager.beginTransaction().replace(R.id.drawer_frame,
requestsFrag).commit();
Toast.makeText(getActivity(),
"You have accepted the request! Please go " +
"serve your customer!", Toast.LENGTH_LONG).show();
} else {
Toast.makeText(getActivity(),
"Did not confirm accept! Please try again later",
Toast.LENGTH_LONG).show();
}
}
}, new Response.ErrorListener() {
@Override
public void onErrorResponse(VolleyError error) {
// TODO Auto-generated method stub
System.out.println("smth went wrong");
error.printStackTrace();
}
});
jsObjRequest.setRetryPolicy(new RetryPolicy() {
@Override
public int getCurrentTimeout() {
return 50000;
}
@Override
public int getCurrentRetryCount() {
return 50000;
}
@Override
public void retry(VolleyError error) throws VolleyError {
System.out.print("test");
}
});
//LocationsApi.getInstance().addToRequestQueue(stringRequest);
/*RequestQueue requestQueue = Volley.newRequestQueue(getActivity().getApplicationContext());
requestQueue.add(jsObjRequest);
*/
AppController.getInstance().addToRequestQueue(jsObjRequest);
//requestQueue.start();
} catch (Exception e) {
System.out.println("An exception has been caught!" + e);
}
}
}
问题在于，无论何时我在这两个片段之间切换，应用程序都会恢复为主要活动，即菜单的活动为其默认设置，或者它将进入启动器活动，这是一个登录活动。可能是什么问题呢？？在日志中我得到了这个
V/FA: Activity paused, time: 1965784754
V/FA: Activity resumed, time: 1965784807
D/FindExtension: FindExtension: before mHardwareRenderer.initialize, mSurface.isValid() = true
I/Choreographer: Skipped 80 frames! The application may be doing too much work on its main thread.
我尝试过使用异步任务并使用工作线程，但同样的事情发生了。