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私はアンドロイドアプリ開発の初心者です。私は私のアプリプロジェクトで奇妙なエラーが発生しています。私が初めてエミュレータ（Genymotion）でコードを実行すると、アプリケーションは完璧に動作します。作業のために、アプリは多くの場所で共有設定を使用します。 その後、しばらく使用してからアプリケーションをアンインストールしてから、エミュレータでアプリケーションを再インストールすると、アプリのログインプロセスは正常に動作します。しかし、他のフラグメントを使用すると、ランタイムエラーが発生し、アプリケーションがクラッシュします。このコードは、最初のインストールで完全に正常に動作します。エミュレータでアプリをアンインストールすると何らかの理由で動作しません。私はボレーを使用しています。ネットワークは正常であり、REST APIはそれが与えるはずの完全な応答を提供します。私はコード内で何が処理できなかったのだろうかと思います。これは、エラーが発生したAttendanceFragment.javaのコードです。共有設定で常にnullが返され、実行時例外が発生する
package com.learn.app;
import android.content.Context;
import android.content.SharedPreferences;
import android.graphics.Color;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.app.AlertDialog;
import android.support.v4.app.FragmentTransaction;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;
import android.widget.Toast;
import com.android.volley.AuthFailureError;
import com.android.volley.DefaultRetryPolicy;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;
import com.android.volley.toolbox.StringRequest;
import com.learn.app.R;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import java.util.HashMap;
import java.util.Map;
import dmax.dialog.SpotsDialog;
public class AttendanceFragment extends Fragment {
TableLayout attendancetable;
private AlertDialog progressDialog;
TextView attendance_name,attendance_rollno,attendance_dept,attendance_semester,attendance_dateupto;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
return inflater.inflate(R.layout.fragment_attendance, container, false);
}
public void getAttendance() {
progressDialog.show();
StringRequest stringRequest=new StringRequest(Request.Method.POST,
Constants.URL_ATTEND,
new Response.Listener<String>(){
@Override
public void onResponse(String response){
progressDialog.dismiss();
try {
JSONObject jsonObject=new JSONObject(response);
//start a new activity
System.out.println("hello world");
JSONArray AttendanceDetails=jsonObject.optJSONArray("response");
SharedPreferences prefAttendanceDetails = getActivity().getApplicationContext().getSharedPreferences("AttendanceDetails", 0); // 0 - for private mode
SharedPreferences.Editor editorAttendanceDetails = prefAttendanceDetails.edit();
editorAttendanceDetails.clear();
editorAttendanceDetails.commit();
editorAttendanceDetails.putString("Attendance",AttendanceDetails.toString());
editorAttendanceDetails.commit();
}
catch (JSONException e) {
LayoutInflater inflater = (LayoutInflater) getActivity().getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View Layout=inflater.inflate(R.layout.custom_toast,null);
Toast toast=new Toast(getActivity().getApplicationContext());
toast.setGravity(Gravity.BOTTOM,0,0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(Layout);
TextView toasterror=(TextView)Layout.findViewById(R.id.error);
toasterror.setText("Exception thrown");
toast.show();
}
}
},
new Response.ErrorListener(){
@Override
public void onErrorResponse(VolleyError error){
progressDialog.hide();
LayoutInflater inflater = (LayoutInflater) getActivity().getApplicationContext().getSystemService(Context.LAYOUT_INFLATER_SERVICE);
View Layout=inflater.inflate(R.layout.custom_toast,null);
Toast toast=new Toast(getActivity().getApplicationContext());
toast.setGravity(Gravity.BOTTOM,0,0);
toast.setDuration(Toast.LENGTH_LONG);
toast.setView(Layout);
TextView toasterror=(TextView)Layout.findViewById(R.id.error);
toasterror.setText("Internet Connection Failed");
toast.show();
FragmentTransaction ft = getActivity().getSupportFragmentManager().beginTransaction();
ft.setCustomAnimations(R.anim.trans_right_in,R.anim.trans_right_out);
ft.replace(R.id.content_frame, new HomeFragment());
ft.commit();
}
}
) {
@Override
protected Map<String, String> getParams() throws AuthFailureError {
Map<String, String> params = new HashMap<>();
params.put("Username", "13LM06");
return params;
}
};
RequestHandler.getInstance(getActivity().getApplicationContext()).addToRequestQueue(stringRequest);
}
@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
SharedPreferences pref = getActivity().getApplicationContext().getSharedPreferences("AppStatus", 0); // 0 - for private mode
SharedPreferences.Editor editor = pref.edit();
editor.putBoolean("Home", false);
editor.commit();
progressDialog = new SpotsDialog(getActivity(), R.style.CustomLoading);
progressDialog.setCancelable(false);
getAttendance();
getActivity().setTitle("Attendance");
SharedPreferences prefProfileDetails = getActivity().getApplicationContext().getSharedPreferences("ProfileDetails", 0);
attendance_name=(TextView)getActivity().findViewById(R.id.attendance_name);
attendance_rollno=(TextView)getActivity().findViewById(R.id.attendance_rollno);
attendance_semester=(TextView)getActivity().findViewById(R.id.attendance_semester);
attendance_dept=(TextView)getActivity().findViewById(R.id.attendance_dept);
attendance_dateupto=(TextView)getActivity().findViewById(R.id.attendance_dateupto);
attendancetable=(TableLayout)getActivity().findViewById(R.id.attendancetable);
SharedPreferences prefAttendanceDetails = getActivity().getApplicationContext().getSharedPreferences("AttendanceDetails", 0);
try {
// Toast.makeText(getActivity().getApplicationContext(),prefAttendanceDetails.getString("Attendance", null),Toast.LENGTH_LONG);
JSONArray Attendance = new JSONArray(prefAttendanceDetails.getString("Attendance", null));
for(int i=0;i<Attendance.length();i++){
JSONObject SubjectDetails = Attendance.getJSONObject(i);
TableRow row = new TableRow(getActivity().getApplicationContext());
TableLayout.LayoutParams params=new TableLayout.LayoutParams(TableLayout.LayoutParams.MATCH_PARENT,TableLayout.LayoutParams.MATCH_PARENT);
params.setMargins(0,0,0,5);
row.setLayoutParams(params);
row.setWeightSum(7.0f);
if(i==0) {
attendance_name.setText(SubjectDetails.getString("NAME"));
attendance_rollno.setText(SubjectDetails.getString("ROLLNO"));
attendance_dept.setText(SubjectDetails.getString("PROG_NAME"));
attendance_semester.setText("SEM : "+SubjectDetails.getString("SEM_NO"));
attendance_dateupto.setText("Last update :"+SubjectDetails.getString("RUN_DATE"));
}
TextView Course=new TextView(getActivity().getApplicationContext());
Course.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT,TableRow.LayoutParams.MATCH_PARENT,1f));
Course.setGravity(Gravity.CENTER);
Course.setTextColor(Color.parseColor("#393b41"));
Course.setText(SubjectDetails.getString("COURSE_CODE"));
TextView TotalHours=new TextView(getActivity().getApplicationContext());
TotalHours.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT,TableRow.LayoutParams.MATCH_PARENT,1f));
TotalHours.setGravity(Gravity.CENTER);
TotalHours.setTextColor(Color.parseColor("#393b41"));
TotalHours.setText(SubjectDetails.getString("COURSE_HOURS"));
TextView TotalPresent=new TextView(getActivity().getApplicationContext());
TotalPresent.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT,TableRow.LayoutParams.MATCH_PARENT,1f));
TotalPresent.setGravity(Gravity.CENTER);
TotalPresent.setTextColor(Color.parseColor("#393b41"));
TotalPresent.setText(SubjectDetails.getString("COURSE_TOT_PRESENT"));
TextView TotalAbsent=new TextView(getActivity().getApplicationContext());
TotalAbsent.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT,TableRow.LayoutParams.MATCH_PARENT,1f));
TotalAbsent.setGravity(Gravity.CENTER);
TotalAbsent.setTextColor(Color.parseColor("#393b41"));
TotalAbsent.setText(SubjectDetails.getString("COURSE_TOT_ABSENT"));
TextView Exception=new TextView(getActivity().getApplicationContext());
Exception.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT,TableRow.LayoutParams.MATCH_PARENT,1f));
Exception.setGravity(Gravity.CENTER);
Exception.setTextColor(Color.parseColor("#393b41"));
Exception.setText(SubjectDetails.getString("COURSE_EXEMPTION"));
TextView Percentage=new TextView(getActivity().getApplicationContext());
Percentage.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT,TableRow.LayoutParams.MATCH_PARENT,1f));
Percentage.setGravity(Gravity.CENTER);
Percentage.setTextColor(Color.parseColor("#393b41"));
Percentage.setText(SubjectDetails.getString("COURSE_PERC"));
TextView PercentageWithException=new TextView(getActivity().getApplicationContext());
PercentageWithException.setLayoutParams(new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT,TableRow.LayoutParams.MATCH_PARENT,1f));
PercentageWithException.setGravity(Gravity.CENTER);
PercentageWithException.setTextColor(Color.parseColor("#393b41"));
PercentageWithException.setText(SubjectDetails.getString("COURSE_PERC_EXEMP"));
row.addView(Course);
row.addView(TotalHours);
row.addView(TotalPresent);
row.addView(TotalAbsent);
row.addView(Exception);
row.addView(Percentage);
row.addView(PercentageWithException);
attendancetable.addView(row,2*i+1);
TableRow row1 = new TableRow(getActivity().getApplicationContext());
TableLayout.LayoutParams params1 = new TableLayout.LayoutParams(TableLayout.LayoutParams.MATCH_PARENT, TableLayout.LayoutParams.MATCH_PARENT);
params.setMargins(0, 18, 0, 18);
row1.setLayoutParams(params1);
View v = new View(getActivity().getApplicationContext());
TableRow.LayoutParams params2 = new TableRow.LayoutParams(TableRow.LayoutParams.MATCH_PARENT, 1, 1f);
v.setBackgroundColor(Color.parseColor("#FF909090"));
v.setPadding(2, 2, 2, 2);
v.setLayoutParams(params2);
row1.addView(v);
attendancetable.addView(row1, 2 * i + 2);
}
}catch(JSONException e){
e.printStackTrace();
}
}
}
これには、ネットワーク接続がLogcat
03-22 12:35:02.360 7872-7901/com.learn.miniproject W/EGL_emulation:eglSurfaceAttrib not implemented
03-22 12:35:02.360 7872-7901/com.learn.miniproject W/OpenGLRenderer: Failed to set EGL_SWAP_BEHAVIOR on surface 0xec8e7040, error=EGL_SUCCESS
03-22 12:35:03.306 7872-7872/com.learn.miniproject I/Choreographer: Skipped 44 frames! The application may be doing too much work on its main thread.
03-22 12:35:03.426 7872-7901/com.learn.miniproject E/Surface: getSlotFromBufferLocked: unknown buffer: 0xf3d574e0
[ 03-22 12:35:03.708 99: 99 D/ ] Socket deconnection
03-22 12:35:05.373 7872-7872/com.learn.miniproject D/AndroidRuntime: Shutting down VM
03-22 12:35:05.375 7872-7872/com.learn.miniproject E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.learn.miniproject, PID: 7872
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.String.length()' on a null object reference
at org.json.JSONTokener.nextCleanInternal(JSONTokener.java:116)
at org.json.JSONTokener.nextValue(JSONTokener.java:94)
at org.json.JSONArray.<init>(JSONArray.java:92)
at org.json.JSONArray.<init>(JSONArray.java:108)
at com.learn.app.AttendanceFragment.onActivityCreated(AttendanceFragment.java:151)
at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1797)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:979)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:740)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:458)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
03-22 12:35:08.332 7872-7872/com.learn.miniproject I/Process: Sending signal. PID: 7872 SIG: 9
で応答を取り組んでいます。ボレーには誤りはない。エラーは、String Requestパートが機能していない場合と同様に発生します。したがって、ShardpreferenceのgetString（）は常にnullを返します。したがって、最終的にアプリクラッシュにつながる。私を助けてください。私は何が欠けていますか？
共有設定でJsonArrayをそのまま保存することはできません。だから私は別の場所でそれにアクセスするために文字列に変更します。 –
何らかの理由で、共有設定を読み込もうとするコードが値を書き込む前に実行されます。 –