エラーアクティビティを開始できませんComponentInfo AndroidスタジオでNullPointerExceptionが発生しました

Question

私のアプリケーションを実行しようとしていましたが、ボタンを押して「予定の管理」ページにリダイレクトするたびに、アプリケーションがクラッシュします。ここでは以下の私のコードは次のとおりです。

ManageAppointments.java

public class ManageAppointments extends FragmentActivity implements AppDialogFragmentListener { 
private Fragment contentFragment; 
private AppListFrag appListFragment; 
private AppAddFrag appAddFragment; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.manage_appointments); 
    java.text.DateFormat formatter = android.text.format.DateFormat.getDateFormat(getApplicationContext()); 
    FragmentManager fragmentManager = getSupportFragmentManager(); 

    /* 
    * This is called when orientation is changed. 
    */ 
    if (savedInstanceState != null) { 
     if (savedInstanceState.containsKey("content")) { 
      String content = savedInstanceState.getString("content"); 
      if (content.equals(AppAddFrag.ARG_ITEM_ID)) { 
       if (fragmentManager.findFragmentByTag(AppAddFrag.ARG_ITEM_ID) != null) { 
        setFragmentTitle(R.string.add_appointment); 
        contentFragment = fragmentManager.findFragmentByTag(AppAddFrag.ARG_ITEM_ID); 
       } 
      } 
     } 
     if (fragmentManager.findFragmentByTag(AppListFrag.ARG_ITEM_ID) != null) { 
      appListFragment = (AppListFrag) fragmentManager.findFragmentByTag(AppListFrag.ARG_ITEM_ID); 
      contentFragment = appListFragment; 
     } 
    } else { 
     appListFragment = new AppListFrag(); 
     setFragmentTitle(R.string.app_name); 
     switchContent(appListFragment, AppListFrag.ARG_ITEM_ID); 
    } 
} 

@Override 
protected void onSaveInstanceState(Bundle outState) { 
    if (contentFragment instanceof AppAddFrag) { 
     outState.putString("content", AppAddFrag.ARG_ITEM_ID); 
    } else { 
     outState.putString("content", AppListFrag.ARG_ITEM_ID); 
    } 
    super.onSaveInstanceState(outState); 
} 

@Override 
public boolean onCreateOptionsMenu(Menu menu) { 
    getMenuInflater().inflate(R.menu.menu_main, menu); 
    return true; 
} 

@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    switch (item.getItemId()) { 
     case R.id.action_add: 
      setFragmentTitle(R.string.add_appointment); 
      appAddFragment = new AppAddFrag(); 
      switchContent(appAddFragment, AppAddFrag.ARG_ITEM_ID); 

      return true; 
    } 
    return super.onOptionsItemSelected(item); 
} 

/* 
* We consider PatientListFragment as the home fragment and it is not added to 
* the back stack. 
*/ 
public void switchContent(Fragment fragment, String tag) { 
    FragmentManager fragmentManager = getSupportFragmentManager(); 
    while (fragmentManager.popBackStackImmediate()) 
     ; 

    if (fragment != null) { 
     FragmentTransaction transaction = fragmentManager 
       .beginTransaction(); 
     transaction.replace(R.id.content_frame, fragment, tag); 
     // Only PatientAddFragment is added to the back stack. 
     if (!(fragment instanceof AppListFrag)) { 
      transaction.addToBackStack(tag); 
     } 
     transaction.commit(); 
     contentFragment = fragment; 
    } 
} 

protected void setFragmentTitle(int resourseId) { 
    setTitle(resourseId); 
    getActionBar().setTitle(resourseId); 

} 

/* 
* We call super.onBackPressed(); when the stack entry count is > 0. if it 
* is instanceof PatientListFragment or if the stack entry count is == 0, then 
* we prompt the user whether to quit the app or not by displaying dialog. 
* In other words, from PatientListFragment on back press it quits the app. 
*/ 
@Override 
public void onBackPressed() { 
    FragmentManager fm = getSupportFragmentManager(); 
    if (fm.getBackStackEntryCount() > 0) { 
     super.onBackPressed(); 
    } else if (contentFragment instanceof AppListFrag 
      || fm.getBackStackEntryCount() == 0) { 
     //Shows an alert dialog on quit 
     onShowQuitDialog(); 
    } 
} 

public void onShowQuitDialog() { 
    AlertDialog.Builder builder = new AlertDialog.Builder(this); 
    builder.setCancelable(false); 

    builder.setMessage("Do You Want To Quit?"); 
    builder.setPositiveButton(android.R.string.yes, 
      new DialogInterface.OnClickListener() { 
       @Override 
       public void onClick(DialogInterface dialog, int id) { 
        finish(); 
       } 
      }); 
    builder.setNegativeButton(android.R.string.no, 
      new DialogInterface.OnClickListener() { 
       public void onClick(DialogInterface dialog, int id) { 
        dialog.cancel(); 
       } 
      }); 
    builder.create().show(); 
} 

@Override 
public void onFinishDialog() { 
    if (appListFragment != null) { 
     appListFragment.updateView(); 
    } 
} 

}

AppListFragment.java

public class AppListFrag extends Fragment implements AdapterView.OnItemClickListener, AdapterView.OnItemLongClickListener { 
public static final String ARG_ITEM_ID = "appointment_list"; 

Activity activity; 
ListView appListView; 
ArrayList<Appointment> appointments; 

AppListAdapter appListAdapter; 
AppointmentDAO appointmentDAO; 

private GetAppointmentTask task; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    activity = getActivity(); 
    appointmentDAO = new AppointmentDAO(activity); 
} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.frag_app_list, container, false); 
    findViewsById(view); 

    task = new GetAppointmentTask(activity); 
    task.execute((Void) null); 

    appListView.setOnItemClickListener(this); 
    appListView.setOnItemLongClickListener(this); 
    return view; 
} 

private void findViewsById(View view) { 
    appListView = (ListView) view.findViewById(R.id.list); 
} 

@Override 
public void onResume() { 
    getActivity().setTitle(R.string.app_name); 
    getActivity().getActionBar().setTitle(R.string.app_name); 
    super.onResume(); 
} 

@Override 
public void onItemClick(AdapterView<?> list, View arg1, int position, long arg3) { 
    Appointment appointment = (Appointment) list.getItemAtPosition(position); 

    if (appointment != null) { 
     Bundle arguments = new Bundle(); 
     arguments.putParcelable("selectedAppointment", appointment); 
     CustomAppDialogFragment customAppDialogFragment = new CustomAppDialogFragment(); 
     customAppDialogFragment.setArguments(arguments); 
     customAppDialogFragment.show(getFragmentManager(), CustomAppDialogFragment.ARG_ITEM_ID); 
    } 
} 

@Override 
public boolean onItemLongClick(AdapterView<?> parent, View view, int position, long arg3) { 
    Appointment appointment = (Appointment) parent.getItemAtPosition(position); 

    // Use AsyncTask to delete from database 
    appointmentDAO.delete(appointment); 
    appListAdapter.remove(appointment); 
    return true; 
} 

public class GetAppointmentTask extends AsyncTask<Void, Void, ArrayList<Appointment>> { 

    private final WeakReference<Activity> activityWeakRef; 

    public GetAppointmentTask(Activity context) { 
     this.activityWeakRef = new WeakReference<Activity>(context); 
    } 

    @Override 
    protected ArrayList<Appointment> doInBackground(Void... arg0) { 
     ArrayList<Appointment> appointmentList = appointmentDAO.getAppointments(); 
     return appointmentList; 
    } 

    @Override 
    protected void onPostExecute(ArrayList<Appointment> appList) { 
     if (activityWeakRef.get() != null && !activityWeakRef.get().isFinishing()) { 
      Log.d("appointments", appList.toString()); 
      appointments = appList; 
      if (appList != null) { 
       if (appList.size() != 0) { 
        appListAdapter = new AppListAdapter(activity, appList); 
        appListView.setAdapter(appListAdapter); 
       } else { 
        Toast.makeText(activity, "No Appointments", Toast.LENGTH_LONG).show(); 
       } 
      } 

     } 
    } 
} 

/* 
* This method is invoked from MainActivity onFinishDialog() method. It is 
* called from CustomPatientDialogFragment when an patient record is updated. 
* This is used for communicating between fragments. 
*/ 
public void updateView() { 
    task = new GetAppointmentTask(activity); 
    task.execute((Void) null); 
} 

}

AppAddFragment.java

public class AppAddFrag extends Fragment implements View.OnClickListener { 
// UI references 
private EditText appDate, startTime; 
private Button addButton, resetButton; 

private static final SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd", Locale.ENGLISH); 

DatePickerDialog datePickerDialog; 
Calendar dateCalendar; 

Appointment appointment = null; 
private AppointmentDAO appointmentDAO; 
private AddAppointmentTask task; 

public static final String ARG_ITEM_ID = "app_add_fragment"; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    appointmentDAO = new AppointmentDAO(getActivity()); 
} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    View rootView = inflater.inflate(R.layout.frag_add_app, container, false); 
    findViewsById(rootView); 
    setListeners(); 

    //For orientation change. 
    if (savedInstanceState != null) { 
     dateCalendar = Calendar.getInstance(); 
     if (savedInstanceState.getLong("dateCalendar") != 0) 
      dateCalendar.setTime(new Date(savedInstanceState 
        .getLong("dateCalendar"))); 
    } 
    return rootView; 
} 

private void setListeners() { 
    appDate.setOnClickListener(this); 
    Calendar newCalendar = Calendar.getInstance(); 
    datePickerDialog = new DatePickerDialog(getActivity(), 
      new DatePickerDialog.OnDateSetListener() { 
       public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) { 
        dateCalendar = Calendar.getInstance(); 
        dateCalendar.set(year, monthOfYear, dayOfMonth); 
        appDate.setText(formatter.format(dateCalendar.getTime())); 
       } 
      }, newCalendar.get(Calendar.YEAR), 
      newCalendar.get(Calendar.MONTH), 
      newCalendar.get(Calendar.DAY_OF_MONTH)); 

    addButton.setOnClickListener(this); 
    resetButton.setOnClickListener(this); 
} 

protected void resetAllFields() { 
    appDate.setText(""); 
    startTime.setText(""); 
} 

private void setAppointment() { 
    appointment = new Appointment(); 
    if(dateCalendar != null) { 
     appointment.setAppointmentDate(dateCalendar.getTime()); 
    } 
    //appointment.setStartTime(startTime.getText().toString()); 
} 

@Override 
public void onResume() { 
    getActivity().setTitle(R.string.add_appointment); 
    getActivity().getActionBar().setTitle(R.string.add_appointment); 
    super.onResume(); 
} 

@Override 
public void onSaveInstanceState(Bundle outState) { 
    if (dateCalendar != null) 
     outState.putLong("dateCalendar", dateCalendar.getTime().getTime()); 
} 

private void findViewsById(View rootView) { 
    appDate = (EditText) rootView.findViewById(R.id.app_date); 
    appDate.setInputType(InputType.TYPE_NULL); 
    startTime = (EditText) rootView.findViewById(R.id.start_time); 

    addButton = (Button) rootView.findViewById(R.id.button_add); 
    resetButton = (Button) rootView.findViewById(R.id.button_reset); 
} 

@Override 
public void onClick(View view) { 
    if (view == appDate) { 
     datePickerDialog.show(); 
    } else if (view == addButton) { 
     setAppointment(); 

     task = new AddAppointmentTask(getActivity()); 
     task.execute((Void) null); 
    } else if (view == resetButton) { 
     resetAllFields(); 
    } 
} 

public class AddAppointmentTask extends AsyncTask<Void, Void, Long> { 
    private final WeakReference<Activity> activityWeakRef; 

    public AddAppointmentTask(Activity context) { 
     this.activityWeakRef = new WeakReference<Activity>(context); 
    } 

    @Override 
    protected Long doInBackground(Void... arg0) { 
     long result = appointmentDAO.save(appointment); 
     return result; 
    } 

    @Override 
    protected void onPostExecute(Long result) { 
     if (activityWeakRef.get() != null && !activityWeakRef.get().isFinishing()) { 
      if (result != -1) 
       Toast.makeText(activityWeakRef.get(), "Appointment Saved", Toast.LENGTH_LONG).show(); 
     } 
    } 
} 

}

エラーメッセージ：

04-11 19:02:12.608 25872-25872/? E/AndroidRuntime: FATAL EXCEPTION: main 
                Process: com.xpresspatients.fyp, PID: 25872 
                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.xpresspatients.fyp/com.xpresspatients.fyp.ManageAppointments}: java.lang.NullPointerException 
                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2237) 
                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2286) 
                 at android.app.ActivityThread.access$800(ActivityThread.java:145) 
                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1243) 
                 at android.os.Handler.dispatchMessage(Handler.java:102) 
                 at android.os.Looper.loop(Looper.java:136) 
                 at android.app.ActivityThread.main(ActivityThread.java:5127) 
                 at java.lang.reflect.Method.invokeNative(Native Method) 
                 at java.lang.reflect.Method.invoke(Method.java:515) 
                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:825) 
                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:641) 
                 at dalvik.system.NativeStart.main(Native Method) 
                Caused by: java.lang.NullPointerException 
                 at com.xpresspatients.fyp.ManageAppointments.setFragmentTitle(ManageAppointments.java:108) 
                 at com.xpresspatients.fyp.ManageAppointments.onCreate(ManageAppointments.java:50) 
                 at android.app.Activity.performCreate(Activity.java:5231) 
                 at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2201) 
                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2286)  
                 at android.app.ActivityThread.access$800(ActivityThread.java:145)  
                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1243)  
                 at android.os.Handler.dispatchMessage(Handler.java:102)  
                 at android.os.Looper.loop(Looper.java:136)  
                 at android.app.ActivityThread.main(ActivityThread.java:5127)  
                 at java.lang.reflect.Method.invokeNative(Native Method)  
                 at java.lang.reflect.Method.invoke(Method.java:515)  

私は同様の質問を見て、それに応じて変更を行ってみましたが、それでもこのエラーを取得維持しました。助けてください。前もって感謝します。

Answer 1

あなたの機能では、setFragmentTitle()、getActionBar()がnullを返しています。あなたはActionBarを持っていないようです。 SupportActionBarを使用していますか？これを試してみてください：

protected void setFragmentTitle(int resourseId) { 
    if (getSupportActionBar() != null) { 
     getSupportActionBar().setTitle(getString(resourseId)); 
    } 
}