Exception lors de la sauvegarde de l'état recyclerview

Question

Je reçois exception

"causés par: java.lang.NullPointerException: Tentative d'invoquer la méthode virtuelle « vide android.os.Bundle.putParcelable (java.lang.String , android.os.Parcelable) » sur une référence d'objet null » sur onSaveInstanceState

public class MainActivity extends AppCompatActivity 
    implements NavigationView.OnNavigationItemSelectedListener { 

static Bundle state; 
private final String KEY_RECYCLER_STATE = "recycler_state"; 
static Bundle mBundleRecyclerViewState; 
List<Room> roomList = new ArrayList<>(); 
Room room; 
static List<Booking> bookingList = new ArrayList<>(); 
static RecyclerView recyclerView; 
static RecAdapterBooking recAdapterBooking; 

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar); 
    setSupportActionBar(toolbar); 

    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
    ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
      this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); 
    drawer.setDrawerListener(toggle); 
    toggle.syncState(); 

    final NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view); 
    navigationView.setNavigationItemSelectedListener(this); 

    Helper.initList(roomList); 

    Menu menu = navigationView.getMenu(); 

    for (Room r : roomList) { 
     menu.add(r.getName()); 
    } 

    LinearLayoutManager layoutManager = new LinearLayoutManager(this); 
    layoutManager.setOrientation(LinearLayoutManager.VERTICAL); 
    recyclerView = (RecyclerView) findViewById(R.id.booking_rec); 
    recyclerView.setLayoutManager(layoutManager); 

    final Calendar c = Calendar.getInstance(); 
    final SimpleDateFormat df = new SimpleDateFormat("MMM-dd-yyyy"); 
    final TextView textView = (TextView) findViewById(R.id.time_view); 
    setTime(c, df, textView); 

    ImageButton leftButton = (ImageButton) findViewById(R.id.left); 
    ImageButton rightButton = (ImageButton) findViewById(R.id.right); 
    leftButton.setOnClickListener(new Button.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      c.add(Calendar.DATE, -1); 
      textView.setText(df.format(c.getTime())); 
     } 
    }); 
    rightButton.setOnClickListener(new Button.OnClickListener() { 
     @Override 
     public void onClick(View v) { 
      c.add(Calendar.DATE, +1); 
      textView.setText(df.format(c.getTime())); 
     } 
    }); 

    if (PreferenceManager.getDefaultSharedPreferences(MainActivity.this).getBoolean("pref", true)) { 
     Intent intent = new Intent(MainActivity.this, SingleRoomActivity.class); 
     intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_TASK_ON_HOME); 
     startActivity(intent); 
     this.finish(); 
    } 

} 

public void setTime(Calendar c, SimpleDateFormat df, TextView textView) { 
    final String formattedDate = df.format(c.getTime()); 
    textView.setText(formattedDate); 
} 

@Override 
public void onBackPressed() { 
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
    if (drawer.isDrawerOpen(GravityCompat.START)) { 
     drawer.closeDrawer(GravityCompat.START); 
    } else { 
     super.onBackPressed(); 
    } 
} 

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

//settings-ზე დაჭერის activity 
@Override 
public boolean onOptionsItemSelected(MenuItem item) { 
    int id = item.getItemId(); 

    if (id == R.id.action_settings) { 
     ArrayList<String> roomNameList = new ArrayList<>(); 
     for (Room r : roomList) { 
      roomNameList.add(r.getName()); 
     } 
     Intent intent = new Intent(MainActivity.this, SettingsActivity.class); 
     intent.putExtra("roomlist", roomNameList); 
     startActivity(intent); 
    } 
    if (id == R.id.action_log_out) { 
     Intent intent = new Intent(MainActivity.this, LoginActivity.class); 
     startActivity(intent); 
    } 
    return super.onOptionsItemSelected(item); 
} 


//მენიუდან არჩეული ოთახის განრიგის გამოტანა 
@SuppressWarnings("StatementWithEmptyBody") 
@Override 
public boolean onNavigationItemSelected(MenuItem item) { 
    for (Room r : roomList) { 
     if (item.getTitle().equals(r.getName())) { 
      bookingList = r.getBookingList(); 
      recAdapterBooking = new RecAdapterBooking(bookingList, MainActivity.this); 
      recyclerView.setAdapter(recAdapterBooking); 
      setTitle(r.getName()); 
      room = r; 
      break; 
     } 
    } 
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout); 
    drawer.closeDrawer(GravityCompat.START); 
    return true; 
} 

@Override 
public void onSaveInstanceState(Bundle state) { 
    super.onSaveInstanceState(state); 
    state.putParcelable(KEY_RECYCLER_STATE, recyclerView.getLayoutManager().onSaveInstanceState()); 

} 

protected void onRestoreInstanceState(Bundle state) { 
    super.onRestoreInstanceState(state); 

    // Retrieve list state and list/item positions 
    if (state != null) 
     recyclerView.getLayoutManager().onRestoreInstanceState(state.getParcelable(KEY_RECYCLER_STATE)); 
} 


@Override 
public void onStop(){ 
    super.onStop(); 
    onSaveInstanceState(state); 
} 
@Override 
public void onRestart(){ 
    super.onRestart(); 
    onRestoreInstanceState(state); 
    } 
} 

Answer 1

Vérifier si faisceau est nul et si oui, initialiser.

@Override 
public void onSaveInstanceState(Bundle state) { 
if(state==null){ 
    state=new Bundle(); 
} 
    super.onSaveInstanceState(state); 
    state.putParcelable(KEY_RECYCLER_STATE, recyclerView.getLayoutManager().onSaveInstanceState()); 

}