java lang NullPointerException Attempt to invoke virtual method on a null object reference

Question

I am trying to save player s name in shared preference and make it display in another activity by getting it again in shared preference but my app crash   FATAL EXCEPTION  main   Process  plp cs4b thesis drawitapp  PID  1970  java lang RuntimeException  Unable to start activity ComponentInfo plp cs4b thesis drawitapp plp cs4b thesis drawitapp PlayGame   java lang NullPointerException  Attempt to invoke virtual method  java lang String plp cs4b thesis drawitapp Player getName    on a null object reference     at android app ActivityThread performLaunchActivity ActivityThread java 2298      at android app ActivityThread handleLaunchActivity ActivityThread java 2360      at android app ActivityThread access 800 ActivityThread java 144      at android app ActivityThread H handleMessage ActivityThread java 1278      at android os Handler dispatchMessage Handler java 102      at android os Looper loop Looper java 135      at android app ActivityThread main ActivityThread java 5221      at java lang reflect Method invoke Native Method      at java lang reflect Method invoke Method java 372      at com android internal os ZygoteInit MethodAndArgsCaller run ZygoteInit java 899      at com android internal os ZygoteInit main ZygoteInit java 694   Caused by  java lang NullPointerException  Attempt to invoke virtual method  java lang String plp cs4b thesis drawitapp Player getName    on a null object reference     at plp cs4b thesis drawitapp PlayGame onCreate PlayGame java 20      at android app Activity performCreate Activity java 5933      at android app Instrumentation callActivityOnCreate Instrumentation java 1105      at android app ActivityThread performLaunchActivity ActivityThread java 2251          10 more   Codes   Player java  public class Player    private Context context  private SharedPreferences prefSettingsU  private SharedPreferences Editor prefEditorU  private static final int PREFERENCE MODE PRIVATE   0  private static final String MY UNIQUE PREF FILE    DrawItApp    public Player Context context  String name        this context   context      saveName name      public void saveName String n        prefSettingsU   context getSharedPreferences MY UNIQUE PREF FILE  PREFERENCE MODE PRIVATE       prefEditorU   prefSettingsU edit        prefEditorU putString  keyName   n       prefEditorU commit       public String getName Context ctx        prefSettingsU   ctx getSharedPreferences MY UNIQUE PREF FILE  PREFERENCE MODE PRIVATE       String name   prefSettingsU getString  keyName    ANONYMOUS        return name      PlayGame java  public class PlayGame extends Activity    private TextView welcomePlayer  private ListView createdGames  private Player mPlayer    Override protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout play game        welcomePlayer    TextView  findViewById  R id tvPlayerName       welcomePlayer setText  Welcome Back      String valueOf mPlayer getName this                 createdGames    ListView  findViewById  R id listCreatedGames          adapter etc     createdGames setEmptyView findViewById  R id tvNoGames          PlayerName java  public class PlayerName extends Activity    private EditText playerName  private Player mPlayer  public static Context context    Override protected void onCreate Bundle savedInstanceState        super onCreate savedInstanceState       setContentView R layout player name       context   this      playerName    EditText  findViewById  R id etName       public void onC Confirm View btnclick        mPlayer   new Player context  String valueOf playerName getText            mPlayer saveName        Intent intent   new Intent PlayerName this  PlayGame class       startActivity intent      public void onC testShPref View btnclick        Intent intent   new Intent PlayerName this  PlayGame class       startActivity intent

User · Accepted Answer

Your app is crashing at    welcomePlayer setText  Welcome Back      String valueOf mPlayer getName this              because mPlayer null   You forgot to initialize Player mPlayer in your PlayGame Activity   mPlayer   new Player context

[java] java.lang.NullPointerException: Attempt to invoke virtual method on a null object reference

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