java.lang.NullPointerException: bash de invocar el método virtual en una referencia de objeto nulo

Intento guardar el nombre del jugador en una preferencia compartida y hacer que se muestre en otra actividad obteniéndolo de nuevo en preferencia compartida, pero la aplicación se cuelga.

EXCEPCIÓN FATAL: principal

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 

Códigos:

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); } 

El locking de tu aplicación está en:

 welcomePlayer.setText("Welcome Back, " + String.valueOf(mPlayer.getName(this)) + " !"); 

porque mPlayer=null .

Olvidaste inicializar Player mPlayer en tu Actividad de Juego de Juego.

 mPlayer = new Player(context,"");