Question

I’ve encountered a problem after I set set my text in Android. Well the scenario goes like this:

I use putExtra from one of my classes then starts intent. on the Second class I declared a String variable which will catch the Extra the code is:

String playername = " ";
String emailaddress = " ";

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.gamepage);

    playername = getIntent().getStringExtra("pname");
    Log.v(TAG, "Player name set to : " + playername);
    emailaddress = getIntent().getStringExtra("eadd");
    Log.v(TAG, "Email set to : " + emailaddress);
    TextView playerName = (TextView)findViewById(R.id.playerName);
        Log.v(TAG, "view fetched");

I used Logs to track the passing of data and it seems to work fine but after adding the part of playerName.setText(playername);

the problem now begins and error logs shows this:

 11-22 16:30:50.271: WARN/dalvikvm(4621): threadid=1: thread exiting with uncaught exception (group=0x4001d800)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621): FATAL EXCEPTION: main
11-22 16:30:50.397: ERROR/AndroidRuntime(4621): java.lang.RuntimeException: Unable to start activity ComponentInfo{arc.android.memorygame/arc.android.memorygame.SetGameScreen}: java.lang.NullPointerException
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.app.ActivityThread.access$2300(ActivityThread.java:125)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.os.Handler.dispatchMessage(Handler.java:99)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.os.Looper.loop(Looper.java:123)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.app.ActivityThread.main(ActivityThread.java:4627)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at java.lang.reflect.Method.invokeNative(Native Method)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at java.lang.reflect.Method.invoke(Method.java:521)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at dalvik.system.NativeStart.main(Native Method)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621): Caused by: java.lang.NullPointerException
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at arc.android.memorygame.SetGameScreen.onCreate(SetGameScreen.java:29)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
11-22 16:30:50.397: ERROR/AndroidRuntime(4621):     ... 11 more

Is there’s a problem with my code? why does it returns Null Pointer Exception?

Answer 1

Probably playername is null after this line:

playername = getIntent().getStringExtra("pname");

getStringExtra will return null if no string value is found.

Try something like this:

playername = getIntent().getStringExtra("pname");
if (playername == null)
    playername = "some default value";

Later edit:

If you are absolutely certain that playername is not null at that point, it means that findViewById returned null for some reason (a typo, an error in your xml or whatever).

And, by the way, if you have logs and can check for yourself if a variable is null or not, why don’t you do it instead of asking? A NullPointerException is not that hard to track down, especially when you only have a few variables.