SharedPreference - Null Pointer Exception

Question

I am trying to save something to SharedPreferences using this code below:

public class SignupActivity extends Activity {

    String str;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.signup);

        str = PreferenceManager.getDefaultSharedPreferences(this).getString(
                "signedUp", null);

        SharedPreferences app_preferences = PreferenceManager
                .getDefaultSharedPreferences(this);

        String text = app_preferences.getString("signedUp", null);

        if(str.equals("YES")){
            startActivity(new Intent("com.mobi.job.scout.MyTabActivity"));
        }

        markAsSignedUp();

    }

    public void markAsSignedUp() {
        SharedPreferences.Editor localEditor = PreferenceManager
                .getDefaultSharedPreferences(getBaseContext()).edit();
        localEditor.putString("signedUp", "YES");
        localEditor.commit();
        Log.d("Signed Up!", ":)");
    }

}

I have read and followed some tutorials on the internet but I'm getting the error below. This is the logcat:

10-23 01:47:27.061: E/AndroidRuntime(408): FATAL EXCEPTION: main
10-23 01:47:27.061: E/AndroidRuntime(408): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.mobi.job.scout/com.mobi.job.scout.SignupActivity}: java.lang.NullPointerException
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2663)
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2679)
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.app.ActivityThread.access$2300(ActivityThread.java:125)
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2033)
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.os.Handler.dispatchMessage(Handler.java:99)
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.os.Looper.loop(Looper.java:123)
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.app.ActivityThread.main(ActivityThread.java:4627)
10-23 01:47:27.061: E/AndroidRuntime(408):  at java.lang.reflect.Method.invokeNative(Native Method)
10-23 01:47:27.061: E/AndroidRuntime(408):  at java.lang.reflect.Method.invoke(Method.java:521)
10-23 01:47:27.061: E/AndroidRuntime(408):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
10-23 01:47:27.061: E/AndroidRuntime(408):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
10-23 01:47:27.061: E/AndroidRuntime(408):  at dalvik.system.NativeStart.main(Native Method)
10-23 01:47:27.061: E/AndroidRuntime(408): Caused by: java.lang.NullPointerException
10-23 01:47:27.061: E/AndroidRuntime(408):  at com.mobi.job.scout.SignupActivity.onCreate(SignupActivity.java:28)
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1047)
10-23 01:47:27.061: E/AndroidRuntime(408):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2627)
10-23 01:47:27.061: E/AndroidRuntime(408):  ... 11 more

Please let me know what is wrong with the code I am using, I always end up getting force close. Thanks

Flynn81 · Accepted Answer · 2012-10-23 01:58:22Z

8

str = PreferenceManager.getDefaultSharedPreferences(this).getString(
                "signedUp", null);

Your variable str is null because a value for "signedUp" has not had a value set before. Check for null in your if statement.

if(str != null && str.equals("YES")){

If will not continue past str != null if it is true.

answered Oct 23, 2012 at 1:58

Flynn81

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2 Comments

Jason Hessley Over a year ago

You could also change the default return value of getString from null to an empty String ""

Flynn81 Over a year ago

Good point. Ideally you'd like to use a constant value for the default value for the preference, i.e. private static final String DEFAULT_SIGNEDUP_VALUE = "", or in my example = null. Either way would work.

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