Simple SharedPreferences in Android

Question

I'm having a problem, and I already tried everything I found on this site, it's not helping, so I'm asking this question myself.

my code is:

public class MyActivity extends Activity{

    protected PositionSense positionSense;
    protected Preferences preferences;
    String IP;
    String ID;

@Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        positionSense = new PositionSense(this, null);
        SharedPreferences settings = getSharedPreferences("preferences", 0);
        IP = settings.getString("ip", "http://192.168.1.3:8080/servlet");
        ID = settings.getString("id", "USER");
    }

Later on, I use these variables in a background running thread that contacts the servlet and sends some info (including position and ID of the user which is saved in preferences)

I'm not posting all of that because I don't want to clog up the thread more than necessary (but if it is needed, I will post it all)

In any case, it doesn't work and it gives me the following error log:

09-14 16:47:20.854: WARN/dalvikvm(552): threadid=1: thread exiting with uncaught exception (group=0x409c01f8)
09-14 16:47:20.884: ERROR/AndroidRuntime(552): FATAL EXCEPTION: main
        java.lang.IllegalStateException: Could not execute method of the activity
        at android.view.View$1.onClick(View.java:3044)
        at android.view.View.performClick(View.java:3511)
        at android.view.View$PerformClick.run(View.java:14105)
        at android.os.Handler.handleCallback(Handler.java:605)
        at android.os.Handler.dispatchMessage(Handler.java:92)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4424)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)
        Caused by: java.lang.reflect.InvocationTargetException
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at android.view.View$1.onClick(View.java:3039)
        ... 11 more
        Caused by: java.lang.NullPointerException
        at com.moodswings.MoodSwingsActivity.clickHappy(MoodSwingsActivity.java:94)
        ... 14 more

I don't know what to do about it.

Can someone give me the SIMPLEST possible way to save 2 strings in preferences in one activity that are used in some other activity within the same application? It's supposed to be really simple, but I simply cannot make it work, and I'm nearing my deadline. Thanks!

Answer 1

To save to shared preferences you can try:

String ip = "192.168.1.1";
SharedPreferences prefs = getSharedPreferences("IP", Context.MODE_PRIVATE);
prefs.edit().putString("Sample IP", ip).commit();

To get the information from the shared preferences you can try:

String newIP = prefs.getString("Sample IP");//You can also place a default value if needed; to bypass the null character.

Now to pass them into activities you can try doing an intent call like below

**Activity One
Intent intent = new Intent(getApplicationContext(),SecondActivity.class);
intent.putExtra("IP",newIp);  
startActivity(intent);

**Activity Two
Bundle extras = intent.getExtras(); 
String tmp = extras.getString("IP");

Also you can use this link to reference.