android เก็บค่าตัวแปร variable มีดึงค่าแบบ session ปะครับ พอมีตัวอย่างให้มั้ยครับ

public class Calc extends Activity {
    public static final String PREFS_NAME = "MyPrefsFile";

    @Override
    protected void onCreate(Bundle state){
       super.onCreate(state);
       . . .

       // Restore preferences
       SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
       boolean silent = settings.getBoolean("silentMode", false);
       setSilent(silent);
    }

    @Override
    protected void onStop(){
       super.onStop();

      // We need an Editor object to make preference changes.
      // All objects are from android.context.Context
      SharedPreferences settings = getSharedPreferences(PREFS_NAME, 0);
      SharedPreferences.Editor editor = settings.edit();
      editor.putBoolean("silentMode", mSilentMode);

      // Commit the edits!
      editor.commit();
    }
}

public class UserHelper {
	Context context;
	SharedPreferences sharedPerfs;
	Editor editor;
	
	// Prefs Keys
	static String perfsName = "UserHelper";
	static int perfsMode = 0;
	
	public UserHelper(Context context) {
		this.context = context;
		this.sharedPerfs = this.context.getSharedPreferences(perfsName, perfsMode);
		this.editor = sharedPerfs.edit();
	}
	
	public void createSession(String key) {
		editor.putBoolean("isLogin", true);
                editor.putString("userID", key);
                editor.commit();
	}
	
	public void deleteSession() {
		editor.clear();
		editor.commit();
	}
	
	public boolean isLogin() {
		return sharedPerfs.getBoolean("isLogin", false);
	}
	
	public String getUserID() {
		return sharedPerfs.getString("userID", null);
	}
}

UserHelper usrHelper = new UserHelper(this);

// Create Session
usrHelper.createSession(ID);

// Delete Session
usrHelper.deleteSession();

// Check Login
if (usrHelper.isLogin()) {

} else {

}

// Get UserID
usrHelper.getUserID()