How to return to main activity from onDialogClosed method in DialogPreference class

Question

I have defined custom preference class that extends Dialogpreference class for the settings activity,

public class YesNoPreference extends DialogPreference {

private boolean mWasPositiveResult;
    DashboardActivity dashboardActivity;
Context prefContext;

public YesNoPreference(Context context, AttributeSet attrs, int defStyle) {
    super(context, attrs, defStyle);
    userSession = new UserSessions(context);
    prefContext = context;
}

@Override
protected void onDialogClosed(boolean positiveResult) {
    super.onDialogClosed(positiveResult);

    if (callChangeListener(positiveResult)) {
        setValue(positiveResult);

        /* Unset all user shared preferences */
        userSession.unsetSessionData();

    try {   
    dashboardActivity = new DashboardActivity();
    //dashboardActivity.loginScreen();
    Intent dashboard = new Intent(prefContext, DashboardActivity.class);
    dashboardActivity.startActivity(dashboard);

     } catch (Exception e) {
     e.printStackTrace();
     }
    }
}

/**
 * Sets the value of this preference, and saves it to the persistent store
 * if required.
 * 
 * @param value The value of the preference.
 */
public void setValue(boolean value) {
    mWasPositiveResult = value;

    persistBoolean(value);

    notifyDependencyChange(!value);
}

Am using the dialogprefernce to logout a user from the application. So if the user selects 'OK', the sharedprefernces are to be unset and then the user should be directed to the login page.

I tried creating a function in the Activity class and then calling it in this class. Also used Intent class, but the execution stops at

dashboardActivity.startActivity(dashboard);

and generates a Null Pointer exception.

Please help me, to find the solution.

public class SettingsActivity extends Activity {

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

    // Display the fragment as the main content.
    getFragmentManager().beginTransaction()
            .replace(android.R.id.content, new SettingsFragment())
            .commit();
   }

}

public class SettingsFragment extends PreferenceFragment {

@Override
    public void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);

       // Load the preferences from an XML resource
       addPreferencesFromResource(R.xml.pref_settings);
   }
}

score 1 · Accepted Answer · answered Mar 28 '13 at 12:33

1

use

prefContext.startActivity(dashboard);

instead of

dashboardActivity.startActivity(dashboard);

to access startActivity method. currently you are trying to create instance of DashboardActivity Activity for accessing startActivity method. use prefContext for starting Activity

answered Mar 28 '13 at 12:33

ρяσѕρєя K

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thanks a lot... that worked. Can you please also help me understand why do we have to use Context object and not activity object ?? Thanks in advance – Mamta Mar 28 '13 at 12:47
@Mamta : you are getting `NullPointerexception` because activity is not same as normal java class. like in java we create an object for accessing any method from an class. never try to create an object of Activity before this always throw `NullPointerexception` if Activity is not running as in your case DashboardActivity is not running. – ρяσѕρєя K Mar 28 '13 at 12:50

How to return to main activity from onDialogClosed method in DialogPreference class

1 Answers1