NullPointerException while Preferences deleting which were added dynamically

Question

I need to add Preferences dynamically to my PreferenceActivity and I do it like this:

mFilterShow = (PreferenceScreen)getPreferenceScreen().findPreference("orderScreen");


public void assignmentFieldsAdd()
{
    CheckBoxPreference cb1 = new CheckBoxPreference(this);
    cb1.setTitle("Detailed explanation " + "\r\n" +"required");
    cb1.setKey("assign1");
    CheckBoxPreference cb2 = new CheckBoxPreference(this);
    cb2.setTitle("Shoot exclusive video");
    cb1.setKey("assign2");
    CheckBoxPreference cb3 = new CheckBoxPreference(this);
    cb1.setKey("assign3");
    cb3.setTitle("Shoot common video");
     mFilterShow.addPreference(cb1);
     mFilterShow.addPreference(cb2);
     mFilterShow.addPreference(cb3); 
}

and then, I need to delete it on some event. When I call

  public void assignmentFieldsDelete()
    {

        mFilterShow.removePreference(mFilterShow.findPreference("assign1"));
        mFilterShow.removePreference(mFilterShow.findPreference("assign2"));
        mFilterShow.removePreference(mFilterShow.findPreference("assign3"));

    }

I get an

 02-05 18:14:50.159: E/AndroidRuntime(15259): FATAL EXCEPTION: main
 java.lang.NullPointerException
    at com.assignmentexpert.AssignmentPref.assignmentFieldsDelete(AssignmentPref.java:175)
    at com.assignmentexpert.AssignmentPref$2.onPreferenceChange(AssignmentPref.java:97)
    at android.preference.Preference.callChangeListener(Preference.java:756)
    at android.preference.ListPreference.onDialogClosed(ListPreference.java:219)
    at android.preference.DialogPreference.onDismiss(DialogPreference.java:389)
    at android.app.Dialog$ListenersHandler.handleMessage(Dialog.java:1047)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:123)
    at android.app.ActivityThread.main(ActivityThread.java:3687)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
    at dalvik.system.NativeStart.main(Native Method)

so it can't find preference which I created dynamically. The same thing occurs when I simply want to call getPreferenceScreen().findPreference("assign1").getTitle(); How can I resolve this?

Answer 1

I didn't find accurate solution to my question. It's quite weird that I can't delete or even find Preferences which I added dynamically to my PreferenceScreen. In both cases I've got NullPointerException.

But I find solution which solved my issue. I created 2 separated xml preferences with all required elements. I add and remove them on corresponding events.