Question

Th question: Can I re-use RadioButton objects over and over again in an child activity?

I have a parent activity and a child activity. In the child activity, I have a large number of radio button displayed in a UI. In order to provide databinding from the parent down to the child, I have created a class (below) which contains a collection of RadioButtons. To populate the child activity, I pass a reference to this class down to the child which then groups the radioButtons into RadioGroups and displays them. I do this because the checked status of each button is now automatically available in the parent class, without the need to transfer any data through bundles.

public class GeneralAttribute{
    Activity  mThis;
    public class Gender {         // Mutually exclusive members
        String      categoryDesc  = "Gender of user";
        RadioButton isUnspecified = initRadioButton("Unspecified", true);
        RadioButton isMale        = initRadioButton("Male"       , false);
        RadioButton isFemale      = initRadioButton("Female"     , false);
    } ;
    <....more subclasses....>
    RadioButton initRadioButton(String str, Boolean b) {   // Factory
        float cLayoutWeight = 0.5f;
        RadioButton rb = new RadioButton(mThis);
        rb.setText   (str);
        rb.setChecked(b);
        rb.setLayoutParams(new LinearLayout.LayoutParams(LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT, cLayoutWeight));
        return rb;
    }
    GeneralAttribute(Activity localThis){ // Constructor
        mThis = localThis;
        gender     = new Gender();
        handedness = new Handedness();
        location   = new Location();
    }
}

In the parent activity i have:

public class Parent(...)

   public GeneralAttribute mGeneralAttribute;              // Member class of RadioButtons
   public static SPIGestureLoggerActivity TopLevelActivity;// Reference to the parent activity

   public void onCreate(Bundle savedInstanceState) {
       TopLevelActivity = this;                            // Assign this to the reference
       mGeneralAttribute = new GeneralAttribute(this);     // Initialize the class of RBs
       startActivity(child);                               // Start the child

In the child activity i have this:

    radiogroup = new RadioGroup(this);
    radiogroup.setOrientation(RadioGroup.VERTICAL);
    radiogroup.addView(Parent.TopLevelActivity.mGeneralAttribute.gender.isUnspecified);
    radiogroup.addView(Parent.TopLevelActivity.mGeneralAttribute.gender.isMale);
    radiogroup.addView(Parent.TopLevelActivity.mGeneralAttribute.gender.isFemale);
    Parent.TopLevelActivity.mGeneralAttribute.gender.isUnspecified.setChecked(true);
    mLinearLayout.addView(radiogroup);

This works fine….the first time the child activity is displayed. The second time it is displayed I get an exception.
In summary, here is the chain of events:

• create the class of RadioButtons,
• pass them to the child,
• add them to a new RadioGroup
• collect user choices
• finish the child acitivty (which should destroy the RadioGroups)
• use the data in the parent,
• start the child activity again,
• attempt to add the RadioButtons to new RadioGroups…
  …Exception.

I can avoid this problem, if I null the class and reconstruct it. However, I would like to re-show the choices made from the first viewing with the second viewing.

Ideas:

• Are the radioButtons saving pointers to the non-existant RadioGroups from the first viewing?
• Is there a way to re-assign the view parent on each radio button in the class?

P.S. You may ask why I’m not using XML. For one, I will have 100+ of these radio buttons and I think it will be too painful to manage through XML. For another, I just like working programmatically on these things.

Answer 1

make sure you remove all the radiobuttons from the all radiogroups. Basically your right the radiobuttons are saving pointers to the non-existant raidogroups and no there isn’t isn’t a way to reassigned without calling removeAllViews on all the radiogroups. The best place to do that will be the onDestroy if your sure thats being called.