Xamarin.Android中未选中RadioGroup按钮上的RadioButton

Question

Sometimes my RadioGroup buttons are not checked while selecting. I am using Xamarin.Android and I have about 15 RadioButtons in RadioGroup . What is strange is that the focus is always set on the RadioButton clicked, but sometimes the same RadioButton is not set as Checked after click. Here is the sample code I currently use:

radioGroup.CheckedChange += delegate
{
    var radioButton = FindViewById<RadioButton>(radioGroup.CheckedRadioButtonId);
    radioButton.Focusable = true;
    radioButton.FocusableInTouchMode = true;
    radioButton.RequestFocus();
    radioButton.Checked = true;
};

What can I do to mark each RadioButton as Checked everytime I select it? Thanks in advance.

Answer 1

What is strange is that the focus is always set on the RadioButton clicked, but sometimes the same RadioButton is not set as Checked after click.

Because GetFocus always comes first when you click on the RadioButton, thus the CheckedChange event never got triggered when you click on the RadioButton for the first time.

So the correct way to do that is to register the focusChange event for every RadioButton and set the radio button to checked in the focusChange event handler:

public class MainActivity : Activity
{
    RadioGroup radioGroup;
    protected override void OnCreate(Bundle bundle)
    {
        base.OnCreate(bundle);

        // Set our view from the "main" layout resource
        SetContentView (Resource.Layout.Main);
        radioGroup = FindViewById<RadioGroup>(Resource.Id.mGroup);

        //register focus change event for every sub radio button.
        for (int i = 0; i < radioGroup.ChildCount; i++)
        {
            var child=radioGroup.GetChildAt(i);
            if (child is RadioButton)
            {
                ((RadioButton)child).FocusChange += RadioButton_FocusChange;
            }
        }
    }


    private void RadioButton_FocusChange(object sender, Android.Views.View.FocusChangeEventArgs e)
    {
        //check if the radio button is the button that getting focus
        if (e.HasFocus){
            ((RadioButton)sender).Checked = true;
        }
    }
}