在RecyclerView中滚动时，单选按钮会丢失值

Question

请帮我发现bug！我已经在这个问题上阅读了很多帖子，但我不能让我的工作。对我来说，看起来我正在按照其他解决方案这样做，但我错过了一些东西。

我使用recyclelerview将调查作为一个问题实现了3个可能的答案，其中每行都有一个带3个单选按钮的无线电组。

滚动单选按钮时会丢失其值，并且在unbind事件中不会再次设置。

public class MyQItem
{
    public int Id;
    public string Question;
    public int Value;

    public MyQItem(int id, string question)
    {
        Id = id;
        Question = question;
    }
}

internal class MyQFormAdapter : RecyclerView.Adapter
{
    private MyQItem[] mDataSource;

    public MyQFormAdapter(MyQItem[] mDataSource)
    {
        this.mDataSource = mDataSource;
    }

    public override int ItemCount => mDataSource.Length;

    public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
    {
        MyQViewHolder vh = holder as MyQViewHolder;

        vh.QuestionId.Text = mDataSource[position].Id.ToString();
        vh.Question.Text = mDataSource[position].Question;

        vh.Button1.CheckedChange -= Button1_CheckedChange;
        vh.Button2.CheckedChange -= Button2_CheckedChange;
        vh.Button3.CheckedChange -= Button3_CheckedChange;

        vh.Button1.Checked = mDataSource[position].Value == 1;
        vh.Button2.Checked = mDataSource[position].Value == 2;
        vh.Button3.Checked = mDataSource[position].Value == 3;

        vh.Button1.Tag = position;
        vh.Button2.Tag = position;
        vh.Button3.Tag = position;

        vh.Button1.CheckedChange += Button1_CheckedChange;
        vh.Button2.CheckedChange += Button2_CheckedChange;
        vh.Button3.CheckedChange += Button3_CheckedChange;
    }

    void Button1_CheckedChange(object sender, CompoundButton.CheckedChangeEventArgs e) => SetChecked((RadioButton)sender, 1, e.IsChecked);
    void Button2_CheckedChange(object sender, CompoundButton.CheckedChangeEventArgs e) => SetChecked((RadioButton)sender, 2, e.IsChecked);
    void Button3_CheckedChange(object sender, CompoundButton.CheckedChangeEventArgs e) => SetChecked((RadioButton)sender, 3, e.IsChecked);

    void SetChecked(RadioButton btn, int value, bool isChecked)
    {
        if (!isChecked)
            return;

        var position = (int)btn.Tag;
        mDataSource[position].Value = value;
    }

    public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
    {
        View itemView = LayoutInflater.From(parent.Context).Inflate(Resource.Layout.MyQItemLayout, parent, false);

        MyQViewHolder vh = new MyQViewHolder(itemView);
        return vh;
    }
}

[Activity(Label = "MyQEditActivity")]
public class MyQEditActivity : Activity
{
    MyQItem[] mDataSource = new MyQItem[] { 
        new MyQItem(1, "Lorem Ipsum"),
        new MyQItem(2, "Lorem Ipsum"),
        new MyQItem(3, "Lorem Ipsum"),
        new MyQItem(4, "Lorem Ipsum"),
        new MyQItem(5, "Lorem Ipsum"),
        new MyQItem(6, "Lorem Ipsum"),
        new MyQItem(7, "Lorem Ipsum"),
        new MyQItem(8, "Lorem Ipsum"),
        new MyQItem(9, "Lorem Ipsum"),
        new MyQItem(10, "Lorem Ipsum"),
        new MyQItem(11, "Lorem Ipsum"),
        new MyQItem(12, "Lorem Ipsum"),
    };

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        SetContentView(Resource.Layout.MyQEditLayout);

        var recyclerView = FindViewById<RecyclerView>(Resource.Id.recyclerView);
        recyclerView.SetLayoutManager(new LinearLayoutManager(this));
        recyclerView.SetAdapter(new MyQFormAdapter(mDataSource));
    }

}

public class MyQViewHolder : RecyclerView.ViewHolder
{
    public TextView QuestionId { get; private set; }
    public TextView Question { get; private set; }
    public RadioButton Button1 { get; private set; }
    public RadioButton Button2 { get; private set; }
    public RadioButton Button3 { get; private set; }

    public MyQViewHolder(View itemView) : base(itemView)
    {
        QuestionId = itemView.FindViewById<TextView>(Resource.Id.MyQuestionId);
        Question = itemView.FindViewById<TextView>(Resource.Id.MyQuestion);

        Button1 = itemView.FindViewById<RadioButton>(Resource.Id.noButton);
        Button2 = itemView.FindViewById<RadioButton>(Resource.Id.someButton);
        Button3 = itemView.FindViewById<RadioButton>(Resource.Id.yesButton);
    }
}

Answer 1

您可以将侦听器添加到RadioGroup并修改您的适配器，如下所示：

class MyQFormAdapter : RecyclerView.Adapter, RadioGroup.IOnCheckedChangeListener
{
    private MyQItem[] mDataSource;
    public MyQFormAdapter(MyQItem[] mDataSource)
     {
      this.mDataSource = mDataSource;
     }


    public override int ItemCount => mDataSource.Length;

    public override void OnBindViewHolder(RecyclerView.ViewHolder holder, int position)
    {
        MyQViewHolder vh = holder as MyQViewHolder;

       // cancel the listener to prevent RadioGroup from displaying confusing key codes
        vh.Group.SetOnCheckedChangeListener(null);
        vh.Group.ClearCheck();
        vh.Group.Tag = position;

        switch (mDataSource[position].Value)
        {
            case 1:
                vh.Group.Check(Resource.Id.noButton);
                break;
            case 2:
                vh.Group.Check(Resource.Id.someButton);
                break;
            case 3:
                vh.Group.Check(Resource.Id.yesButton);
                break;

        }
        vh.QuestionId.Text = mDataSource[position].Id.ToString();
        vh.Question.Text = mDataSource[position].Question;
        vh.Group.SetOnCheckedChangeListener(this);
    }
    public override RecyclerView.ViewHolder OnCreateViewHolder(ViewGroup parent, int viewType)
    {

        View itemView = LayoutInflater.From(parent.Context).Inflate(Resource.Layout.MyQItemLayout, parent,false);

        MyQViewHolder vh = new MyQViewHolder(itemView);
        return vh;
    }

    public class MyQViewHolder : RecyclerView.ViewHolder
    {
        public TextView QuestionId { get; private set; }
        public TextView Question { get; private set; }

        public RadioGroup Group { get; private set; }
        public MyQViewHolder(View itemView) : base(itemView)
        {
            QuestionId = itemView.FindViewById<TextView>(Resource.Id.MyQuestionId);
            Question = itemView.FindViewById<TextView>(Resource.Id.MyQuestion);
            Group = itemView.FindViewById<RadioGroup>(Resource.Id.radiogroup);
        }
    }

    public void OnCheckedChanged(RadioGroup @group, int checkedId)
    {
        switch (checkedId)
        {
            case Resource.Id.noButton:
                mDataSource[(int) @group.Tag].Value = 1;
                break;
            case Resource.Id.someButton:
                mDataSource[(int)@group.Tag].Value = 2;
                break;
            case Resource.Id.yesButton:
                mDataSource[(int)@group.Tag].Value = 3;
                break;
        }
    }
}