RecyclerView OnClick 在其他位置更改项目

Question

我在 RecyclerView 中有一个字符串列表。我需要能够单击列表中的项目并将背景更改为黄色。我可以单击一个项目并更改背景，但是当我向下滚动列表时，我看到列表中的另一个项目的背景也变成了黄色？

我尝试了许多不同的方法来实现这一点。我尝试设置一个界面，点击 ViewHolder 等。

我的代码如下。

活动：

[Activity(Label = "PregnancyListActivity")]
public class PregnancyListActivity : Activity
{
    RecyclerView mRecyclerView;
    RecyclerView.LayoutManager mLayoutManager;
    PregnantAnimalAdapter mAdapter;

    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);
        SetContentView(Resource.Layout.PregnancyListLayout);

        mRecyclerView = FindViewById<RecyclerView>(Resource.Id.recyclerView);

        // Plug in the linear layout manager:
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.SetLayoutManager(mLayoutManager);

        // Plug in my adapter:
        mAdapter = new PregnantAnimalAdapter();
        mAdapter.ItemClick += MAdapter_ItemClick;
        mRecyclerView.SetAdapter(mAdapter);
    }
}

查看持有人

[Activity(Label = "PregnantAnimalViewHolder")]
public class PregnantAnimalViewHolder : RecyclerView.ViewHolder
{
    public LinearLayout mBackground { get; private set; }
    public TextView mAnimalTag { get; private set; }

    public PregnantAnimalViewHolder(View itemView) : base(itemView)
    {
        // Locate and cache view references:
        mBackground = itemView.FindViewById<LinearLayout>(Resource.Id.pregnancyBackground);
        mAnimalTag = itemView.FindViewById<TextView>(Resource.Id.animalTag);

    }
}

适配器：

public class PregnantAnimalAdapter : RecyclerView.Adapter
{
public PregnantAnimalAdapter pregnantAnimalAdapter;
public List<PregAnimals> mAnimals;

public PregnantAnimalAdapter()
{
    mAnimals = new List<PregAnimals>{
        new PregAnimals("111", false),
        new PregAnimals("112", false),
        new PregAnimals("113", false),
        new PregAnimals("114", false),
        new PregAnimals("115", false),
        new PregAnimals("221", false),
        new PregAnimals("222", false),
        new PregAnimals("223", false),
        new PregAnimals("224", false),
        new PregAnimals("225", false),
        new PregAnimals("331", false),
        new PregAnimals("332", false),
        new PregAnimals("333", false),

        new PregAnimals("444", false),
        new PregAnimals("443", false),
        new PregAnimals("554", false),
        new PregAnimals("4435", false),
        new PregAnimals("4234", false),
        new PregAnimals("543", false),
        new PregAnimals("3452", false),
        new PregAnimals("3321", false),
        new PregAnimals("6676", false),
        new PregAnimals("4367", false)
    };
}

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

    PregnantAnimalViewHolder vh = new PregnantAnimalViewHolder(itemView);

    vh.mBackground.Click += (object sender, EventArgs e) => {
        mAnimals[vh.LayoutPosition].Preg = true;
    };

    return vh;
}



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

    vh.mAnimalTag.Text = mAnimals[position].Tag;
    if (mAnimals[position].Preg == true)
    {
        vh.mBackground.SetBackgroundResource(RecordMilk.Resource.Color.munster_yellow);
    }

}



public override int ItemCount
{
    get { return mAnimals.Count; }
}
}

public class PregAnimals
{
    public string Tag { get; set; }
    public bool Preg { get; set; }

    public PregAnimals(string tag, bool preg)
    {
        Tag = tag;
        Preg = preg;
    }

}

我很困惑为什么它不只是在列表中设置项目。任何帮助将不胜感激。

提前致谢！

Answer 1

尝试在适配器中添加这一行：

@Override
public int getItemViewType(int position) {
    return position; 
}

Answer 2

问题是 RecyclerView 正在做它应该做的 - 回收视图。您更改了颜色的 View 正在被重新用于新项目，但其颜色仍处于选中状态。

假设您希望选择保留，您需要跟踪选择了哪一个，并在 OnBindViewHolder 中将背景颜色设置为选中或未选中的颜色。否则只需将背景设置为未选中即可。

此外，您可以创建一个 StateListDrawable 并将其分配给具有选中/未选中状态的背景，因此您只需将视图的状态设置为选中即可。优点是它将所有样式保存在资源中。

public class PregnantAnimalViewHolder : RecyclerView.ViewHolder
{
    public LinearLayout mBackground { get; private set; }
    public TextView mAnimalTag { get; private set; }
    public bool Selected {get;set;}
    public int position {get;set;}

    public PregnantAnimalViewHolder(View itemView) : base(itemView)
    {
        // Locate and cache view references:
        mBackground = itemView.FindViewById<LinearLayout>(Resource.Id.pregnancyBackground);
        mAnimalTag = itemView.FindViewById<TextView>(Resource.Id.animalTag);

    }
}

然后在 OnBindViewHolder 中

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

    vh.mAnimalTag.Text = mAnimals[position];
    vh.position = position;
    vh.View.SetBackgroundResource(
         vh.Selected?Resource.Color.munster_yellow:Resource.Color.whatever);

    // or vh.View.SetSelected(vh.Selected) for using StateListDrawable as the background

}