System.InvalidCastException：Xamarin Android

Question

我正在开发Xamarin Android。我创建了自己的自定义Spinner，其中包含Image和TextView。在我的活动中，我需要获取Spinner当前所选项目的值，但我得到System.InvalidCastException: Specified cast is not valid.我的代码如下：

CustomSpinner.axml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:background="@color/splash_background"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="match_parent">
<ImageView
    android:src="@drawable/thinking_icon"
    android:layout_width="20dp"
    android:layout_height="20dp"
    android:id="@+id/FeedTypeImage" />
<TextView
    android:text="Thinking of"
    android:textAppearance="?android:attr/textAppearanceMedium"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:textColor="@color/Black"
    android:id="@+id/FeedTypeText"
    android:layout_marginLeft="10dp" />

CustomSpinnerAdapter.cs

public class CustomSpinnerAdapter : BaseAdapter
{
    private Context c;
    private JavaList<FeedType> feedTypes;
    private LayoutInflater inflater;

    public CustomSpinnerAdapter(Context c, JavaList<FeedType> feedTypes)
    {
        this.c = c;
        this.feedTypes = feedTypes;
    }

    public override int Count
    {
        get { return feedTypes.Size(); }
    }

    //compiler throws InvalidCast Exception here
    public override Object GetItem(int position)
    {
        return feedTypes.Get(position);
    }

    public override long GetItemId(int position)
    {
        return position;
    }

    public override View GetView(int position, View convertView, ViewGroup parent)
    {
        if (inflater == null)
            inflater = (LayoutInflater)c.GetSystemService(Context.LayoutInflaterService);

        if (convertView == null)
            convertView = inflater.Inflate(Resource.Layout.CustomSpinner, parent, false);

        TextView feedTitle = convertView.FindViewById<TextView>(Resource.Id.FeedTypeText);
        ImageView feedImage = convertView.FindViewById<ImageView>(Resource.Id.FeedTypeImage);

        feedTitle.Text = feedTypes[position].Title;
        feedImage.SetImageResource(feedTypes[position].FeedTypeImage);


        return convertView;
    }
}

MyActivity.cs

 private Spinner spinnerPostType;
 spinnerPostType = FindViewById<Spinner>(Resource.Id.spinner);
 spinnerAdapter = new CustomSpinnerAdapter(this, feedType);
 spinnerPostType.Adapter = spinnerAdapter;
 string selectedSpinnerText = spinnerPostType.SelectedItem.ToString();

Answer 1

而不是覆盖GetItem方法尝试覆盖索引器

public override FeedType this[int position] {
    get {
        return feedTypes.Get(position);
    }
}

Answer 2

试试这个：

//Get the selected position in your spinner
int position  = spinnerPostType.SelectedItemPostition;
//Get the title of the selected item
string selectedSpinnerText = feedType[position].Title;

我希望这会有所帮助：）