Question

我刚开始探索Spinner控件。我已经实现了我想要的东西但只缺少最后一步。这是我到目前为止所做的。

这个例子我有一个非常简单的类：

[Serializable]
public class Merchant
{
    public Int64 MerchantId { get; set; }
    public String ShopName { get; set; }

    public override string ToString()
    {
        return ShopName;
    }
}

这是我放置Spinner的轴：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="1280dip"
    android:layout_height="800dip">
    <TextView
        android:text="Select a merchant:"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:id="@+id/lblSelect"
        android:layout_marginLeft="30dip"
        android:layout_marginTop="30dip"
        android:textSize="42dip" />
    <Spinner
        android:id="@+id/spinMerchant"
        android:layout_width="1000dip"
        android:layout_height="wrap_content"
        android:layout_below="@id/lblSelect"
        android:prompt="@string/spinner_prompt"
        android:layout_centerHorizontal="true"
        android:minHeight="20dip" />
</RelativeLayout>

我的代码是：

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

        // Create your application here
        this.SetContentView(Resource.Layout.MerchantSelect);

        List<Merchant> lstMerchant = new List<Merchant> ();
        lstMerchant.Add (new Merchant() { ShopName = "First Shop", MerchantId = 11 });
        lstMerchant.Add (new Merchant() { ShopName = "Second Shop", MerchantId = 12 });

        Spinner spinner = this.FindViewById<Spinner>(Resource.Id.spinMerchant);
        ArrayAdapter adapter = new ArrayAdapter (this, Android.Resource.Layout.SimpleSpinnerItem, lstMerchant);
        spinner.ItemSelected += new EventHandler<AdapterView.ItemSelectedEventArgs> (spinner_ItemSelected);

        spinner.Adapter = adapter;
    }

    private void spinner_ItemSelected (object sender, AdapterView.ItemSelectedEventArgs e)
    {
        Spinner spinner = (Spinner)sender;
        //Merchant merch = (Merchant)spinner.SelectedItem;
        string toast = string.Format ("Selected text is {0}", spinner.GetItemAtPosition (e.Position));
        Toast.MakeText (this, toast, ToastLength.Long).Show ();
    }

我想在选择后立即获取所选文本及其背后的ID。我通过spinner.GetItemAtPosition (e.Position)得到了文字，但我似乎无法找到能给我ID的任何内容。如果我尝试Merchant merch = (Merchant)spinner.SelectedItem;，我会收到例外：Cannot convert type 'Java.Lang.Object' to 'Merchant'。

请告诉我如何实现。

感谢。

Answer 1

微调器只知道文本，因为这是你ToString()方法中的内容。提供微调器数据的适配器不知道它正在处理Merchant个对象。要访问实际的商家对象，您必须让List<Merchant> lstMerchant成为您班级的成员。

然后更改您的选择处理程序：

private void spinner_ItemSelected (object sender, AdapterView.ItemSelectedEventArgs e)
    {
        Spinner spinner = (Spinner)sender;
       // Get the ID from your model.
        Merchant merch = this.lstMerchant[e.Position];
        var id = merch.MerchantId;
        string toast = string.Format ("Selected text is {0}", spinner.GetItemAtPosition (e.Position));
        Toast.MakeText (this, toast, ToastLength.Long).Show ();
    }

Monodroid中的微调控制 - 获取选择的ID和文本

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