Question

我尝试执行以下教程：

namespace App1
{
    [Activity(Label = "App1", MainLauncher = true, Icon = "@drawable/icon")]
    public class MainActivity : Activity
    {
        int count = 1;

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

            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            // Get the latitude/longitude EditBox and button resources:
            EditText latitude = FindViewById<EditText>(Resource.Id.latText);
            EditText longitude = FindViewById<EditText>(Resource.Id.longText);
            Button button = FindViewById<Button>(Resource.Id.getWeatherButton);

            // When the user clicks the button ...
            button.Click += async (sender, e) => {

                // Get the latitude and longitude entered by the user and create a query.
                string url = "http://api.geonames.org/findNearByWeatherJSON?lat=" +
                         latitude.Text +
                         "&lng=" +
                         longitude.Text +
                         "&username=demo";

                // Fetch the weather information asynchronously, 
                // parse the results, then update the screen:
                JsonValue json = await FetchWeatherAsync(url);
                // ParseAndDisplay (json);
            };
        }

        // Gets weather data from the passed URL.
        private async Task<JsonValue> FetchWeatherAsync(string url)
        {
            // Create an HTTP web request using the URL:
            HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create(new Uri(url));
            request.ContentType = "application/json";
            request.Method = "GET";

            // Send the request to the server and wait for the response:
            using (WebResponse response = await request.GetResponseAsync())
            {
                // Get a stream representation of the HTTP web response:
                using (Stream stream = response.GetResponseStream())
                {
                    // Use this stream to build a JSON document object:
                    JsonValue jsonDoc = await Task.Run(() => JsonObject.Load(stream));
                    Console.Out.WriteLine("Response: {0}", jsonDoc.ToString());

                    // Return the JSON document:
                    return jsonDoc;
                }
            }
        }
    }
}

但是当我调试弹出窗口时会显示以下消息：“System.InvalidCastException：无法将类型'Android.Widget.EditText'的实例转换为'Android.Widget.Button'。”

我添加了主要的布局代码，因为Xamarin在编辑文本时显示了错误：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout
    android:orientation="horizontal"
    android:layout_marginTop="10dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_horizontal"
    android:id="@+id/latSection">
    <TextView
        android:text="Enter Latitude:"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="140dp"
        android:layout_height="40dp"
        android:gravity="right"
        android:id="@+id/latLabel" />
    <EditText
        android:text="47.7"
        android:layout_width="150dp"
        android:layout_height="50dp"
        android:id="@+id/latText"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_marginLeft="5dp" />
</LinearLayout>
<LinearLayout
    android:orientation="horizontal"
    android:layout_marginTop="10dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_horizontal"
    android:id="@+id/longSection">
    <TextView
        android:text="Enter Longitude:"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="140dp"
        android:layout_height="40dp"
        android:gravity="right"
        android:id="@+id/longLabel" />
    <EditText
        android:text="-122.5"
        android:layout_width="150dp"
        android:layout_height="50dp"
        android:id="@+id/longText"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_marginLeft="5dp" />
</LinearLayout>
<LinearLayout
    android:orientation="vertical"
    android:layout_marginTop="28dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:gravity="center_horizontal"
    android:id="@+id/getSection">
    <Button
        android:id="@+id/getWeatherButton"
        android:layout_width="300dp"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal"
        android:textAppearance="?android:attr/textAppearanceLarge"
        android:text="Get Weather" />
</LinearLayout>
<LinearLayout
    android:orientation="horizontal"
    android:layout_marginTop="30dp"
    android:layout_marginLeft="40dp"
    android:layout_marginRight="40dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/locSection">
    <TextView
        android:text="Location:"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="120dp"
        android:layout_height="30dp"
        android:gravity="left"
        android:id="@+id/locLabel" />
    <TextView
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="wrap_content"
        android:layout_height="60dp"
        android:gravity="left"
        android:id="@+id/locationText" />
</LinearLayout>
<LinearLayout
    android:orientation="horizontal"
    android:layout_marginTop="10dp"
    android:layout_marginLeft="40dp"
    android:layout_marginRight="40dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/tempSection">
    <TextView
        android:text="Temperature:"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="120dp"
        android:layout_height="30dp"
        android:gravity="left"
        android:id="@+id/tempLabel" />
    <TextView
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="wrap_content"
        android:layout_height="30dp"
        android:gravity="left"
        android:id="@+id/tempText" />
</LinearLayout>
<LinearLayout
    android:orientation="horizontal"
    android:layout_marginTop="10dp"
    android:layout_marginLeft="40dp"
    android:layout_marginRight="40dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/humidSection">
    <TextView
        android:text="Humidity:"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="120dp"
        android:layout_height="30dp"
        android:gravity="left"
        android:id="@+id/humidLabel" />
    <TextView
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="wrap_content"
        android:layout_height="30dp"
        android:gravity="left"
        android:id="@+id/humidText" />
</LinearLayout>
<LinearLayout
    android:orientation="horizontal"
    android:layout_marginTop="10dp"
    android:layout_marginLeft="40dp"
    android:layout_marginRight="40dp"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/condSection">
    <TextView
        android:text="Conditions:"
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="120dp"
        android:layout_height="30dp"
        android:gravity="left"
        android:id="@+id/condLabel" />
    <TextView
        android:text=""
        android:textAppearance="?android:attr/textAppearanceMedium"
        android:layout_width="wrap_content"
        android:layout_height="60dp"
        android:gravity="left"
        android:id="@+id/condText" />
</LinearLayout>

感谢您的帮助。

---- ----- EDIT

我完成了解决我的问题。

namespace App1
{
[Activity(Label = "App1", MainLauncher = true, Icon = "@drawable/icon")]
public class MainActivity : Activity
{

    private Button button;
    private EditText latitude;
    private EditText longitude;

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

        // Set our view from the "main" layout resource
        SetContentView(Resource.Layout.Main);

        // Get the latitude/longitude EditBox and button resources:
        latitude = FindViewById<EditText>(Resource.Id.latText);
        longitude = FindViewById<EditText>(Resource.Id.longText);
        button = FindViewById<Button>(Resource.Id.getWeatherButton);

Answer 1

将<Edittext>替换为<TextView>

latitude = FindViewById<TextView>(Resource.Id.latText);
longitude = FindViewById<TextView>(Resource.Id.longText);

无法将“Android.Widget.EditText”类型的实例转换为“Android.Widget.Button”类型

1 个答案: