Xamarin的ClassNotFoundException

Question

我是新来Xamarin并写了一个简单的应用程序，但它显示了以下错误

Unhandled Exception: 
Java.Lang.ClassNotFoundException: md5c178831cd46fc53bebc42cf953f78ced.SignupActivity 
occurred 

我对MainActivity代码：

using Android.App; 
using Android.Widget; 
using Android.OS; 

namespace AndroidApp1 
{ 
    [Activity(Label = "Hello Xamarin", MainLauncher = true)] 
    public class MainActivity : Activity 
    { 
     private Button loginButton; 
     private Button signupButton; 
     protected override void OnCreate(Bundle savedInstanceState) 
     { 
      base.OnCreate(savedInstanceState); 
      SetContentView(Resource.Layout.Main); 
      loginButton = (Button)FindViewById(Resource.Id.login_btn); 
      signupButton = (Button)FindViewById(Resource.Id.signup_btn); 
      signupButton.Click += delegate 
      { 
       StartActivity(typeof(SignupActivity)); 
      }; 
     } 
    } 
} 

而对于SignupActivity：

using System.Text; 
using Android.App; 
using Android.OS; 
using Android.Widget; 

namespace AndroidApp1 
{ 
    [Activity(Label = "SignupActivity")] 
    public class SignupActivity : Activity 
    { 
     private EditText nameField; 
     private EditText usernameField; 
     private EditText passwordField; 
     private EditText emailField; 
     private Button signup; 
     protected override void OnCreate(Bundle savedInstanceState) 
     { 
      base.OnCreate(savedInstanceState); 
      SetContentView(Resource.Layout.SignupLayout); 
      nameField = (EditText)FindViewById(Resource.Id.name); 
      usernameField = (EditText)FindViewById(Resource.Id.username); 
      emailField = (EditText)FindViewById(Resource.Id.email); 
      passwordField = (EditText)FindViewById(Resource.Id.password); 
      signup = (Button)FindViewById(Resource.Id.signup_btn); 
      signup.Click += delegate 
      { 
       StringBuilder sb = new StringBuilder(); 
       sb.AppendLine(nameField.Text); 
       sb.AppendLine(usernameField.Text); 
       sb.AppendLine(emailField.Text); 
       sb.AppendLine(passwordField.Text); 
       Toast.MakeText(this, sb.ToString(), ToastLength.Short).Show(); 
      }; 
     } 
    } 
} 

你能告诉我我的错在哪里？谢谢。

编辑： 清单文件

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
      package="AndroidApp1.AndroidApp1" 
      android:versionCode="1" 
      android:versionName="1.0"> 
    <uses-sdk android:minSdkVersion="21" /> 
    <application android:allowBackup="true" android:label="@string/app_name"> 
    </application> 
</manifest> 

Answer 1

这是一个已知的bug，清洁，再建项目，通常可以解决它。