Xamarin AndroidX 遷移：應用程序啟動時崩潰（System.InvalidCastException：AndroidX.AppCompat.Widget.Toolbar）

Question

我最近將我的應用程序更新到 Xamarin Forms 5.0，因此更新到 AndroidX。 我升級了所有軟件包，它仍然引用舊的 Android 支持庫，並用 AndroidX 的等效引用替換了我的代碼中所有出現的 Android 支持庫引用。

但我的應用程序在啟動時不斷崩潰，但有以下例外：

[AndroidRuntime] android.runtime.JavaProxyThrowable: System.InvalidCastException: Unable to convert instance of type 'Android.Widget.LinearLayout' to type 'AndroidX.AppCompat.Widget.Toolbar'.
[AndroidRuntime]   at Java.Interop.JavaObjectExtensions.CastClass (Android.Runtime.IJavaObject instance, System.Type resultType) [0x0005d] in <1410c4afb1fd4823a12ecf897dd92287>:0 
[AndroidRuntime]   at Java.Interop.JavaObjectExtensions._JavaCast[TResult] (Android.Runtime.IJavaObject instance) [0x00052] in <1410c4afb1fd4823a12ecf897dd92287>:0 
[AndroidRuntime]   at Java.Interop.JavaObjectExtensions.JavaCast[TResult] (Android.Runtime.IJavaObject instance) [0x00000] in <1410c4afb1fd4823a12ecf897dd92287>:0 
[AndroidRuntime]   at Android.Runtime.Extensions.JavaCast[TResult] (Android.Runtime.IJavaObject instance) [0x00000] in <1410c4afb1fd4823a12ecf897dd92287>:0 
[AndroidRuntime]   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.OnCreate (Android.OS.Bundle savedInstanceState, Xamarin.Forms.Platform.Android.ActivationFlags flags) [0x00090] in <04c545f414d24a37af95d995791bb9a9>:0 
[AndroidRuntime]   at Xamarin.Forms.Platform.Android.FormsAppCompatActivity.OnCreate (Android.OS.Bundle savedInstanceState) [0x00000] in <04c545f414d24a37af95d995791bb9a9>:0 
[AndroidRuntime]   at MyAppDemo.Droid.MainActivity.OnCreate (Android.OS.Bundle savedInstanceState) [0x00000] in <bdc0728e30d74980ad82869dc2b7bae4>:0 
[AndroidRuntime]   at Android.App.Activity.n_OnCreate_Landroid_os_Bundle_ (System.IntPtr jnienv, System.IntPtr native__this, System.IntPtr native_savedInstanceState) [0x0000f] in <1410c4afb1fd4823a12ecf897dd92287>:0 
[AndroidRuntime]   at (wrapper dynamic-method) Android.Runtime.DynamicMethodNameCounter.3(intptr,intptr,intptr)
[AndroidRuntime]    at crc648c69828764ca3d7c.MainActivity.n_onCreate(Native Method)
[AndroidRuntime]    at crc648c69828764ca3d7c.MainActivity.onCreate(MainActivity.java:43)
[AndroidRuntime]    at android.app.Activity.performCreate(Activity.java:8000)
[AndroidRuntime]    at android.app.Activity.performCreate(Activity.java:7984)
[AndroidRuntime]    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1309)
[AndroidRuntime]    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3404)
[AndroidRuntime]    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3595)
[AndroidRuntime]    at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:85)
[AndroidRuntime]    at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
[AndroidRuntime]    at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
[AndroidRuntime]    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2066)
[AndroidRuntime]    at android.os.Handler.dispatchMessage(Handler.java:106)
[AndroidRuntime]    at android.os.Looper.loop(Looper.java:223)
[AndroidRuntime]    at android.app.ActivityThread.main(ActivityThread.java:7660)
[AndroidRuntime]    at java.lang.reflect.Method.invoke(Native Method)
[AndroidRuntime]    at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:592)
[AndroidRuntime]    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:947)

---

這是我的MainActivity.OnCreate() ，在異常消息中提到：

[Activity(ResizeableActivity = true, Label = “My App”, Icon = "@drawable/ic_launcher", MainLauncher = false, ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation, Theme = "@style/MyTheme", LaunchMode = LaunchMode.SingleTop)]
public class MainActivity : Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
    protected override void OnCreate(Bundle savedInstanceState)
    {
        base.OnCreate(savedInstanceState);

        ToolbarResource = Resource.Layout.toolbar;
        TabLayoutResource = Resource.Layout.tabs;
        
        ...
    }
}

這是我的工具欄（在Resources>layout>toolbar.axml下）：

<?xml version="1.0" encoding="utf-8"?>
<androidx.appcompat.widget.Toolbar      // <- before replacing: android.support.v7.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="?attr/actionBarSize"
    android:minHeight="?attr/actionBarSize"
    android:background="?attr/colorPrimary"
    android:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light"
    app:layout_scrollFlags="scroll|enterAlways" />

---

我研究了 AndroidX 遷移教程，在不同的論壇上做了很多研究。 我發現有類似問題的人，但對他們來說，從設備上卸載應用程序並刪除 /bin 和 /obj 文件夾會有所幫助。 對我來說，根本沒有解決它。

（順便說一句：我的應用程序的 iOS 版本正在運行，當然）

Answer 1

當我使用 Xamarin 時，我遇到了同樣的問題，對我來說，它有助於更改下面的鏈接屬性

--> Project.android -> 屬性 -> Anroid 選項 -> 鏈接

切換到無，嘗試啟動您的項目，然后切換回 sdk 和用戶程序集

這個是為我做的

Answer 2

解決方案：刪除toolbar.axml 將修復此錯誤。