Xamarin AndroidX 迁移：应用程序启动时崩溃System.InvalidCastException：AndroidX.AppCompat.Widget.Toolbar

编程问答 2022-05-12

问题描述

我最近将我的应用更新为 Xamarin Forms 5.0，因此更新为 AndroidX。我升级了所有包，这些包仍然引用了旧的 Android 支持库，并用来自 AndroidX 的等效引用替换了我的代码中所有出现的 Android 支持库引用。

但我的应用程序在启动时一直崩溃，以下异常：

[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)

这是我的 MainActivity.OnCreate()，异常消息中提到：

[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;
        
        ...
    }
}

这是我的工具栏（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 迁移教程，在不同的论坛上做了很多研究。我发现有类似问题的人，但对于他们从设备上卸载应用程序并删除 /bin 和 /obj 文件夹有帮助。对我来说，根本没有什么能解决它。

（顺便说一句：我的应用程序的 iOS 版本正在运行，当然）

解决方法

暂无找到可以解决该程序问题的有效方法，小编努力寻找整理中！

如果你已经找到好的解决方法，欢迎将解决方案带上本链接一起发送给小编。

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android-support-libraryandroidxxamarinxamarinxamarin.androidxamarin.forms