Landroid/support/v4/animation/AnimatorCompatHelper

java.lang.NoClassDefFoundError: Failed resolution of: Landroid/support/v4/animation/AnimatorCompatHelper;
    at android.support.v7.widget.DefaultItemAnimator.resetAnimation(DefaultItemAnimator.java:515)at android.support.v7.widget.DefaultItemAnimator.animateMove(DefaultItemAnimator.java:255
 
)
    at android.support.v7.widget.DefaultItemAnimator.animateChange(DefaultItemAnimator.java:317)
    at android.support.v7.widget.SimpleItemAnimator.animateChange(SimpleItemAnimator.java:149)
    at android.support.v7.widget.RecyclerView.animateChange(RecyclerView.java:3836)
    at android.support.v7.widget.RecyclerView.dispatchLayoutStep3(RecyclerView.java:3643
 
)
    at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3323)
    at android.support.v7.widget.RecyclerView.consumePendingUpdateOperatio(RecyclerView.java:1637)at android.support.v7.widget.RecyclerView$1.run(RecyclerView.java:343)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:804
 
)
    at android.view.Choreographer.doCallbacks(Choreographer.java:607)
    at android.view.Choreographer.doFrame(Choreographer.java:575)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:790)
    at android.os.Handler.handleCallback(Handler.java:815)
    at android.os.Handler.dispatchMessage(Handler.java:104)
    at android.os.Looper.loop(Looper.java:224)
    at android.app.ActivityThread.main(ActivityThread.java:5929)
    at java.lang.reflect.Method.invoke(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:372)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1113)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:879)
Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.v4.animation.AnimatorCompatHelper" on path: DexPathList[[zip file "/data/app/com.shtoone.smarthelmet-1/base.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_dependencies_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_0_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_1_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_2_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_3_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_4_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_5_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_6_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_7_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_8_apk.apk", zip file "/data/app/com.shtoone.smarthelmet-1/split_lib_slice_9_apk.apk"],nativeLibraryDirectories=[/data/app/com.shtoone.smarthelmet-1/lib/arm64, /vendor/lib64, /system/lib64]]
    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:511)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:469)
    at android.support.v7.widget.DefaultItemAnimator.resetAnimation(DefaultItemAnimator.java:515) 
    at android.support.v7.widget.DefaultItemAnimator.animateMove(DefaultItemAnimator.java:255) 
    at android.support.v7.widget.DefaultItemAnimator.animateChange(DefaultItemAnimator.java:317) 
    at android.support.v7.widget.SimpleItemAnimator.animateChange(SimpleItemAnimator.java:149) 
    at android.support.v7.widget.RecyclerView.animateChange(RecyclerView.java:3836) 
    at android.support.v7.widget.RecyclerView.dispatchLayoutStep3(RecyclerView.java:3643) 
    at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3323) 
    at android.support.v7.widget.RecyclerView.consumePendingUpdateOperations(RecyclerView.java:1637) 
    at android.support.v7.widget.RecyclerView$1.run(RecyclerView.java:343) 
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:804) 
    at android.view.Choreographer.doCallbacks(Choreographer.java:607) 
    at android.view.Choreographer.doFrame(Choreographer.java:575) 
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:790) 
    at android.os.Handler.handleCallback(Handler.java:815) 
    at android.os.Handler.dispatchMessage(Handler.java:104) 
    at android.os.Looper.loop(Looper.java:224) 
    at android.app.ActivityThread.main(ActivityThread.java:5929) 
    at java.lang.reflect.Method.invoke(Native Method) 
    at java.lang.reflect.Method.invoke(Method.java:372) 
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1113) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:879) 
Suppressed: java.lang.ClassNotFoundException:
    android.support.v4.animation.AnimatorCompatHelper
    at java.lang.Class.classForName(Native Method)
    at java.lang.BootClassLoader.findClass(ClassLoader.java:781)
    at java.lang.BootClassLoader.loadClass(ClassLoader.java:841)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:504)
    ... 22 more
Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack available
01-31 08:08:39.897 375-5748/? E/NuPlayer: onScanSources

　　根據CauseBy可知，異常的原因是找不到類導致的。根據查到的資料分析：專案中存在多個support libraries Gradle編譯的時候回優先採用最新版本，而不是你希望採用的版本（翻譯的很勉強，英語不錯的同學可以直接點選參考資料中的連結檢視原文）。
　　我的理解是：我的專案中可能存在多個V4包，而編譯的時候不知道用哪個。乾脆就都不用，所以就出現了找不到類的異常。這是很正常的現象，在引用第三方庫時。三方庫會自帶v4包（用到v4包中的一些函式），三方庫並不能確定其應用環境一定存在v4包。

　　解決方案：在gradle檔案中新增下方程式碼，強制指定版本。

configurations.all {
    resolutionStrategy.eachDependency { DependencyResolveDetails details ->
        def requested = details.requested
        if (requested.group == 'com.android.support') {
            if (!requested.name.startsWith("multidex")) {
                details.useVersion '25.3.0'
            }
        }
    }
}

參考資料