Java Android Studio Errorr OnCreate

似乎您没有使用RecyclerView所需的依赖项。 在你的应用程序gradle中，你需要为它添加实现

Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.v7.widget.RecyclerView" on path: DexPathList[[zip file "/data/app/com.example.portal-EKCI7lVL-Rh78pQFpEWO_A==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.portal-EKCI7lVL-Rh78pQFpEWO_A==/lib/arm64, /system/lib64]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:134)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at android.view.LayoutInflater.createView(LayoutInflater.java:610)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:794)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:734)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:867)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:828)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:519)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:427)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
        at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:469)
        at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:140)
        at com.example.portal.MainActivity.onCreate(MainActivity.java:34)
        at android.app.Activity.performCreate(Activity.java:7224)
        at android.app.Activity.performCreate(Activity.java:7213)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2926)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3081)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1831)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:201)
        at android.app.ActivityThread.main(ActivityThread.java:6810)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)

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这取决于你的编译版本。如果您添加此行，Android Studio将告诉您此版本的RecyclerView是否与您的应用程序兼容。

似乎您没有使用RecyclerView所需的依赖项。 在你的应用程序gradle中，你需要为它添加实现

Caused by: java.lang.ClassNotFoundException: Didn't find class "android.support.v7.widget.RecyclerView" on path: DexPathList[[zip file "/data/app/com.example.portal-EKCI7lVL-Rh78pQFpEWO_A==/base.apk"],nativeLibraryDirectories=[/data/app/com.example.portal-EKCI7lVL-Rh78pQFpEWO_A==/lib/arm64, /system/lib64]]
        at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:134)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:379)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
        at android.view.LayoutInflater.createView(LayoutInflater.java:610)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:794)
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:734)
        at android.view.LayoutInflater.rInflate(LayoutInflater.java:867)
        at android.view.LayoutInflater.rInflateChildren(LayoutInflater.java:828)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:519)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:427)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:374)
        at androidx.appcompat.app.AppCompatDelegateImpl.setContentView(AppCompatDelegateImpl.java:469)
        at androidx.appcompat.app.AppCompatActivity.setContentView(AppCompatActivity.java:140)
        at com.example.portal.MainActivity.onCreate(MainActivity.java:34)
        at android.app.Activity.performCreate(Activity.java:7224)
        at android.app.Activity.performCreate(Activity.java:7213)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1272)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2926)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3081)
        at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:78)
        at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:108)
        at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:68)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1831)
        at android.os.Handler.dispatchMessage(Handler.java:106)
        at android.os.Looper.loop(Looper.java:201)
        at android.app.ActivityThread.main(ActivityThread.java:6810)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:547)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:873)

这取决于你的编译版本。如果您添加此行，Android Studio将告诉您此版本的RecyclerView是否与您的应用程序兼容