ClassNotFoundException & 应用程序崩溃

Question

我正在使用 Android Studio 开发一个学习应用程序，但是当我运行它时，它会崩溃并给我这个错误代码：

03-29 22:36:03.546 13455-13455/com.training.criminalintent E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.training.criminalintent, PID: 13455
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.training.criminalintent/com.training.criminalintent.CrimeListActivity}: java.lang.ClassNotFoundException: Didn't find class "com.training.criminalintent.CrimeListActivity" on path: DexPathList[[zip file "/data/app/com.training.criminalintent-1/base.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2290)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2442)
    at android.app.ActivityThread.access$800(ActivityThread.java:156)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1351)
    at android.os.Handler.dispatchMessage(Handler.java:102)
    at android.os.Looper.loop(Looper.java:211)
    at android.app.ActivityThread.main(ActivityThread.java:5371)
    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:945)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:740)
Caused by: java.lang.ClassNotFoundException: Didn't find class "com.training.criminalintent.CrimeListActivity" on path: DexPathList[[zip file "/data/app/com.training.criminalintent-1/base.apk"],nativeLibraryDirectories=[/vendor/lib, /system/lib]]
    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.app.Instrumentation.newActivity(Instrumentation.java:1066)
    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2280)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2442) 
    at android.app.ActivityThread.access$800(ActivityThread.java:156) 
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1351) 
    at android.os.Handler.dispatchMessage(Handler.java:102) 
    at android.os.Looper.loop(Looper.java:211) 
    at android.app.ActivityThread.main(ActivityThread.java:5371) 
    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:945) 
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:740) 
Suppressed: java.lang.ClassNotFoundException: com.training.criminalintent.CrimeListActivity
    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)
        ... 13 more
Caused by: java.lang.NoClassDefFoundError: Class not found using the boot class loader; no stack available

我寻找了一个解决方案，但没有找到适合 android studio 的东西，但最重要的是我没有找到问题的根源，为什么 android studio 会这样。

编辑：活动存在于清单文件中：

<application
>     android:allowBackup="true"
>     android:icon="@mipmap/ic_launcher"
>     android:label="@string/app_name"
>     android:supportsRtl="true"
>     android:theme="@style/AppTheme">
>     <activity android:name=".CrimeListActivity">
>         <intent-filter>
>             <action android:name="android.intent.action.MAIN" />
>             <category android:name="android.intent.category.LAUNCHER" />
>         </intent-filter>
>     </activity>
>     <activity android:name=".CrimePagerActivity">
>     </activity> </application>

我还必须明确，在我降级sdk中的tools文件夹之前（与其他软件的兼容性问题）[我将文件夹命名为tools ==> toolsXXXX并下载24.2版本并将tools文件夹放在sdk文件夹中]，它正在工作..

Answer 1

尝试卸载您的应用程序，执行干净的构建，gradle 同步，然后再次运行您的应用程序。

Answer 2

确保com.training.criminalintent.CrimeListActivity 存在于您的AndroidManifest.xml 中。

<activity android:name="com.training.criminalintent.CrimeListActivity" />