Android Studio專案會經常遇到這個錯誤，然後就各種Clean Project和Rebuild Project有時候有用有時候沒用，摸不著頭腦

錯誤程式碼如下：

12-18 17:46:01.512 4978-4978/app.dawnling.app E/AndroidRuntime: FATAL EXCEPTION: main
                                                                Process: app.dawnling.app, PID: 4978
                                                                java.lang.RuntimeException: Unable to
 
 instantiate application app.dawnling.app.app.MyApplication: java.lang.ClassNotFoundException: Didn't find class "app.dawnling.app.app.MyApplication" on path: DexPathList[[zip file "/data/app/app.dawnling.app-2/base.apk"],nativeLibraryDirectories=[/data/app/app.dawnling.app-2/lib/x86, /system/lib, /vendor/lib]]
                                                                    at
 
 android.app.LoadedApk.makeApplication(LoadedApk.java:802)
                                                                    at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5377)
                                                                    at android.app.ActivityThread.-wrap2(ActivityThread.java)
                                                                    at
 
 android.app.ActivityThread$H.handleMessage(ActivityThread.java:1545)
                                                                    at android.os.Handler.dispatchMessage(Handler.java:102)
                                                                    at android.os.Looper.loop(Looper.java:154)
                                                                    at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                    at java.lang.reflect.Method.invoke(Native Method)
                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)
                                                                 Caused by: java.lang.ClassNotFoundException: Didn't find class "app.dawnling.app.app.MyApplication" on path: DexPathList[[zip file "/data/app/app.dawnling.app-2/base.apk"],nativeLibraryDirectories=[/data/app/app.dawnling.app-2/lib/x86, /system/lib, /vendor/lib]]
                                                                    at dalvik.system.BaseDexClassLoader.findClass(BaseDexClassLoader.java:56)
                                                                    at java.lang.ClassLoader.loadClass(ClassLoader.java:380)
                                                                    at java.lang.ClassLoader.loadClass(ClassLoader.java:312)
                                                                    at android.app.Instrumentation.newApplication(Instrumentation.java:992)
                                                                    at android.app.LoadedApk.makeApplication(LoadedApk.java:796)
                                                                    at android.app.ActivityThread.handleBindApplication(ActivityThread.java:5377) 
                                                                    at android.app.ActivityThread.-wrap2(ActivityThread.java) 
                                                                    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1545) 
                                                                    at android.os.Handler.dispatchMessage(Handler.java:102) 
                                                                    at android.os.Looper.loop(Looper.java:154) 
                                                                    at android.app.ActivityThread.main(ActivityThread.java:6119) 
                                                                    at java.lang.reflect.Method.invoke(Native Method) 
                                                                    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                                                                    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 

原因猜測：

之所以 Didn’t find class 找不到相關報錯的類，可能是由於類在編譯打包的過程中，沒有全部一起打包上，漏掉了。

解決方法：

1.先刪除專案結構中的 .gradle 資料夾，然後Build->Rebuild Project->Clean Project->Build APK重新執行安裝，即可正常執行

2.如果失敗，請嘗試再次刪除.gradle 和.idea 檔案，重啟 Android Studio ，然後再嘗試。