Caused by: java.lang.ClassNotFoundException: Didn't find class "io.grpc.helloworldexample.Helloworld

FAQ:  Android app 編譯好後安裝到手機，運行時閃退，報以下錯誤：

java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{io.grpc.helloworldexample/io.grpc.helloworldexample.HelloworldActivity}: java.lang.ClassNotFoundException: Didn't find class "io.grpc.helloworldexample.HelloworldActivity" on path: DexPathList[[zip file "/data/app/io.grpc.helloworldexample-aHJfGmXKi-KoAnqDIRZHhQ==/base.apk"],nativeLibraryDirectories=[/data/app/io.grpc.helloworldexample-aHJfGmXKi-KoAnqDIRZHhQ==/lib/arm64, /system/lib64, /vendor/lib64]]

問題緣由：

重複拷貝工程，而且重名工程都在as中打開過，致使as產生混淆，找不到相應類：

 

解決辦法：

直接禁用Instant run, 這個效果最直接

disable Instant Run Go to File -> Settings -> Build,Execution, Deployment -> Instant Run -> Uncheck the checkbox for instant run. Run your app once and this apk file work properly..

試了下下面其餘的辦法，對GRPC上的這個問題解決沒有效果，只能禁用即時編譯，看來這個即時編譯就是一個擺設，不實用，毛病問題太多！！！ 

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其餘的解決辦法（供參考）：

DELETE THAT FOLDER .gradle.

deleted "build" folder under "app" folder.

Change the application name in AndroidManifest to full path
Clean Project
Rebuild Project
Build APK

My problem solved using use multi dex:

android {
defaultConfig {

// Enabling multidex support.
multiDexEnabled true
}
...
}
dependencies
{
compile 'com.android.support:multidex:1.0.0'
}

// in AndroidManifest.xml:
<application
android:name="android.support.multidex.MultiDexApplication" >
...
</application>

public class MyApplication extends MultiDexApplication

Make sure this Diable preDexLibraries

In your app module .gradle file

android {
dexOptions {
  preDexLibraries false
 }

}