ClassNotFoundException: Didn't find class on path: DexPathList

Update

After a long time, It turned out that it must have anything to do with proguard. I can´t really say what exactly the error causes, but I tried a little bit and that´s what I noticed (that´s in my case with Eclipse IDE):

• I have to close every tab from the project I want to sign
• I have to clean the project and after cleaning, do nothing but export the apk
• making a small change in manifest, save it and undo the change (and save)
• if there is any class in manifest named with "YourClass" or ".YourClass", change it to "com.yourpackage.yourClass"

That are the four points I have done and then it worked. This looks suspicious, but I think there is a problem with obfuscating. Because without doing these points, I can simply compile my apk and install it from eclipse. For me, there is no obvious reason for this behavior.Also the package name does work without a change if I only install it from eclipse. I hope these points can help somebody.

If you manifest package name is ok,If you clossed the project, and within file explorer renamed your project but after importing one you again encounter this problemthe only way here is to

DELETE THAT FOLDER .gradle.

This one can be found in project folder using file explorer.It has artifact files that contain that old project's name.After you reopen the project in Android Studio the folder will be recreated automatically.

I just changed my gradle from com.android.tools.build:gradle:2.2.2 to com.android.tools.build:gradle:2.2.0，and the problem is fine！