Android ClassNotFoundException: Didn't find class on path

I have solved this problem by disabling the instant run option of android studio. To disable Instant Run Goto File -> Settings -> Build,Execution, Deployment -> Instant Run -> Uncheck the checkbox for instant run

I don't know for sure what is your package name, but if it is e.gochat do this.

Add package="e.gochat" to manifest.xml

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="e.gochat"
    .....
    .....
         >

On each activity declaration for android:name put a dot before activity name:

<activity
    android:name=".MainActivity">
............
</activity>

<activity 
    android:name=".ChatActivity">

EDIT

After your edited I can see e.gochat is your package name.
Now you only need to remove e.gochat from each activity/provider/receiver name as I said in second part of my answer.
Android will add that for you.

Using Android Studio

After upgrading to Android Stuido 0.8.2, I had this problem. I tried a lot of things, including

• Clean project
• Clean project (gradle clean)
• Invalidate Caches and Restart
• De-qualify the Activity Name in AndroidManifest.xml (.MyActivity)

Nothing worked until I re-imported the entire project.

File -> Close Project -> Import Project... -> Choose the same project -> OK

This fixed it for me