Unable to instantiate activity in android

Most times this error has to do with the Manifest.xml file.

My advice is first to check  the Main Activity name if is the same with the Activity you use in your code:
<activity android:name=".MainActivity" />

And then check if your package got the same name as you named it when you create the Project.
You can find "package" property inside :
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="" >


It's a common mistake if you import your project code from another project or you change the main activity name.

Add project to working set - eclipse

right click on the working set you want and then click on Properties.

Select the project and Add it to the Working set content.

Remove Title Bar on Android

Remember when you wrote the first "Hello World" app ?

Hello World or whatever you named it appears in the title bar of Android.

Go to the manifest file. Find the <application> tag and change it to this :


    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@android:style/Theme.NoTitleBar"
         >

we have added the code in bold... it does the work for us. Now just run again your app.

java.lang.IllegalAccessError: Class ref in pre-verified class resolved to unexpected implementation

Well that's a common error if u are messing around with google maps api.

go to Project > Properties > Java Build Path > Libraries and ensure that there is no android.jar or maps.jar directly included. You should only have Google Apis with at leastmaps.jar and android.jar as leaves.

As u can see in the image there are two maps.jar . You have to delete the first one and just leave the leaves of Google APIs

java.io.IOException: Unable to open sync connection

Mess a lot with the code and now the error i get is :

java.io.IOException: Unable to open sync connection!

as u can check @ stackoverflow the answer is to enable/disable the usb-debugging


Some other tips that may can help u is to reboot your device, unplug it from the PC and plug it again.

E/MapActivity(2964): Couldn't get connection factory client

It has something to do with Android Google Maps.

I guess its not the API KEY, since im not having any problems and my app works just fine.

Seems it still is a bug no matter what SDK version you use.

http://code.google.com/p/android/issues/detail?id=8816

Also from Stackoverflow is provided a workaround check the link here