Custom global Application class breaks with "android.app.Application cannot be cast to"

I have a custom global class which looks like this

import android.app.Application;

public class MyApp extends Application {

    public String MainAct;

    public String getMainAct() {
        return MainAct;
    }

    public void setMainAct(String mainAct) {
        MainAct = mainAct;
    }
}

I want to preserve a string in this class via another Activity in its onCreate method.

    String local = "myLocalVariable";
    ((MyApp) getApplication()).setMainAct(local); //breaks here!!!
    String name = ((MyApp) getApplication()).getMainAct();

It breaks on the marked line with error: Caused by: java.lang.ClassCastException: android.app.Application cannot be cast to com.xxx.yyy.global.MyApp

I've checked the code for five times and I cannot find error anywhere. Can anyone tell me where the error is?!

Thanks

The error states that the type of the object returned by getApplication is android.app.Application. A possible cause for this is that you failed to define the application in the manifest. Make sure that your manifest includes something in the lines of:

<application android:name=".MyApp"...
</application>

Another solution for older Android devices or emulators. You defined an application in the manifest:

    <application 
           android:name=".MyApp"...
    </application>

but you still have this problem?

Try to disable instant run:

1. Disable an Instant run
2. Clean and rebuild the project
3. Remove the app from device and install it again without Instant run