View - Has no zero argument constructor

Question

I'm following the tutorial at https://github.com/codepath/android_guides/wiki/Basic-Painting-with-Views which states that to get started I should create a view:

public class SimpleDrawingView extends View {
    public SimpleDrawingView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
}

Note that up to here everything is fine. I then add the XML layout:

<com.codepath.example.simpledrawapp.SimpleDrawingView
        android:id="@+id/simpleDrawingView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentLeft="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true" />

Now I've tried to do the following on my own code, and even with the exact code provided every time I run the emulator I get the following error:

java.lang.InstantiationException: java.lang.Class<com.company.cw.MainActivity> has no zero argument constructor
    enter code here

Any ideas on how to solve this seemingly trivial issue?

Answer 1

The problem has nothing to do with your view. It has to do with com.company.cw.MainActivity . If you look at your error message, you will see that it does not mention your view, but does mention com.company.cw.MainActivity .

Your question does not include the code for com.company.cw.MainActivity , but apparently it implements a constructor, particularly one that takes parameters. Do not do this . For starters, it will never be invoked, so it's a waste of keystrokes. Whatever initialization you want to do should be in onCreate() , typically after super.onCreate() .