Parent does not contain a constructor that takes 0 arguments

问题

My code is

 namespace classlibrary
 {
   public class numerictext : EditText
    {
      //My code

    }

When I try to inherit a edit text control in a class library, I'm getting the error: Parent does not contain a constructor that takes 0 arguments. I understand the problem is that Parent has no constructor with 0 arguments. But how to inherit a control in a class library?

回答1:

You need to call one of the base constructors in your derived class. Assuming you are using the Android EditText widget:

public class numerictext : EditText
{
    public numerictext(Context context) : base(context)
                                      //^^^^^^^^^^^^^^^ 
                                      //Note how we are now calling the base constructure
    {
        //empty or you can add your own code
    }

    public numerictext(Context context, IAttributeSet attrs) : base(context, attrs)
    {
    }

    //etc
}

回答2:

For any Android-based View subclass, you need to supply the three constructors that call their base object constructors, ie.:

public class MyView : EditText
{
    public MyView(Context context) : base(context) { }
    public MyView(Context context, IAttributeSet attrs) : base(context, attrs) { }
    public MyView(Context context, IAttributeSet attrs, int defStyle) : base(context, attrs, defStyle) { }

    // your override code....
}

回答3:

Have you considered changing EditText to:

public class EditTtext 
{
   data stuff..
   EditText() {}

   other functions
}

Though I don't see why yours wouldn't work as is

来源：https://stackoverflow.com/questions/51233923/parent-does-not-contain-a-constructor-that-takes-0-arguments

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android

Xamarin

uwp