ImageButton in an HorizontalSrollView have a frame

I have this Layout:

<HorizontalScrollView android:id="@+id/card_images_horizontalscroll"
   android:layout_height="wrap_content"
   android:layout_width="wrap_content"
   android:scrollbars="none"
   android:visibility="invisible"
   >


    <LinearLayout android:id="@+id/card_images_layout"
        android:orientation="horizontal"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
    >

     <ImageButton 
      android:id="@+id/card_image"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content" 
      android:background="@drawable/icona"
      android:
     />


    </LinearLayout>




  </HorizontalScrollView>

But I meet this issues: the image are enclose by a frame which I don't want, what's wrong?!

Like this:

Thanks so much!

I tried to change XML with this runtime code but I have the same issues:

b = new ImageButton(this);
      开发者_运维知识库      b.setLayoutParams(new LinearLayout.LayoutParams(LinearLayout.LayoutParams.WRAP_CONTENT,LinearLayout.LayoutParams.WRAP_CONTENT));
            b.startAnimation(alpha_animation);
            b.setImageBitmap(myBitmap);

I tried also to follow the suggestion for change ImageButton in Button, but can I set at runtime the image source?

You can add the image to the ImageButton with:

android:src="@drawable/icona"

and then set the background to null like this:

android:background="@null"

Replace your ImageButton with a Button with the background you want:

<Button 
  android:id="@+id/card_image"
  android:layout_width="wrap_content"
  android:layout_height="wrap_content" 
  android:background="@drawable/icona"/>