Challenge: From Button to ImageButton
Perhaps the UI would look even better if the next and previous buttons showed only icons, as in Figure 2.14.
Figure 2.14 Icon-only buttons
To accomplish this challenge, these two widgets must become ImageButtons instead of regular Buttons.
ImageButton is a widget that inherits from ImageView. Button, on the other hand, inherits from TextView. Figure 2.15 shows their different inheritance hierarchies.
Figure 2.15 Inheritance diagram for