How do I make an Image Randomizer on Android Stuido?

Hello, I am in an android app design class in my junior year of high school. I am trying to make a Magic 8 Ball app for my final project. I am trying to figure out a way to produce a random image out of my drawable file. I used Photoshop to create the images of 20 triangles with every different saying on them. I am kind of new to this and really have no idea what I am doing. This is what I have so far. Anyone wanna help?

int[] images = new int[]{R.drawable.Magic_8_Ball_Triangle_1,R.drawable.Magic_8_Ball_Triangle_2,R.drawable.Magic_8_Ball_Triangle_3,R.drawable.Magic_8_Ball_Triangle_4,R.drawable.Magic_8_Ball_Triangle_5,R.drawable.Magic_8_Ball_Triangle_6,R.drawable.Magic_8_Ball_Triangle_7,R.drawable.Magic_8_Ball_Triangle_8,R.drawable.Magic_8_Ball_Triangle_9,R.drawable.Magic_8_Ball_Triangle_10,R.drawable.Magic_8_Ball_Triangle_11,R.drawable.Magic_8_Ball_Triangle_12,R.drawable.Magic_8_Ball_Triangle_13,R.drawable.Magic_8_Ball_Triangle_14,R.drawable.Magic_8_Ball_Triangle_15,R.drawable.Magic_8_Ball_Triangle_16,R.drawable.Magic_8_Ball_Triangle_17,R.drawable.Magic_8_Ball_Triangle_18,R.drawable.Magic_8_Ball_Triangle_19,R.drawable.Magic_8_Ball_Triangle_20};