Wie kann man Bilder per Random ausgeben

someArrayList.add(R.drawable.kat);
		someArrayList.add(R.drawable.hund);
		someArrayList.add(R.drawable.huhn);
		someArrayList.add(R.drawable.kaninchen);

	}

	public void onClick(View v) {
		AssetManager assetManager = getAssets();

		switch (v.getId()) {
		case R.id.bt_choose:

			int random = (int) (Math.random() * 4);

			for (int i = 0; i <= someArrayList.size(); i++) {

				img.setImageResource(someArrayList.get(random));

				try {
					inputStream = assetManager.open("ThemaEins/bild.png");
				} catch (IOException e) {
					e.printStackTrace();
				}

				Drawable d = Drawable.createFromStream(inputStream, null);
				img.setImageDrawable(d);