MainActivity代码：
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
TextView button = (TextView) findViewById(R.id.change_img_button);
int array[] = { R.drawable.img1, R.drawable.img2, R.drawable.img3, R.drawable.img4,
R.drawable.img5, R.drawable.img6, R.drawable.img7, R.drawable.img8,
R.drawable.img9, R.drawable.img10, R.drawable.img11, R.drawable.img12 };
Random rnd = new Random();
int index = rnd.nextInt(11);
Resources resources = getBaseContext().getResources();
Drawable cur = resources.getDrawable(array[index]);
button.setBackgroundDrawable(cur);
}
}
XML
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<TextView
android:id="@+id/change_img_button"
android:layout_width="match_parent"
android:layout_height="100dp" />
</LinearLayout>
