How can you always arrange picture pairs randomly in another place?

I'm trying to develop a Memory game for Android. I don't know how to arrange picture pairs randomly in another place. I've already managed to arrange one or two pairs of pictures at random ImageViews, but I have the problem that as soon as I want to arrange several pictures pairs, sometimes only single pictures are displayed and some ImageViews show no picture.

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    final ImageView iv[] = {(ImageView) findViewById(R.id.pic1), (ImageView) findViewById(R.id.pic2), (ImageView) findViewById(R.id.pic3), (ImageView) findViewById(R.id.pic4),
            (ImageView) findViewById(R.id.pic5), (ImageView) findViewById(R.id.pic6),
            (ImageView) findViewById(R.id.pic7),
            (ImageView) findViewById(R.id.pic8),
            (ImageView) findViewById(R.id.pic9),
            (ImageView) findViewById(R.id.pic10),
            (ImageView) findViewById(R.id.pic11),
            (ImageView) findViewById(R.id.pic12),
            (ImageView) findViewById(R.id.pic13),
            (ImageView) findViewById(R.id.pic14)};
    Random random = new Random();

    int  picture[] = {R.drawable.i1, R.drawable.i2, R.drawable.i3, R.drawable.i4, R.drawable.i5, R.drawable.i5, R.drawable.i6, R.drawable.i7};

    int i = random.nextInt(13);

    iv[i].setImageResource(picture[1]);

    i = random.nextInt(13);

    iv[i].setImageResource(picture[1]);


    i = random.nextInt(13);

    iv[i].setImageResource(picture[2]);

    i = random.nextInt(13);

    iv[i].setImageResource(picture[2]);


    i = random.nextInt(13);

    iv[i].setImageResource(picture[3]);

    i = random.nextInt(13);

    iv[i].setImageResource(picture[3]);


    i = random.nextInt(13);

    iv[i].setImageResource(picture[4]);

    i = random.nextInt(13);

    iv[i].setImageResource(picture[4]);


    i = random.nextInt(13);

    iv[i].setImageResource(picture[5]);

    i = random.nextInt(13);

    iv[i].setImageResource(picture[5]);


    i = random.nextInt(13);

    iv[i].setImageResource(picture[6]);

    i = random.nextInt(13);

    iv[i].setImageResource(picture[6]);

}

How can I fix that? Is it possible to generate another random number each time?