How to randomly select buttons in android?

Question

I wanted to know how to randomly select a button in android. Like for example there got 4 button, I want the application to randomly choose a button from them and do some actions to it. Here is my code:

Button start;
ImageButton btn1, btn2, btn3, btn4, btn5;
Random random = new Random();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_memory);
    start = (Button)findViewById(R.id.button1);
    start.setOnClickListener(this);
    btn1 = (ImageButton)findViewById(R.id.imageButton1);
    btn2 = (ImageButton)findViewById(R.id.imageButton2);
    btn3 = (ImageButton)findViewById(R.id.imageButton3);
    btn4 = (ImageButton)findViewById(R.id.imageButton4);

}

ImageButton[] all= {btn1, btn2, btn3, btn4};

@Override
public void onClick(View v) {
    if (v == start)
    {
        btn5 = all[random.nextInt(all.length)];
        btn5.setBackgroundColor(Color.RED);
    }
}

If I change to this it work perfectly but then it will only be btn1 and not randomly select.

@Override
public void onClick(View v) {
    if (v == start)
    {
        btn5 = btn1;
        btn5.setBackgroundColor(Color.RED);
    }
}

you need the **btn5** to be perform some actions when the **start** button is clicked — Jagadesh Seeram, Jan 02 '14 at 12:50
You can check like `v.getId() == R.id.button1` if you didn't getting error — Pratik Butani, Jan 02 '14 at 12:53
@PratikButani He was not adding the listeners to the **ImageButton** 's — Jagadesh Seeram, Jan 02 '14 at 12:55
@user3153613 Running Solution : http://stackoverflow.com/a/20883712/1318946 — Pratik Butani, Jan 02 '14 at 13:27

score 2 · Answer 1 · answered Jan 02 '14 at 12:55

2

You need to place this line inside your onCreate() method:

all= {btn1, btn2, btn3, btn4};

As it is now:

ImageButton[] all= {btn1, btn2, btn3, btn4};

It runs in the contractor time where all the buttons are null. Than in the onCreate you assign the buttons for new variables, how ever this does not change ImageButton. Alternativly you could wrote:

ImageButton[0] = (ImageButton)findViewById(R.id.imageButton1);
ImageButton[1] = (ImageButton)findViewById(R.id.imageButton2);
ImageButton[2] = (ImageButton)findViewById(R.id.imageButton3);
ImageButton[3] = (ImageButton)findViewById(R.id.imageButton4);

answered Jan 02 '14 at 12:55

Ilya Gazman

31,250
24
137
216

but if I put `all= {btn1, btn2, btn3, btn4};` It got error. I can`t put `ImageButton[] all;` only – user3153613 Jan 02 '14 at 13:11
@user3153613 Copy past weston answer. We are saying the same thing, I just explain why. – Ilya Gazman Jan 02 '14 at 13:13

score 2 · Accepted Answer · answered Jan 02 '14 at 12:56

all must be set after you have set btn1 etc: Otherwise it'll be an array of nulls.

    btn1 = (ImageButton)findViewById(R.id.imageButton1);
    btn2 = (ImageButton)findViewById(R.id.imageButton2);
    btn3 = (ImageButton)findViewById(R.id.imageButton3);
    btn4 = (ImageButton)findViewById(R.id.imageButton4);
    all= {btn1, btn2, btn3, btn4}; //here
}

ImageButton[] all; //not here

score 0 · Answer 3 · edited May 23 '17 at 10:32

0

How do I generate random integers within a specific range in Java?

check the above reference for generating random number then use

switch(number)
{
case 1:
button.performClick()

.....
}

edited May 23 '17 at 10:32

Community

1
1

answered Jan 02 '14 at 12:51

CoolMonster

2,258
25
50

score 0 · Answer 4 · answered Jan 02 '14 at 12:57

0

do this way

 ImageButton[] all= {btn1, btn2, btn3, btn4};

 Random rand = new Random();
 ImageButton randomBtn = all[rand.nextInt(all.length)];

answered Jan 02 '14 at 12:57

Dhaval Parmar

18,812
8
82
177

score 0 · Answer 5 · answered Jan 02 '14 at 13:08

There is following code which i have run currently:

    Button start;
    ImageButton btn1, btn2, btn3, btn4, btn5;
    Random random;

    int[] all;

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

        random = new Random();

        start = (Button)findViewById(R.id.button1);

        start.setOnClickListener(this);

        btn1 = (ImageButton)findViewById(R.id.ImageButton01);
        btn2 = (ImageButton)findViewById(R.id.ImageButton02);
        btn3 = (ImageButton)findViewById(R.id.ImageButton03);
        btn4 = (ImageButton)findViewById(R.id.ImageButton04);

        all = new int[]{R.id.ImageButton01,R.id.ImageButton02,R.id.ImageButton03,R.id.ImageButton04};
    }



    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.button1)
        {
            int id = all[random.nextInt(all.length)];
            findViewById(id).setBackgroundColor(Color.BLACK);
        }
    }

How to randomly select buttons in android?

5 Answers5