How to randomize(or shuffle) order of Radio Buttons

Question

I want to randomize my radio buttons whenever I reopen my app.

For example my layout is like below:

RBtn1
Rbtn2
Rbtn3
Rbtn4

Now I want to shuffle them whenever I open that particular activity. How can I do this?

Answer 1

As far I know, Layouts in resources are immutable. That means you've to make Views in the dynamic or Java way.

What you can do is use the SecureRandom class (accurate than Random for picking random numbers) to pick a random number and take one RadioButton object from the RadioButton array what you will create.

PoC: I'm explaining first by a now written and tested code →

import java.util.*;

public class HelloWorld{

     static String los1 = "taotao1";
     static String los2 = "taotao2";
     static String los3 = "taotao3";
     static String los4 = "taotao4";

     static String[] X = {los1,los2,los3,los4};

     public static void main(String []args){
             Collections.shuffle(Arrays.asList(X));
             System.out.println(Arrays.toString(X));
     }

     /*
     Test 1 : [taotao4, taotao3, taotao2, taotao1]
     Test 2 : [taotao2, taotao3, taotao4, taotao1]
     Test 3 : [taotao3, taotao4, taotao1, taotao2]
     Test 4 : [taotao2, taotao4, taotao1, taotao3]
     */

}

Explanation: Collections.shuffle shuffles objects in an Array as you will be able to see by running code.

Conceptual Code: I'm saying it conceptual because writing directly in Stack Answer Box without testing, Test to be done by you.

public class NoNotHelloWorld extends Activity{

    @Override
    protected void onCreate(Bundle savedInstanceState) {

     RadioButton r1,r2,r3,r4; //please declare to avoid NullPtr and also declare their functionalities 

     LinearLayout xyz = (LinearLayout)findViewById(R.id.xyzwhatisthis);
    //though unnesseary cast, but I did it.

    ArrayList<RadioButton>  dydx = new ArrayList<RadioButton>(); 
        dydx.add(r1); 
        dydx.add(r2); 
        dydx.add(r3); 
        dydx.add(r4); 

    Collections.shuffle(Arrays.asList(arr));

    for(RadioButton dxdy : dydx){
        xyz.addView(dxdy)
    }

    }

}

I think it should work otherwise comment box is there.