imagebutton的随机图像，无重复（图片拼图）

Question

I have 25 Image Buttons and 1 Shuffle button. when i click the shuffle button, the buttons will display pictures RANDOMLY WITHOUT REPETITION. My problem is that it is having an error whenever i click the shuffle button. It says, "Unfortunately, 'App_Name' has stopped." Help me please. :(

Shuffle.setOnClickListener(new OnClickListener() {
        public void onClick(View v) {
            final int[] easy1 = {R.drawable.a11,R.drawable.a12,R.drawable.a13,R.drawable.a14,R.drawable.a15
                    ,R.drawable.a16,R.drawable.a17,R.drawable.a18,R.drawable.a19,R.drawable.a110
                    ,R.drawable.a111,R.drawable.a112,R.drawable.a113,R.drawable.a114,R.drawable.a115
                    ,R.drawable.a116,R.drawable.a117,R.drawable.a118,R.drawable.a119,R.drawable.a120
                    ,R.drawable.a121,R.drawable.a122,R.drawable.a123,R.drawable.a124};
            int[] a = new int[25];
            int i = 0;
            int j = 0;
            boolean flag = false;

            flag = false;
            i = 1;
            a[j] = 1;

            while (i <= 24){
             rnd = (int)((Math.random() * 24)+1);

             for (j = 1; j <= i; j++){
                    if (a[j] == rnd)
                {
                    flag = true;

                }
            }

             if (flag == true)
                {
                    flag = false;
                }
                else
                {
                    a[i] = rnd;
                    i = i + 1;
                }
            }

    iv1.setImageResource(easy1[a[1]]);
    iv2.setImageResource(easy1[a[2]]);
    iv3.setImageResource(easy1[a[3]]);
    iv4.setImageResource(easy1[a[4]]);
    iv5.setImageResource(easy1[a[5]]);
    iv6.setImageResource(easy1[a[6]]);
    iv7.setImageResource(easy1[a[7]]);
    iv8.setImageResource(easy1[a[8]]);
    iv9.setImageResource(easy1[a[9]]);
    iv10.setImageResource(easy1[a[10]]);
    iv11.setImageResource(easy1[a[11]]);
    iv12.setImageResource(easy1[a[12]]);
    iv13.setImageResource(easy1[a[13]]);
    iv14.setImageResource(easy1[a[14]]);
    iv15.setImageResource(easy1[a[15]]);
    iv16.setImageResource(easy1[a[16]]);
    iv17.setImageResource(easy1[a[17]]);
    iv18.setImageResource(easy1[a[18]]);
    iv19.setImageResource(easy1[a[19]]);
    iv20.setImageResource(easy1[a[20]]);
    iv21.setImageResource(easy1[a[21]]);
    iv22.setImageResource(easy1[a[22]]);
    iv23.setImageResource(easy1[a[23]]);
    iv24.setImageResource(easy1[a[24]]);
    iv25.setImageResource(R.drawable.a3);
        }

    });

Logcat:

01-23 09:08:44.004: E/AndroidRuntime(981): FATAL EXCEPTION: main

01-23 09:08:44.004: E/AndroidRuntime(981): java.lang.ArrayIndexOutOfBoundsException: length=24; index=24

01-23 09:08:44.004: E/AndroidRuntime(981): at com.jepoy.Shift.Main$1.onClick(Main.java:102)

01-23 09:08:44.004: E/AndroidRuntime(981): at android.view.View.performClick(View.java:4084)

01-23 09:08:44.004: E/AndroidRuntime(981): at android.view.View$PerformClick.run(View.java:16966)

01-23 09:08:44.004: E/AndroidRuntime(981): at android.os.Handler.handleCallback(Handler.java:615)

01-23 09:08:44.004: E/AndroidRuntime(981): at android.os.Handler.dispatchMessage(Handler.java:92)

01-23 09:08:44.004: E/AndroidRuntime(981): at android.os.Looper.loop(Looper.java:137)

01-23 09:08:44.004: E/AndroidRuntime(981): at android.app.ActivityThread.main(ActivityThread.java:4745)

01-23 09:08:44.004: E/AndroidRuntime(981): at java.lang.reflect.Method.invokeNative(Native Method)

01-23 09:08:44.004: E/AndroidRuntime(981): at java.lang.reflect.Method.invoke(Method.java:511)

01-23 09:08:44.004: E/AndroidRuntime(981): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)

01-23 09:08:44.004: E/AndroidRuntime(981): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)

01-23 09:08:44.004: E/AndroidRuntime(981): at dalvik.system.NativeStart.main(Native Method)

01-23 09:09:42.344: E/Trace(1029): error opening trace file: No such file or directory (2)

Answer 1

Its quite clear from your logcat what the error is :

01-23 09:08:44.004: E/AndroidRuntime(981): java.lang.ArrayIndexOutOfBoundsException: length=24; index=24

If the length of an array is 24, then index should be 0-23. In your case the index is reaching to 24 tehreby causing out of index error.

make sure that your index should not exceed 23 in case you have 24 items.

Or make your array of size 25 : int[] a = new int[25];

Answer 2

Try to use

i = 0

and

while (i < 24){

Answer 3

final int[] easy1 has 24 elements, so it is indexed 0 to 23. If Math.Random() returns a value just below 1, then multiplying by 24 will give a value between 23 and 24. Adding 1 then gives a value between 24 and 25, which is truncuated to 24 by the int cast.

So a line like iv1.setImageResource(easy1[a[1]]); could attempt to access easy1 at index 24, giving you the error.

Incidentally, the code would be clearer and possibly avoid the bug if you create an instance of java.util.Random and use that to generate an integer random number:

Random random = new Random();
//...
rnd = random.nextInt(23) + 1;

rnd will then contain random integers from 1 to 23.