Develop Reference

use shuffelArray as global variable

We are trying to use this array of integers in other methods. Setting the final shuffled Array to a global variable has become next to impossible. We have set other variable as global. The goal here is to have a new int [] fix array every time a button is clicked. We have been able to generate a random int [] ar but can not utilize the array in other methods. So our questions after making the random int [] ar how can we use it in the onClickBtnOne method? Code with comments below
public class MainActivity extends AppCompatActivity {
Button btn1,btn2,btn3,btn4,btn5,btn6;
String T1,T2,T3,T4,T5,T6;
int test[] = new int[7];
int count = 0;
int v1,v2,v3,v4,v5,v6;
int[] fix = {3,2,1,4,6,5};
// Trying to not use above values
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn1 = findViewById(R.id.btn1);
btn2 = findViewById(R.id.btn2);
btn3 = findViewById(R.id.btn3);
btn4 = findViewById(R.id.btn4);
btn5 = findViewById(R.id.btn5);
btn6 = findViewById(R.id.btn6);
main(null);
}
// end onCeate
public static void main(String args[]) {
int [] fix = {1,2,3,4,5,6};
shuffleArray(fix);
// Want to USE this fix shuffleArray
//==================================
for (int i = 0; i < fix.length; i++) {
System.out.print(fix[i] + ",");
}
System.out.println();
}
// Implementing Fisher–Yates shuffle
static void shuffleArray(int [] ar) {
// If running on Java 6 or older, use `new Random()` on RHS here
Random rnd = ThreadLocalRandom.current();
for (int i = ar.length - 1; i > 0; i--) {
int index = rnd.nextInt(i + 1);
// Simple swap
int a = ar[index];
ar[index] = ar[i];
ar[i] = a;
}
}
public void onClickBtnOne(View view){
btn1.setBackgroundColor(getColor(R.color.color_Red));
btn1.setEnabled(false);
count = count + 1;
v1 = count;
test[v1] = count;
if(fix[0] == test[v1]){
// Need a global fix[] here
// =========================
T1 = "true";
if(T1.matches("true")){
btn1.setBackgroundColor(getColor(R.color.color_Yellow));
}
}else {
T1 = "false";
}
}

The array you are trying to use does not have an add method you need to put the values in from another variable like this ar[i] = a; So if you use this type of Array declaration List value = new ArrayList<>(); where you declared the other global variable life will be much easier. Modified code below
This will do the shuffle NOTICE value.clear() without this the List will grow each time it is initialized
public void shf(View view){
value.clear();
for (int i = 1; i <= 6; i++) {
value.add(i);
}
Collections.shuffle(value);
}
And here is your test method call value.get(index) Arrays are ZERO based
public void on1(View view){
btn1.setBackgroundColor(getColor(R.color.color_Red));
btn1.setEnabled(false);
if(value.get(0) == 1){
T1 = "true";
if(T1.matches("true")){
btn1.setBackgroundColor(getColor(R.color.color_Yellow));
}
}else {
T1 = "false";
}
}

two array dimensional ArrayIndexOutOfBoundException and NullPointerException

i wrote a code for calculating some weights. they are integer weights.
and i need to save them in every time the button is clicked.
please help me. i cant see why the compiler gives me an error when i try to push the button for the second time. here is my complete code:
public class TrainingActivity extends Activity {
private EditText etIn1, etIn2, etDesired;
private TextView prevInput;
int W[][] = new int[2][];
int X[][] = new int[30][];
int w0=0, w1=0, w2=0, p=1, sum=0, clicks=0;
private Button nxtData;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.training_activity);
View backgroundImage = findViewById(R.id.background);
Drawable background = backgroundImage.getBackground();
background.setAlpha(40);
etIn1= (EditText) findViewById(R.id.etInput1);
etIn2 = (EditText) findViewById(R.id.etInput2);
etDesired = (EditText) findViewById(R.id.etDesired);
prevInput = (TextView) findViewById(R.id.prevInput);
nxtData = (Button) findViewById(R.id.nextData);
nxtData.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
int sum = 0;
++clicks;
int intetIn1 = Integer.parseInt(etIn1.getText().toString());
int intetIn2 = Integer.parseInt(etIn2.getText().toString());
int intetDesired = Integer.parseInt(etDesired.getText().toString());
X[clicks-1] = new int[] {intetIn1, intetIn2, 1};
prevInput.setText("Last Inputs: (" + intetIn1 + ", " + intetIn2 +
", " + intetDesired + ")");
if(clicks == 1) {
if(intetDesired == 1) {
W[0] = new int[] {intetIn1, intetIn2, 1};
W[1] = W[0];
} else if(intetDesired == (-1)){
W[0] = new int[] {-intetIn1, -intetIn2, -1};
W[1] = W[0];
}
} else if(clicks > 1) {
for(int i=0; i<3; i++){
sum = sum + W[clicks-1][i] * X[clicks-1][i];
} if(sum>0 && intetDesired==1) {
W[clicks] = W[clicks-1];
} else if(sum<0 && intetDesired==(-1)) {
W[clicks] = W[clicks-1];
} else if(sum<=0 && intetDesired==1) {
for(int i=0; i<3; i++) {
W[clicks][i] = W[clicks-1][i] + X[clicks-1][i];
}
} else if(sum>=0 && intetDesired==(-1)) {
for(int i=0; i<3; i++) {
W[clicks][i] = W[clicks-1][i] - X[clicks-1][i];
}
}
}
etIn1.setText("");
etIn2.setText("");
etDesired.setText("");
}
});
}}
and here is the exception it throws:
java.lang.ArrayIndexOutOfBoundsException: length=2; index=2
UPDATEEEEEEEE
i fixed the problem with arrayindexoutofboundexception by changing W[2][] to W[20][]. but in some clicks it gives me this error:
java.lang.NullPointerException
and it's not clear in which clicks. sometimes it's in the second click. or some times it's in fourth click. please help.

W[clicks] = W[clicks - 1];
in above line, you have get error because you have only define size of the array
int W[][] = new int[2][];
so it assigned W[0][] and W[1][] only
When click on second time variable clicks value is 2 then compiler gives ArrayIndexOutOfBoundException
EDITED.............................................................
you have got null value because of your bad logic and not proper way to build two dimensional array. Pls use debug tool to find the actual problem to implement logic and use two dimensional array like below example in java or android:
List<List<Integer>> triangle = new ArrayList<List<Integer>>();
List<Integer> row1 = new ArrayList<Integer>(1);
row1.add(2);
triangle.add(row1);
List<Integer> row2 = new ArrayList<Integer>(2);
row2.add(3);row2.add(4);
triangle.add(row2);
triangle.add(Arrays.asList(6,5,7));
triangle.add(Arrays.asList(4,1,8,3));
System.out.println("Size = "+ triangle.size());
for (int i=0; i<triangle.size();i++)
System.out.println(triangle.get(i));

Generate random number without repetition

bt.setOnClickListener(new OnClickListener(){
#Override
public void onClick(View p1)
{
try{
List<Integer> dataList = new ArrayList<Integer>();
int start = 5;
int end = 15;
for (int i = start; i <= end; i++){
dataList.add(i);
}
Collections.shuffle(dataList);
int[] num = new int[dataList.size()];
for (int i = 0; i < dataList.size(); i++) {
num[i] = dataList.get(i);
}
for (int i = 0; i < num.length; i++) {
t.setText(num[i]);
}
}catch (Exception e) {
e.printStackTrace();
}
}});
I want to show my random number on text view but it shown nothing or crash without catch Exception
What should I do?
What and where is my error?

You should be able to use the diamond operator <>. You can only display one String at a time, so first make a String (and you don't need to copy to an array first). Something like,
try {
List<Integer> dataList = new ArrayList<>(); // <-- <Integer> if you can't.
int start = 5;
int end = 15;
for (int i = start; i <= end; i++) {
dataList.add(i);
}
Collections.shuffle(dataList);
t.setText(dataList.toString());
} catch (Exception e) {
e.printStackTrace();
}

How to generate random number with out duplicates using JSON array in android

I am new to android. I am doing quize app.I have one JSON array text file.how to generate random number with out repetation using JSON array in android..please help me
Thank you adv..
this is my sample code
public static JSONArray getQuesList()throws JSONException{
ArrayList<Integer> list = new ArrayList<Integer>(size);
for(i =size - 1; i >= 0; i--) {
//index = rnd.nextInt(list.size());
list.add(i);
}
Random rand = new Random();
while(list.size() > 0) {
index = rand.nextInt(list.size());
Object object = quesList.get(index);
quesList.put(index, quesList.get(i));
quesList.put(i, object);
Log.d("","Selected: "+list.remove(index));
}
return quesList;

Edited
QuestionActivity.java
Global variable
int[] quizarray = null;
Add two functions
private void createQuizIndex() {
int[] array = new int[QuizFunActivity.getQuesList().length()];
quizarray = new int[QuizFunActivity.getQuesList().length()];
for(int i = 0 ; i < QuizFunActivity.getQuesList().length() ; i++){
array[i] = i;
}
Random random = new Random();
int m = 0;
for (int n = array.length ; n > 0; n--){
int r = random.nextInt(n);
quizarray[m++] = array[r];
array[r] = array[n-1];
}
}
private int getIndexNum(int quesIndex2) {
return quizarray[quesIndex2];
}
Change every showQuestion
showQuestion(getIndexNum(quesIndex),review);
Call createQuizIndex() in line 80, and line 194 if "Retake" means another random quiz

How to set random images to ImageView's?

i am using 9 image view's i want set images to imageview randomly , when I click on refresh button, but I tried like this it's working for random allocation of images but it's repeating the same image in two (or) three imageview's at a time. where is the problem in my code..
final int[] imageViews = {
R.id.imgview11, R.id.imgview12, R.id.imgview13,
R.id.imgview21, R.id.imgview22, R.id.imgview23,
R.id.imgview31, R.id.imgview32, R.id.imgview33 };
final int[] images = {
R.drawable.i1, R.drawable.i2, R.drawable.i3,
R.drawable.i4, R.drawable.i5, R.drawable.i6,
R.drawable.i7, R.drawable.i8, R.drawable.empty };
final ImageButton shuffle = (ImageButton) findViewById(R.id.new_puzzle);
shuffle.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Random generator = new Random();
//int n = 9;
//n = generator.nextInt(n);
//Random random = new Random(System.currentTimeMillis());
for(int v : imageViews) {
ImageView iv = (ImageView)findViewById(v);
iv.setImageResource(images[generator.nextInt(images.length - 1)]);
}
}
});
i don't want repeat, one image for one imageview only..

using the post of blessenm ,i wrote a similar code that you need. check if this helps you.
shuffle.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
Random rng = new Random();
List<Integer> generated = new ArrayList<Integer>();
for (int i = 0; i < 9; i++)
{
while(true)
{
Integer next = rng.nextInt(9) ;
if (!generated.contains(next))
{
generated.add(next);
ImageView iv = (ImageView)findViewById(imageViews[i]);
iv.setImageResource(images[next]);
break;
}
}
}
}
});

Maybe not the perfect answer, but I would just shuffle the images list and the set the resulting image to the imageview.
This will avoid having to generate random numbers that will of course create duplicate (If you throw a dice 6 times, you won't have the numbers 1,2,3,4,5,6 in random order, you will get multiple time the same number.)
Please check everything including the 'i' as I am not in front of my computer.
List<int> list = Arrays.asList(images);
// Here we just simply used the shuffle method of Collections class
// to shuffle out defined array.
Collections.shuffle(list);
int i=0;
// Run the code again and again, then you'll see how simple we do shuffling
for (int picture: list) {
ImageView iv = (ImageView)findViewById(imageViews[i]);
iv.setImageResource(picture);
i++;
}
as an alternative, you may also want to shuffle your list with this code:
public class ShuffleArray {
public static void shuffleArray(int[] a) {
int n = a.length;
Random random = new Random();
random.nextInt();
for (int i = 0; i < n; i++) {
int change = i + random.nextInt(n - i);
swap(a, i, change);
}
}
private static void swap(int[] a, int i, int change) {
int helper = a[i];
a[i] = a[change];
a[change] = helper;
}
public static void main(String[] args) {
int[] a = new int[] { 1, 2, 3, 4, 5, 6, 7 };
shuffleArray(a);
for (int i : a) {
System.out.println(i);
}
}
}

You might want to refer to this post. It shows a method to generate random numbers without duplicates
Creating random numbers with no duplicates