How can I generate a random number in a certain range?

问题

How can I create an app that generates a random number in Android using Eclipse and then show the result in a TextView field? The random number has to be in a range selected by the user. So, the user will input the max and min of the range, and then I will output the answer.

回答1:

To extend what Rahul Gupta said:

You can use the Java function int random = Random.nextInt(n).
This returns a random int in the range [0, n-1].

I.e., to get the range [20, 80] use:

final int random = new Random().nextInt(61) + 20; // [0, 60] + 20 => [20, 80]

To generalize more:

final int min = 20;
final int max = 80;
final int random = new Random().nextInt((max - min) + 1) + min;

回答2:

Random r = new Random();
int i1 = r.nextInt(45 - 28) + 28;

This gives a random integer between 28 (inclusive) and 45 (exclusive), one of 28,29,...,43,44.

回答3:

Also, from API level 21 this is possible:

int random = ThreadLocalRandom.current().nextInt(min, max);

回答4:

" the user is the one who select max no and min no ?" What do you mean by this line ?

You can use java function int random = Random.nextInt(n). This returns a random int in range[0, n-1]).

and you can set it in your textview using the setText() method

回答5:

private int getRandomNumber(int min,int max) {
    return (new Random()).nextInt((max - min) + 1) + min;
}

回答6:

So you would want the following:

int random;
int max;
int min;

...somewhere in your code put the method to get the min and max from the user when they click submit and then use them in the following line of code:

random = Random.nextInt(max-min+1)+min;

This will set random to a random number between the user selected min and max. Then you will do:

TextView.setText(random.toString());

回答7:

You can use If Random. For example, this generates a random number between 75 to 100.

final int random = new Random().nextInt(26) + 75;

回答8:

Random Number Generator in Android If you want to know about random number generator in android then you should read this article till end. Here you can get all information about random number generator in android. Random Number Generator in Android

You should use this code in your java file.

Random r = new Random();
                    int randomNumber = r.nextInt(100);
                    tv.setText(String.valueOf(randomNumber));

I hope this answer may helpful for you. If you want to read more about this article then you should read this article. Random Number Generator

回答9:

Below code will help you to generate random numbers between two numbers in the given range:

private void generateRandomNumbers(int min, int max) {
    // min & max will be changed as per your requirement. In my case, I've taken min = 2 & max = 32

    int randomNumberCount = 10;

    int dif = max - min;
    if (dif < (randomNumberCount * 3)) {
        dif = (randomNumberCount * 3);
    }

    int margin = (int) Math.ceil((float) dif / randomNumberCount);
    List<Integer> randomNumberList = new ArrayList<>();

    Random random = new Random();

    for (int i = 0; i < randomNumberCount; i++) {
        int range = (margin * i) + min; // 2, 5, 8

        int randomNum = random.nextInt(margin);
        if (randomNum == 0) {
            randomNum = 1;
        }

        int number = (randomNum + range);
        randomNumberList.add(number);
    }
    Collections.sort(randomNumberList);
    Log.i("generateRandomNumbers", "RandomNumberList: " + randomNumberList);
}

来源：https://stackoverflow.com/questions/21049747/how-can-i-generate-a-random-number-in-a-certain-range

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