arrays in android programming

Question

I am new in android programming. Here is my question

I tried to declare an array before onCreate() method like

int[] userselected;

Note that i want to use this array to store ids of buttons user had pressed. Then i tried to find no. of elements in this array with

int noOfElements = userselected.length;

which game me an error. Then I changed declaration to

int[] userselected = {};

it worked, but when i tried to put an id in this array with code

userselected[1] = R.id.textview1;

it again gave me an error. I also tried declaring array as

int[] userselected = new int[4];

but then, when i tried to find how many elements have already been stored, userselected.length

always gave number 4.

Please tell me, how can i get what i want

use List then. It is dynamic

Aprian
– Aprian

2012-08-30 08:04:38 +00:00
Commented Aug 30, 2012 at 8:04 — Aprian
– Aprian, Commented Aug 30, 2012 at 8:04

iTurki · Accepted Answer · 2012-08-30 08:19:39Z

5

You need to use ArrayList. It will give you a more flexible structure giving your case.

ArrayList<Integer> userselected  = new  ArrayList<Integer>();
userselected.add(R.id.textview1); //To add id.
int noOfElement = userselected.size(); //to get size

edited Aug 30, 2012 at 8:19

answered Aug 30, 2012 at 8:04

iTurki

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6 Comments

Pankaj Kumar Over a year ago

What is problem in this code example? I am asking to downvoters...... first read the rule to do downvote and then proceed. Don't show here your jealous behavior.

Lalit Poptani Over a year ago

is user asking for ArrayList any where? The OP can suggest that you can use ArrayList giving reason why to use it.

Pankaj Kumar Over a year ago

Thats a good reason to downvote, but when you give downvote you should be clear about your thought to OP. Am I right?

iTurki Over a year ago

@LalitPoptani Sorry. Updated with reason. With his requirement, arrays will be difficult to implement. ArrayList is what he should use giving his specific case.

Amit Mittal Over a year ago

yes buddy !! your solution worked. I dont know, why you were downvoted. but all i required was a solution, and you gave that

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twigg · Accepted Answer · 2012-08-30 08:42:38Z

1

an array is fixed size. so when you declare this array

int[] userselected = new int[4]

you are creating an array with a fixed size of 4. The array index is zero based so its from [0] to [3]. I recommend you use an ArrayList object like the top answer states

when you do this:

int[] userselected = {};

it is the same as this:

int[] userselected = new int[0]; // empty

and you got an error from this:

int[] userselected;

because you have not allocated any space in memory

edited Aug 30, 2012 at 8:42

answered Aug 30, 2012 at 8:30

twigg

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Comments

soren.qvist · Accepted Answer · 2012-08-30 08:04:42Z

0

Java primitive arrays, such as int[], are constant in length and cannot contain more than their initial length. If you need an array that can change in size, you need to use fx. a List implementation. I would suggest you read up on basic Java before you start developing Android, it would save you a lot of time in the long run.

answered Aug 30, 2012 at 8:04

soren.qvist

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1 Comment

Amit Mittal Over a year ago

You are right, but learning this way isn't bad either, i think

aelbaz · Accepted Answer · 2012-08-30 08:05:29Z

0

I think this page can help: http://www.javaclass.info/classes/java-array/array-examples-demonstration-and-code-snippets.php

In the array declaration you do, you say that its size is 4 elements, therefore the length method will always return 4.

regards

answered Aug 30, 2012 at 8:05

aelbaz

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Comments

Manoj Kumar · Accepted Answer · 2012-08-30 10:16:37Z

0

declare it as a integer array then Add this to your code

Integer a=0;
for (int i=0;i>userselected.length;i++)
{
   if(userselected[i]!=null)
    {
      a++;
    }
}

then a will give you the count you need:) cheers:)

edited Aug 30, 2012 at 10:16

answered Aug 30, 2012 at 8:06

Manoj Kumar

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1 Comment

Amit Mittal Over a year ago

its giving operator != is not defined for the type int, null. Also your loop is incorrect, which i corrected

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