CODEWITHSUNDEEP
android
Olgun Kaya
Olgun Kaya

Reputation: 2579

Android - Getting a list of drawable resource

In android you can access a resource with syntax like R..

what I want to do is to reach a set of images has naming convention.

for example I have 4 files in drawable with the names :

draw_1_.jpg

how can I get the list of drawable images to List ..

This is because, I want to make a slide show.

thx

Upvotes: 4

Views: 14875

Answers (4)

fdermishin
fdermishin

Reputation: 3686

Although it is an old question, I just had a similar problem recently. I liked solution of jeffd, but storing a list of images ids in code is not the best idea. So, I created an xml file with the list, which I put in res/xml directory.

<?xml version="1.0" encoding="utf-8"?>
<list>
    <image id="@drawable/draw_1"/>
    <image id="@drawable/draw_2"/>
    <image id="@drawable/draw_3"/>
    <image id="@drawable/draw_4"/>
</list>

Images are stored in drawable directory and are named draw_1.jpg, draw_2.jpg, etc.

Using this sort of xml has an advantage that availability of resources is checked at compile time, so if you have a typo, it won't compile.

Retrieving the list in code is simply parsing the xml, yet it's a bit verbose. XmlPullParser has method getAttributeResourceValue that allows getting resource id without dealing with any strings.

List<Integer> list = new ArrayList<>();
try {
    while (parser.next() != XmlPullParser.END_DOCUMENT) {
        if (parser.getEventType() == XmlPullParser.START_TAG &&
            parser.getName().equals("image")) {

            int imageId = -1;
            for (int i = 0; i < parser.getAttributeCount(); ++i) {
                if (parser.getAttributeName(i).equals("id")) {
                    list.add(parser.getAttributeResourceValue(i, -1));
                }
            }
        }
    }
}
catch (XmlPullParserException | IOException e) {
    e.printStackTrace();
}

Another simpler solution would be using arrays as resources. I haven't tried this out, but you can see an example here: http://www.geeks.gallery/how-to-list-images-from-array-xml-in-android/ This is how to structure your xml:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <array name="list">
        <item>@drawable/draw_1</item>
        <item>@drawable/draw_2</item>
        <item>@drawable/draw_3</item>
    </array>
</resources>

To access the array you can use this code:

TypedArray list = getResources().obtainTypedArray(R.array.list);
for (int i = 0; i < list.length(); ++i) {
    int id = list.getResourceId(i, -1);
}

Upvotes: 4

jeffd
jeffd

Reputation: 71

I don't believe you can trust the resource compiler to give your images sequential integer values. In the past I've always created a static array to store these.

private static int[] imgs = { R.id.draw_1, R.id.draw_2, R.id.draw_3, R.id.draw_4 };

With this you can then have a section of code like:

int curSlide = 0;
view.setBackgroundResource(imgs[curSlide]);

Upvotes: 7

Michael George
Michael George

Reputation: 1

You Should identify all the Image as a Drawable .. and then you can use them as you can !

Upvotes: 0

MrJre
MrJre

Reputation: 7161

well, if you know the suffix of the images, you can request the identifier for a drawable by getResources().getIdentifier(...) and then using the identifier get the drawable. So if you know how many images you have, then you can create a loop and store each of the drawables in a list. Just take into account that such a lookup is relatively expensive.

Upvotes: 2

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