Create a variable name from a String?

Question

I'm making an Android application and it's got a lot of images (about 200). And I want to show the specific image according to what the user selects.

The selections are in the form of Strings such as "USD", "AUD", "LKR", etc. And the images are in the form "usd.png", "aud.png", "lkr.png" and so on. I have put the images in the /res/drawable-mdpi folder and I usually access them like R.drawable.usd and so on.

But in this case its [obviously] hard to do that (for 200+ icons). So is there anyway I can obtain the specific image according to user selection? For example, when user selects "USD", I want to obtain the image named "usd.png". Any help?

Thanks in advance.

phtrivier · Accepted Answer · 2012-02-23 16:55:52Z

2

Could you use a combination of Resources.getIdentifier and Resources.getDrawable ?

http://developer.android.com/reference/android/content/res/Resources.html#getIdentifier(java.lang.String, java.lang.String, java.lang.String)

http://developer.android.com/reference/android/content/res/Resources.html#getDrawable(int)

answered Feb 23, 2012 at 16:55

phtrivier

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1 Comment

Roshnal Over a year ago

Thanks a lot for your answer! I'll do it this way.. I wasn't aware there was a getIdentifier() method.. :)

Philip Sheard · Accepted Answer · 2012-02-23 17:24:56Z

2

If you can construct the name of the resource, you can call getResources().getIdentifier() to get the id, then you can take it from there.

edited Feb 23, 2012 at 17:24

answered Feb 23, 2012 at 16:55

Philip Sheard

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3 Comments

Roshnal Over a year ago

On what should I call getIdentifier?

Philip Sheard Over a year ago

Sorry, I should have said getResources().getIdentifier().

Roshnal Over a year ago

Thanks for the answer! I'll do it this way, but I'm choosing the other answer (that said the same thing) only because it has some links. Nevertheless, thanks for your answer! +1

Óscar López · Accepted Answer · 2012-02-23 16:50:17Z

0

Use a Map for storing the String as a key, with the image name as a value. For example:

Map<String, String> images = new HashMap<String, String>();
images.put("USD", "usd.png");        // store the reference
String usdImage = images.get("USD"); // retrieve the reference

answered Feb 23, 2012 at 16:50

Óscar López

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5 Comments

Roshnal Over a year ago

Tried that, but I have to store 200+ values like that :) So I was looking for more easier and efficient way of doing it..

Óscar López Over a year ago

200 values is nothing, really! you'll be fine using a Map for that.

Roshnal Over a year ago

I'll look at reflection as the other answerer said, and if its not working as expected, I'll resort to this.. Thanks for the answer!

Óscar López Over a year ago

Refelection can be a very expensive option in terms of performance. Don't reinvent the wheel, what you're asking for is the textbook example of when to use a Map data structure

Roshnal Over a year ago

Some other answerers said to use the Resources.getIdentifier() method in the Android SDK.. If that works, then that's the best method as its a whole lot more efficient and performance-friendly than doing this manually. Another thing, if I add more images and Strings in the future, I wouldn't have to remember to add all of them to the Map :)

Tim Büthe · Accepted Answer · 2012-02-23 16:52:55Z

0

I'm not sure if Android has methods to access the resources by name, however you can always use reflection to do such things in Java:

R.drawable.getClass().getField("nameGoesHere").get(null)

answered Feb 23, 2012 at 16:52

Tim Büthe

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1 Comment

Philip Sheard Over a year ago

Sorry, I should have said getResources().getIdentifier(). I have edited my answer.

Nicolas Zozol · Accepted Answer · 2012-02-23 16:53:09Z

0

The Reflection API is working on Android. It's something that all Java Developer should learn.

answered Feb 23, 2012 at 16:53

Nicolas Zozol

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2 Comments

James Goodwin Over a year ago

Fairly general answer, how exactly would you do that? There's better ways of getting resources by using the Android SDK

Nicolas Zozol Over a year ago

It was my intention to not write a complete answer, to point the utility of the full API, and not just give a quick answer. Learn fishing instead of giving a fish...

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