Android, getting resource ID from string?

Question

I need to pass a resource ID to a method in one of my classes. It needs to use both the id that the reference points to and also it needs the string. How should I best achieve this?

For example:

R.drawable.icon

I need to get the integer ID of this, but I also need access to the string "icon".

It would be preferable if all I had to pass to the method is the "icon" string.

is it possible in similar way to getId of files saved to internal storage? I have problem cause I should supply array of ids instead of locations to my gallery (thought it's adapter).. thanks — Ewoks
– Ewoks, Commented Feb 24, 2012 at 10:16
@Ewoks: They don't have IDs on internal storage. They're just images, if anything you need to load them into a bunch of Image objects and pass those, you might want to start a new question though. — Hamid
– Hamid, Commented Feb 27, 2012 at 10:43
possible duplicate of How to get a resource id with a known resource name? — Jannie Theunissen
– Jannie Theunissen, Commented Jun 11, 2015 at 13:17

Volo · Accepted Answer · 2023-07-27 17:12:27Z

@EboMike: I didn't know that Resources.getIdentifier() existed.

In my projects I used the following code to do that:

public static int getResId(String resName, Class<?> c) { try { Field idField = c.getDeclaredField(resName); return idField.getInt(idField); } catch (Exception e) { e.printStackTrace(); return -1; } }

It would be used like this for getting the value of R.drawable.icon resource integer value

int resID = getResId("icon", R.drawable.class); // or other resource class

I just found a blog post saying that Resources.getIdentifier() is slower than using reflection like I did. Check it out.

WARNING: This solution will fail in the release build if code/resource shrinking is enabled as suggested by Google: https://developer.android.com/build/shrink-code
Also, it might fail for some other cases, e.g. when you have <string name="string.name">…</string> the actual field name will be string_name and not the string.name

@Macarse: Presently, getIdentifier() has to do two reflection lookups. In your example above, getIdentifier() would use reflection to get Drawable.class, then another reflection lookup to get the resource ID. That would account for the speed difference. That being said, neither are especially quick and therefore really need to be cached (particularly if used in a loop, or for rows in a ListView). And the reflection approach's big problem is that it makes assumptions about the internals of Android that might change in some future release.
@CommonsWare: That's right. I was checking how android implemented and it ends ups being a native call. gitorious.org/android-eeepc/base/blobs/… => gitorious.org/android-eeepc/base/blobs/…
I would use an integer array with the IDs instead. Using strings for IDs doesn't sound like the right approach.
Calling should be getId("icon", R.drawable.class); not getResId("icon", context, Drawable.class);

marca311 · Accepted Answer · 2013-11-26 16:24:11Z

98

You can use this function to get resource ID.

public static int getResourceId(String pVariableName, String pResourcename, String pPackageName) { try { return getResources().getIdentifier(pVariableName, pResourcename, pPackageName); } catch (Exception e) { e.printStackTrace(); return -1; } }

So if you want to get for drawable call function like this

getResourceId("myIcon", "drawable", getPackageName());

and for string you can call it like this

getResourceId("myAppName", "string", getPackageName());

Read this

edited Nov 26, 2013 at 16:24

marca311

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answered Sep 30, 2013 at 11:48

Azhar

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4 Comments

Ricardo Meneghin Filho Over a year ago

What is the point of making a function that simply calls another one and "handles" a possible exception? Call getResources().getIdentifier() directly.

Shankari Over a year ago

Upvoted for clarifying how to pass in the type to get different kinds or resources. The android dev documentation does not have details and "id" from a prior answer does not work for strings.

android developer Over a year ago

Is there also the opposite? Meaning from R.string.some_string to "some_string" ?

Darksymphony Over a year ago

Use of getIdentifier is discouraged because resource reflection makes it harder to perform build optimizations and compile-time verification of code

Jonik · Accepted Answer · 2015-02-25 15:16:08Z

This is based on @Macarse answer.

Use this to get the resources Id in a more faster and code friendly way.

public static int getId(String resourceName, Class<?> c) { try { Field idField = c.getDeclaredField(resourceName); return idField.getInt(idField); } catch (Exception e) { throw new RuntimeException("No resource ID found for: " + resourceName + " / " + c, e); } }

Example:

getId("icon", R.drawable.class);

OneCricketeer · Accepted Answer · 2016-09-06 17:08:33Z

How to get an application resource id from the resource name is quite a common and well answered question.

How to get a native Android resource id from the resource name is less well answered. Here's my solution to get an Android drawable resource by resource name:

public static Drawable getAndroidDrawable(String pDrawableName){ int resourceId=Resources.getSystem().getIdentifier(pDrawableName, "drawable", "android"); if(resourceId==0){ return null; } else { return Resources.getSystem().getDrawable(resourceId); } }

The method can be modified to access other types of resources.

now .getResources().getDrawable is deprecated if(android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP){ return mContext.getDrawable(resourceId); } else { return mContext.getResources().getDrawable(resourceId); }
also use of getIdentifier is discouraged because resource reflection makes it harder to perform build optimizations and compile-time verification of code

Peter Knego · Accepted Answer · 2011-05-14 21:08:16Z

If you need to pair a string and an int, then how about a Map?

static Map<String, Integer> icons = new HashMap<String, Integer>(); static { icons.add("icon1", R.drawable.icon); icons.add("icon2", R.drawable.othericon); icons.add("someicon", R.drawable.whatever); }

Vasily Kabunov · Accepted Answer · 2023-04-05 07:29:45Z

10

Simple method to get resource ID:

public int getDrawableName(Context ctx, String str){ return ctx.getResources().getIdentifier(str,"drawable", ctx.getPackageName()); }

edited Apr 5, 2023 at 7:29

Vasily Kabunov

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answered Oct 9, 2017 at 11:42

Ivan Vovk

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2 Comments

xMRi Over a year ago

Would be better if you just give some more information to your answer.

Darksymphony Over a year ago

Use of getIdentifier is discouraged because resource reflection makes it harder to perform build optimizations and compile-time verification of code

Sarvar Nishonboyev · Accepted Answer · 2013-07-26 13:49:08Z

9

I did like this, it is working for me:

 imageView.setImageResource(context.getResources(). getIdentifier("drawable/apple", null, context.getPackageName()));

answered Jul 26, 2013 at 13:49

Sarvar Nishonboyev

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2 Comments

kosiara - Bartosz Kosarzycki Over a year ago

Thanks. Works as expected. I used the following: view.context.resources.getIdentifier("drawable/item_car_$position", null, context.packageName).

Darksymphony Over a year ago

Use of getIdentifier is discouraged because resource reflection makes it harder to perform build optimizations and compile-time verification of code

EboMike · Accepted Answer · 2010-12-13 09:58:45Z

8

You can use Resources.getIdentifier(), although you need to use the format for your string as you use it in your XML files, i.e. package:drawable/icon.

answered Dec 13, 2010 at 9:58

EboMike

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1 Comment

Steve Waring Over a year ago

My answer below is the reverse of this. Pass in the resource id, and then use getResourceEntryName(id) to find the string name. No messing to find "icon" from the longer text.

Krešimir Prcela · Accepted Answer · 2021-02-28 16:49:18Z

The Kotlin approach

inline fun <reified T: Class<*>> T.getId(resourceName: String): Int { return try { val idField = getDeclaredField (resourceName) idField.getInt(idField) } catch (e:Exception) { e.printStackTrace() -1 } }

Usage:

val resId = R.drawable::class.java.getId("icon")

Or:

val resId = R.id::class.java.getId("viewId")

This works but what exactly is this doing? It has a very weird syntax. How is it performance wise?

Steve Waring · Accepted Answer · 2014-08-02 07:32:48Z

Since you said you only wanted to pass one parameter and it did not seem to matter which, you could pass the resource identifier in and then find out the string name for it, thus:

String name = getResources().getResourceEntryName(id);

This might be the most efficient way of obtaining both values. You don't have to mess around finding just the "icon" part from a longer string.

Leos Literak · Accepted Answer · 2016-05-16 15:37:38Z

A simple way to getting resource ID from string. Here resourceName is the name of resource ImageView in drawable folder which is included in XML file as well.

int resID = getResources().getIdentifier(resourceName, "id", getPackageName()); ImageView im = (ImageView) findViewById(resID); Context context = im.getContext(); int id = context.getResources().getIdentifier(resourceName, "drawable", context.getPackageName()); im.setImageResource(id);

Gene · Accepted Answer · 2018-04-03 05:25:31Z

In your res/layout/my_image_layout.xml

<LinearLayout ...> <ImageView android:id="@+id/row_0_col_7" ...> </ImageView> </LinearLayout>

To grab that ImageView by its @+id value, inside your java code do this:

String row = "0"; String column= "7"; String tileID = "row_" + (row) + "_col_" + (column); ImageView image = (ImageView) activity.findViewById(activity.getResources() .getIdentifier(tileID, "id", activity.getPackageName())); /*Bottom code changes that ImageView to a different image. "blank" (R.mipmap.blank) is the name of an image I have in my drawable folder. */ image.setImageResource(R.mipmap.blank);

Daniele D. · Accepted Answer · 2016-05-27 17:03:20Z

In MonoDroid / Xamarin.Android you can do:

 var resourceId = Resources.GetIdentifier("icon", "drawable", PackageName);

But since GetIdentifier it's not recommended in Android - you can use Reflection like this:

 var resourceId = (int)typeof(Resource.Drawable).GetField("icon").GetValue(null);

where I suggest to put a try/catch or verify the strings you are passing.

bitvale · Accepted Answer · 2016-06-29 10:50:20Z

For getting Drawable id from String resource name I am using this code:

private int getResId(String resName) { int defId = -1; try { Field f = R.drawable.class.getDeclaredField(resName); Field def = R.drawable.class.getDeclaredField("transparent_flag"); defId = def.getInt(null); return f.getInt(null); } catch (NoSuchFieldException | IllegalAccessException e) { return defId; } }

Evillight · Accepted Answer · 2023-12-22 14:01:30Z

 ImageId.substring(0, ImageId.length()-1); imageMessage = (ImageView) findViewById(R.id.imageMessage); int resID = getResources().getIdentifier(ImageId , "drawable", getPackageName()); imageMessage.setImageResource(resID);

Dont forget to add substring

Asad Khan · Accepted Answer · 2024-08-03 13:08:18Z

 //Inside main class int resID = getId(buttonID); findViewById(resID);

Use the method below

 private int getId (String resourceName) { try { Field idField = R.id.class.getDeclaredField(resourceName); return idField.getInt(idField); } catch (Exception e) { throw new RuntimeException("No resource ID found for: " + resourceName + " / ", e); } }

For ID use R.id.class

For Drawable Use R.Drawable.class

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