[java] How to get a resource id with a known resource name?

I want to access a resource like a String or a Drawable by its name and not its int id.

Which method would I use for this?

// image from res/drawable
    int resID = getResources().getIdentifier("my_image", 
            "drawable", getPackageName());
// view
    int resID = getResources().getIdentifier("my_resource", 
            "id", getPackageName());

// string
    int resID = getResources().getIdentifier("my_string", 
            "string", getPackageName());

I would suggest you using my method to get a resource ID. It's Much more efficient, than using getIdentidier() method, which is slow.

Here's the code:

/**
 * @author Lonkly
 * @param variableName - name of drawable, e.g R.drawable.<b>image</b>
 * @param ? - class of resource, e.g R.drawable.class or R.raw.class
 * @return integer id of resource
 */
public static int getResId(String variableName, Class<?> ?) {

    Field field = null;
    int resId = 0;
    try {
        field = ?.getField(variableName);
        try {
            resId = field.getInt(null);
        } catch (Exception e) {
            e.printStackTrace();
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    return resId;

}

in addition to @lonkly solution

1. see reflections and field accessibility
2. unnecessary variables

method:

/**
 * lookup a resource id by field name in static R.class 
 * 
 * @author - ceph3us
 * @param variableName - name of drawable, e.g R.drawable.<b>image</b>
 * @param ?            - class of resource, e.g R.drawable.class or R.raw.class
 * @return integer id of resource
 */
public static int getResId(String variableName, Class<?> ?)
                     throws android.content.res.Resources.NotFoundException {
    try {
        // lookup field in class 
        java.lang.reflect.Field field = ?.getField(variableName);
        // always set access when using reflections  
        // preventing IllegalAccessException   
        field.setAccessible(true);
        // we can use here also Field.get() and do a cast 
        // receiver reference is null as it's static field 
        return field.getInt(null);
    } catch (Exception e) {
        // rethrow as not found ex
        throw new Resources.NotFoundException(e.getMessage());
    }
}

In Kotlin following works fine for me:

val id = resources.getIdentifier("your_resource_name", "drawable", context?.getPackageName())

If resource is place in mipmap folder, you can use parameter "mipmap" instead of "drawable".

int resourceID = 
    this.getResources().getIdentifier("resource name", "resource type as mentioned in R.java",this.getPackageName());

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);

I have found this class very helpful to handle with resources. It has some defined methods to deal with dimens, colors, drawables and strings, like this one:

public static String getString(Context context, String stringId) {
    int sid = getStringId(context, stringId);
    if (sid > 0) {
        return context.getResources().getString(sid);
    } else {
        return "";
    }
}

If I understood right, this is what you want

int drawableResourceId = this.getResources().getIdentifier("nameOfDrawable", "drawable", this.getPackageName());

Where "this" is an Activity, written just to clarify.

In case you want a String in strings.xml or an identifier of a UI element, substitute "drawable"

int resourceId = this.getResources().getIdentifier("nameOfResource", "id", this.getPackageName());

I warn you, this way of obtaining identifiers is really slow, use only where needed.

Link to official documentation: Resources.getIdentifier(String name, String defType, String defPackage)

• Kotlin Version via Extension Function

To find a resource id by its name In Kotlin, add below snippet in a kotlin file:

ExtensionFunctions.kt

import android.content.Context
import android.content.res.Resources

fun Context.resIdByName(resIdName: String?, resType: String): Int {
    resIdName?.let {
        return resources.getIdentifier(it, resType, packageName)
    }
    throw Resources.NotFoundException()
}

• Usage

Now all resource ids are accessible wherever you have a context reference using resIdByName method:

val drawableResId = context.resIdByName("ic_edit_black_24dp", "drawable")
val stringResId = context.resIdByName("title_home", "string")
.
.
.