Packaging Android resource files within a distributable Jar file

Since Android makes the R class automatically with resource files under the /res folder, using the R class as final static is impossible.

I found a nice solution to use a jar file with the res files. Here is how I did it:

1. In your source code which will be exported in the jar file, don’t use R variable because it will be replaced with a final static memory address in compile time.
   Instead of using R, I made my own method below:

   public static int getResourceIdByName(String packageName, String className, String name) {
       Class r = null;
       int id = 0;
       try {
           r = Class.forName(packageName + ".R");
   
           Class[] classes = r.getClasses();
           Class desireClass = null;
   
           for (int i = 0; i < classes.length; i++) {
               if (classes[i].getName().split("\\$")[1].equals(className)) {
                   desireClass = classes[i];
   
                   break;
               }
           }
   
           if (desireClass != null) {
               id = desireClass.getField(name).getInt(desireClass);
           }
   
       } catch (ClassNotFoundException e) {
           e.printStackTrace();
       } catch (IllegalArgumentException e) {
           e.printStackTrace();
       } catch (SecurityException e) {
           e.printStackTrace();
       } catch (IllegalAccessException e) {
           e.printStackTrace();
       } catch (NoSuchFieldException e) {
           e.printStackTrace();
       }
   
       return id;
   }
   

   For example, if you have a layout named main.xml, you can get it by calling the method:

   int id = getResourceIdByName(context.getPackageName(), "layout", "main");
   

   If you have a string whose id is “text1”, you can get it by calling method

   int id = getResourceIdByName(context.getPackageName(), "string", "text1");
   

   This method gives you your resource id at runtime. It uses the reflection API to get the status of R at runtime.

   By using this method you can avoid using the R variable.

2. Copy your res files to your target project.

3. Build.