Develop Reference

Way to group resources

I'd like to group my drawables in some way that doesn't involve some crazy approach (for example reflection on the generated R class).
For example I have 10 types of some object in a game. I'd like to load them all into an array without actually copying:
enemy[0] = resources.getDrawable(R.drawable.enemy_image_0)
enemy[0].set....
enemy[1] = resources.getDrawable.....
Is there some way to group them and load in a loop? Any way to do that without getting into how R is generated and changing its structure?

Is there some way to group them and load in a loop?
Use getIdentifier() on the Resources object (which you typically get via getResources() on your activity or other Context).
Since this, under the covers, uses a "crazy approach" (specifically "reflection on the generated R class"), and since reflection is not especially speedy, please cache these values where possible.

Finding the value of the reference name to R

I am doing some debugging in my application, mainly loading custom styles from styles.xml when my custom view is given a style="#styles/CustomStyle", and attributes such as custom:attribute="custom value"
I looked into the TextView source to see how Android loads styles/attributes and I am mimicking that. However I am not being passed any of my R.styleables through some of the calls to my constructors and so I am trying to peek in there to see which resources are coming in.
I am using obtainStyledAttributes() to load these key/value pairs into a TypedArray, however I am wondering if there is an easy way to convert the R.styleable.CustomWidget_customAttribute from the int that R reads, to its referenced name.
In essence, I want LogCat to say, "We've been given R.styleable.xxx" and not "We've been given 1487214712442"

Look at this method: http://developer.android.com/reference/android/content/res/Resources.html#getResourceName(int)
Return the full name for a given resource identifier. This name is a single string of the form "package:type/entry".

You most likely are not able to do this explicitly, as all resources are stored in a generated java class with no accessible reference to the original strings.
However, your best bet is override the toString() method for the R class.
See if something like that works.
Hope this helped!

Android: Loading multiple images

I have recently started developing a game in android, never used it before and was wondering if there is a simple way of getting a set of images loaded into the application. As my current implementation involves basically
Creating an int[] array,
Storing the values of each drawable into this array, (now this has to be hand coded, so if I add any more images it has to be added programmitically)
Then itterating through each item in the array and calling BitmapFactory to get the resource.
(Unfortunately I don't have the code with me as it is at home and I am at work, but that is the jist)
So 2 questions, is there a way of getting the drawables without having to put in each item manually to the int[] - ie looking for perhaps a file name prefix and then only loading the resource with the prefix?
Which leads me to my second question because I more than just these images in my drawable resource directory, is there a way to add extra organisation (folders) to manage the files better. As currently I have loads of images within the drawable file and how would I reference these sub folders/images.

You cannot have sub folders within the resources structure. Android depends on the folder layout to determine which resource to use in what condition (localization, different screen resolutions, etc).
I'm not sure why exactly you are trying to load up a whole bunch of images, but there are a couple of (slower) methods that allow you to look up a resource by string name. If you used a naming convention for your images you could look them up that way via [Resources.getIdentifier()][1]. However, in a game performance likely matters, so you are probably better off with a more manual approach using the int IDs directly since it is much more efficient.
[1]: http://developer.android.com/reference/android/content/res/Resources.html#getIdentifier(java.lang.String, java.lang.String, java.lang.String)

I am uploading a load of images as they will be shown to user for different items. Its not a system where responsiveness is critical so its okay in terms of what I want. Though...
public int getIdentifier (String name, String defType, String defPackage)
Since: API Level 1
Return a resource identifier for the given resource name. A fully qualified resource name is of the form "package:type/entry". The first two components (package and type) are optional if defType and defPackage, respectively, are specified here.
Note: use of this function is discouraged. It is much more efficient to retrieve resources by identifier than by name.
They suggest using the resource id but if I want to add a file later on then I have to re-compile the app to include the extra file, this is where it bugs me, as the pic gets associated to an item that I have in a string array. So I can add items to the array but not the images without a change of the code.
Surely there is a function to fix this?

Cannot get resource from android application

I am building an Android app, and I have a problem to get resource from string.xml.
I need to have a URL in String.xml that will be used several times through the app.
I tried Resources.getText("my_url"), but this does not work. Eclipse complains when I use this.
Do you think this is the best way to do ?

What you probably want is:
String myUrl = getString(R.string.my_url);
The getString() method is in Context which means that it's available directly in your Activity class since Activity is a subclass of Context. (The getString() method is also in Resources but it's easier to call on it directly on your Activity.)
What happens with your XML resources is that each is given a unique integer ID and this is added to the automatically generated R class as a public static final int. You then use these IDs to reference the resources. Have a look in the gen folder in your Eclipse project and you'll find the R class in there.

Do you ever refer this page: https://developer.android.com/guide/topics/resources/available-resources.html ?
If you want to retrieve the String represented by a resource ID, you can call the Context.getString() method.
Or, you have to post Eclipse's complains.

Using some kind of "external ID" for a View

i wrote a View class based on ViewSwitcher and now I want to write helper classes for the view like known form the ListView: ListAdapter, ListActivity and so on..
Regarding the activity class I ran into a problem. The ListActivity forces you to add a ListView to your activity with a fixed id: #id/android:list. In my base activity class i want to archive the same, forcing a special id so that my helper classes can access the view object.
As I'm writing a general lib that could be used in various projects I can't use R.id.foobar to get the view as there's no R class. The specific project will an own R.java.
So I peeked at the source code of ListActivity and found:
View emptyView = findViewById(com.android.internal.R.id.empty);
mList = (ListView)findViewById(com.android.internal.R.id.list);
if (mList == null) {
throw new RuntimeException(
"Your content must have a ListView whose id attribute is " +
"'android.R.id.list'");
}
Ok, I could write my on R class, put it directly into my package and try to access it in the same way but I've no clue what value the id should have or need?
Also I couldn't find any R class at android_frameworks_base/core/java/com/android/internal
And even if this problem is solved: How can the user of my lib access "my id" from his layout XML?
Thanks for your help! :)

I do not think this is safe, as Android has not supplied reusable widget authors with an ID range to use for your desired purpose.
Instead, do one of the following:
Have the reuser of your widget pass in the appropriate ID.
Use Resources#getIdentifier() to look up an ID in the R.* "namespace" given the string form of the name. If you go this route, be sure to cache this result, as it is a bit expensive to look up, apparently.

If you're creating a library APK that other applications can use, then consumers of this library cannot refer to its resource IDs in XML layouts.
When an Android application is started, it loads in and caches resource information from the application APK (resources.arsc), plus the system resources (i.e. those in android.R).
Your application, running in a separate process and as a different user ID, cannot directly read the resources from other APKs.
However, if you're just using the library for your own purposes, you should be able to get a greater level of access between your APKs by signing them with the same key, or specifying the same process ID in your manifest.

you can refer to raw resources supplied by a ContentProvider over a URI, I read Jpeg's out of Zips supplied by a ContentProvider that the user downloads in a seperate apk.
the uri is something like
android.resource://name.of.component/r_file_id
Then the ContentProvider can return the appropriate resource file identification to the calling app and it can then access the file over the URI.
edit: Same keys might be necessary for this to work