CODEWITHSUNDEEP
androidresourcesstatic
ilomambo
ilomambo

Reputation: 8350

Is it possible to get resources inside a static context block?

I want to create a static Hash table to convert strings to integers. The caveat here is that I want to use strings I defined as resources in several lists in XML files.

I am able to write this, using only resources IDs:

public class MyActivity extends Activity {

private static Map<Integer, Integer> views = new HashMap<Integer, Integer>();
static {
    views.put(R.string.full_text, MessageTable.VIEW_FULL);
    views.put(R.string.only_text, MessageTable.VIEW_MSG);
    views.put(R.string.tag_text, MessageTable.VIEW_TAGMSG);
}

I get no errors, but what I would really need to do is something like this:

public class MyActivity extends Activity {

private static Map<String, Integer> views = new HashMap<String, Integer>();
static {
    views.put(getResources().getString(R.string.full_text), MessageTable.VIEW_FULL);
    views.put(getResources().getString(R.string.only_text), MessageTable.VIEW_MSG);
    views.put(getResources().getString(R.string.tag_text), MessageTable.VIEW_TAGMSG);
}

which gives me the following error in Eclipse:

Cannot make a static reference to the non-static method getResources() from the type ContextWrapper

The message makes sense, but what does not makes sense is that resources are unreachable from the static block, one would think static variables were custom created to make use of resources.
I guess I can populate the Hash table during the object constructor, but this would mean to do it in the wrong place.

Upvotes: 14

Views: 20941

Answers (5)

Jeremy Edwards
Jeremy Edwards

Reputation: 14740

One thing you can do is create an Application class and register it in your AndroidManifest.xml. Then override the onCreate method and set the Application class as a static reference and then touch the Activity class to run the static initializer. The Application class will be run as the apk is loaded into memory so it will always run before any Activity.

There are some significant drawbacks to this. The most obvious one I think of is if the system language changes and you have added translations to these resources; then you will have inconsistent strings because the application will use the default/whatever the language was when the application was launched. String resources are influenced by Android's resource management system so changes to things like orientation, system language, and screen dimensions can influence what these values are. That's the reason why Activities get reset when

In short, you're better off using constant Strings key-value pairs for this job. If you need to use string resources so you can handle translations better. I'd load them each time the Activity starts. Otherwise, you risk memory leaks and inconsistent string translations.

public MyApplication extends Application {

  public static Context GlobalContext = null;
  
  @Override
  protected void onCreate() {
    MyApplication.GlobalContext = this;
    
    // Touch the activity class.
    MyActivity activity = new MyActivity();
    // Throw it away by not using it.
    
    // invalidate handle to prevent GC leaks.
    GlobalContext = null;
  }
}

public class MyActivity extends Activity {
  private static Map<String, Integer> views = new HashMap<String, Integer>();

  static {
    Context context = MyApplication.GlobalContext;
    Resources res = context.getResources();
    views.put(res.getString(R.string.full_text), MessageTable.VIEW_FULL);
    views.put(res.getString(R.string.only_text), MessageTable.VIEW_MSG);
    views.put(res.getString(R.string.tag_text), MessageTable.VIEW_TAGMSG);
  }
}

Upvotes: 1

zapl
zapl

Reputation: 63955

getResources() (short for ~ MyActivity.this.getResources()) requires a context object which is not initialized at that time. Since context is only available after you hit onCreate you can't even do it at construction time of MyActivity.

The reason is that the activity manager which instantiates your MyActivity class has to determine the configuration (orientation, screen size, language, ...) before he knows which resources have to be extracted from the xml. -> Resources are not static and can't be accessed from static context.

So I guess there is no way around doing those operations in onCreate or later.

Edit: While you certainly can update the static HashMap (or a static Context) from onCreate I wouldn't recommend that since you can have several instances of the same Activity with possibly different / changing configurations. Also storing a static Context is a great way to create a Memory Leak

Upvotes: 12

Khurram Shehzad
Khurram Shehzad

Reputation: 1010

public Static Resources mResources;
public MyApplication extends Application
{
     @Override
     public void onCreate()
     {
           mResources = getResources();
     }

}

Once you have the static reference to the Resources, you can refer to it anywhere from the entire application. However i am not sure about whether this is gonna introduce a momory leak or not;

Upvotes: 8

Andre Mariano
Andre Mariano

Reputation: 308

I don't know what's the BEST way, But, for example, in my app, I have a Singleton (called GuiaUtil) that aways keeps my current Activity and Context.

private static Map<String, Integer> views = new HashMap<String, Integer>();
static {
views.put(GuiaUtil.instance().getAppContext().getResources().getString(R.string.full_text), MessageTable.VIEW_FULL);
views.put(GuiaUtil.instance().getAppContext().getResources().getString(R.string.only_text), MessageTable.VIEW_MSG);
views.put(GuiaUtil.instance().getAppContext().getResources().getString(R.string.tag_text), MessageTable.VIEW_TAGMSG);
}

Upvotes: 0

asenovm
asenovm

Reputation: 6517

You can always keep a static reference to the ApplicationContext. A possible way is described here: Static way to get 'Context' on Android?

Upvotes: 0

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