Difference in retrieving String and String Array resources?

Question

I'm new to Android and trying to understand the code I wrote from a tutorial. Meanwhile, I'm referencing the documentation whenever I want to really understand something.

The documentation in question

That page discusses string resources.

For a string, under the String section it states I could retrieve a string defined in an XML file like this: String string = getString(R.string.hello);.

XML in question:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string name="hello">Hello!</string>
</resources>

Now, for a string array, under the String Array section it states I could retrieve a string string array defined in an XML file like this::

Resources res = getResources();
String[] planets = res.getStringArray(R.array.planets_array);

XML in question:

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <string-array name="planets_array">
        <item>Mercury</item>
        <item>Venus</item>
        <item>Earth</item>
        <item>Mars</item>
    </string-array>
</resources>

How come I have to do Resources res = getResources(); for a String Array, and not for a String in an XML file?

Would String[] planets = getStringArray(R.array.planets_arry); not work? Do resources have more methods, namely for more complex cases like String Arrays? is getString so simple it is fine to not need it under a resource? Where could I find a list separating what requires me to do Resources res = getResources(); versus what doesn't require that?

Lastly, does getResources get me every single resource in my Android project irregardless of what XML file it may be in?

Answer 1

How come I have to do Resources res = getResources(); for a String Array, and not for a String in an XML file?

getString() is a method of your Context object (mostly an Activity but could also be a Service). The code for that method is:

public final String getString(int resId) {
    return getResources().getString(resId);
}

Meaning getString() is just a convenience method that the Context class offers. In the end both calls do the same, namely retrieve a resource through the Resource object.

Would String[] planets = getStringArray(R.array.planets_array); not work?

No because Context doesn't have a convenience method to retrieve String[].

Do resources have more methods, namely for more complex cases like String Arrays?

Yes. See http://developer.android.com/reference/android/content/res/Resources.html. I leave if up to you to decide whether they are more complex than getStringArray.

is getString so simple it is fine to not need it under a resource?

Resource does have a getString(int) method: http://developer.android.com/reference/android/content/res/Resources.html#getString(int)

Where could I find a list separating what requires me to do Resources res = getResources(); versus what doesn't require that?

There's no such list. The JavaDoc for Context will tell you what convenience method you got: http://developer.android.com/reference/android/content/Context.html

Lastly, does getResources get me every single resource in my Android project regardless of what XML file it may be in?

Only if it's in a resource xml file. Layouts or Drawables can't contain String resources.

Answer 2

The call getString() is essentially the same thing as getResources().getStringArray(), as mentioned here the method getString() is just a convenience method, because it's used so often.

public final String getString(int resId) {
    return getResources().getString(resId);
}

I'll also add that you can't use getStringArray in other resource files, like XML layouts, where getString() can be.