When to use getString()

Question 1

The question is easy to misinterpret.

If you are in a valid context (like an Activity), there is no difference, because the context has a reference to the resources, so it can resolve a getString(int); directly, which returns a String.

Adding more information for your peace of mind.

If you can use getString directly, go ahead and do it. Now sometimes you might need to use getResources() because it contains a lot of helper methods.

This is the Android source code for getResources.getString():

/**
     * Return the string value associated with a particular resource ID.  It
     * will be stripped of any styled text information.
     * {@more}
     *
     * @param id The desired resource identifier, as generated by the aapt
     *           tool. This integer encodes the package, type, and resource
     *           entry. The value 0 is an invalid identifier.
     *
     * @throws NotFoundException Throws NotFoundException if the given ID does not exist.
     *
     * @return String The string data associated with the resource,
     * stripped of styled text information.
     */
    public String getString(int id) throws NotFoundException {
        CharSequence res = getText(id);
        if (res != null) {
            return res.toString();
        }
        throw new NotFoundException("String resource ID #0x"
                                    + Integer.toHexString(id));
    }

Neat huh? :)

The truth is that the Resources object does a lot more than just "get strings", you can take a look here.

Now compare with the Activity version of getString():

Return a localized string from the application's package's default string table.

So in summary, other than the fact that the Resources object will be stripped of any styled text information. and that the Resources object can do a lot more, the end result is the same. The Activity version is a convenient shortcut :)

Question 2

The methods are same. Logically, there's not a difference. you can assume, it does exactly:

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

The only difference I know is that getResources() may be required to fetch other apps resources as object. getString() will access your own resources.

Question 3

If you use it for TextView there are two methods setText() in it. One takes (CharSequence string) and another takes (int resId). That's why your both variants work.

Generally I would recommend to define all strings in strings.xml files and get them via getResources().getString(int resId) in the code. Having that approach you'll be able to easily localize your app. You can read more about app resources here

Question 4

Very Basic difference.

R.string.some_text = return ID integer, identifying string resource in your space
getResources().getString(R.string.connection_error) = Will return you actualy string associated with ID `R.string.connection_error`

They both can be made use in Android system, where many of widgets can take directly id or value of a resource. Practically there is no difference in value returned only difference is is the Term Context, from you activity context is available to you hence calling getString directly routes to resources for this context, while from classes where context is not available say from a Adapter, you will need to first access the Context, then the resource associated with the context and at the end the String so you write getContext().getResources().getString(R.string.connection_error)

I hope it clears your confusion.

Question 5

One good reason is about formating & styling like :(http://developer.android.com/guide/topics/resources/string-resource.html#FormattingAndStyling)