有没有办法从 strings.xml 定义静态字符串数组

Question

I want to declare a static string array using an array in strings.xml .

private static final String[] tip_types = getResources().getStringArray(R.array.tip_types_array);

but you cannot use getResources() 'in a static context'. Is there a way to do this or must I not use a static variable?

Obviously

private final String[] tip_types = getResources().getStringArray(R.array.tip_types_array);

works, but then the declared array is not static.

Answer 1

To fetch resources (including strings) you always need a context. When you create a static field, even within an Activity, you cannot access the instance fields and therefore there's no context available.

You have two options to solve the problem:

Method 1
You can create an Application class that stores the application context in a static field upon creation and get your string array using the application context.

private final static String[] tip_types = YourApplicationClass.getAppContext().getResources().getStringArray(R.array.tip_types_array);

Method 2
You can create a getter for your static variable where you pass a context. Like a singleton you check if the array is already resolved, and return it right away or fetch is using the supplied context. This has the advantage of lazy initialisation, the array is only created when it's actually needed.

private static String[] tip_types;

private static String[] getTipTypes(Context context) {
    if(tip_types == null) {
        tip_types = context.getResources().getStringArray(R.array.tip_types_array);
    }
    return tip_types;
}

Answer 2

The first one, you need declare a NfcApplication custom class which extend from Application class:

public final class NfcApplication extends Application {

    private static NfcApplication sApplication;

    public static NfcApplication getInstance() {
        return sApplication;
    }

    @Override
    public void onCreate() {
        super.onCreate();

        sApplication = this;
    }

    @Override
    public void onTerminate() {
        super.onTerminate();

        sApplication = null;
    }
}

The second one, then you can call the context by this way

private static final String[] ARRAY_LIST = NfcApplication.getInstance().getResources().getStringArray(R.array.label_unit_array_str);