如何在Android中的xml中为字符串资源指定空值？

Question

In my values.xml, I have some string resources. But sometimes, I want to have a null value for that string resource for specific reasons.

How do I specify that string to have a null value?

values.xml:

<string name="default_item_0">Some String</string>
<string name="default_item_1">@null</string>

Java code:

String item0 = context.getString(R.string.default_item_0);
String item1 = context.getString(R.string.default_item_1);

Expected:

String item0 = "Some String";
String item1 = null;

Actual:

String item0 = "Some String";
String item1 = "@0";

I tried the @null value, but it returns a string of @0 instead.

Is it possible to have a null value in xml?

Answer 1

As you know resources exist because they're supposed to be "something NOT null" , and @null is simply a reference resource with a zero-value id .

Is it possible to have a null value in xml?

Null value for string resources? No and honestly it doesn't seem reasonable

But in this case with your specific reasons I suggest you to add an empty string to resources:

<string name="empty"/>

Then you can check if it is empty or not :

String str = getString(R.string.empty);
    if (TextUtils.isEmpty(str)) {
        //do something
    }

PS: Earlier I used this approach to map indices to the correct items of an array, as you guess in my case some indices were skipped so I had to skip some array items as well.

Answer 2

You can try with matches

Tests whether this string matches the given regularExpression. This method returns true only if the regular expression matches the entire input string.

if(getResources().getString(R.string.default_item_1).matches("@null")) 
{ 
     // Your logic
}
else
    {
     // Your logic
    }

If you need to format your strings using String.format(String, Object...), then you can do so by putting your format arguments in the string resource.

Courtesy dynamic String using String.xml?

Answer 3

You can use method for this.

 public static boolean isNullString(String string) {
    try {
        if (string.trim().equalsIgnoreCase("null") || string.trim() == null || string.trim().length() < 0 || string.trim().equals("")) {
            return true;
        } else {
            return false;
        }
    } catch (Exception e) {
        return true;
    }
}

Use this method as

if(isNullStrind(your string value){
//true
write your code
}else{
//false
}