Is it possible to do string substitution in Android resource XML files directly?

9
votes

In my android app, I have a large string resource xml file. I want to make reference and reuse declared resources values within String values. Is it possible to have the R class resolve referenced values (a la @string/db_table_name)?

<resources>
<string name="db_table_name">tbl_name</string>
<string name="ddl">create table @string/tbl_name</string>
</resources>

Is there a way of doing this. In regular Java world, some tools use ${varname} expression to resolve reference. Can this be done at all in Android?

4
androidandroid-resources
you probably dont need your db naming and query creation stuff in xml resources and they will not be dependent on localisation or device qualifiers - I would vote for having this stuff in a global project config file and maybe a static class for query creation - just a thought! Im not aware the above is possible is res files :) – Dori

4 Answers

12
votes

Add a %s to your second resource string (the one that you want to be dynamic) where you want it to be modified. i.e.,

<resources>
<string name="db_table_name">tbl_name</string>
<string name="ddl">create table %s</string>
</resources>

and in your code use getString() to work the magic,

getString(R.string.ddl, getString(R.string.db_table_name));
3
votes

It's indeed possible.

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE resources [
  <!ENTITY appname "MyAppName">
  <!ENTITY author "MrGreen">
]>

<resources>
    <string name="app_name">&appname;</string>
    <string name="description">The &appname; app was created by &author;</string>
</resources>

You can even define your entity globaly e.g:

res/raw/entities.ent:

  <!ENTITY appname "MyAppName">
  <!ENTITY author "MrGreen">

res/values/string.xml:

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE resources [
    <!ENTITY % ents SYSTEM "./res/raw/entities.ent">
    %ents;   
]>

<resources>
    <string name="app_name">&appname;</string>
    <string name="description">The &appname; app was created by &author;</string>
</resources>
1
votes

Yes, it is possible without writing any Java/Kotlin code, only XML, by using this small library I created which does so at buildtime: https://github.com/LikeTheSalad/android-stem

Usage

Based on your example, you'd have to set your strings like this:

<resources>
  <string name="db_table_name">tbl_name</string>
  <string name="ddl">create table ${db_table_name}</string>
</resources>

And then, after building your project, you'll get:

<!-- Auto generated during compilation -->
<resources>
  <string name="ddl">create table tbl_name</string>
</resources>
0
votes

Well, I don't think this is possible. Because once the resources are allocated android won't allow us to change them dynamically in the air. Instead you can try having your Strings in a separate class and change them as you run through your code.