Develop Reference

android resource string %

now I encounter a doubt about % in android string resource. The question as follow:
If I want to use % symbol in other language, such as in chinese. I must add resource string formatted="false" in /values-zh-rCN/strings.xml.
Yes, the string tag must have ther formatted attribute.
However, it could not add this formatted attribute in /values/strings.xml in english language. it compile successfully, and work well.
Why?
I can't find any answer in android developer website.
ps: how i write Angle brackets in stackoverflow editor. I'm a freshman.
Java code:
autoDownloadLayout.findViewById(R.id.setItemContent)).setText(R.string.setting_auto_update_title_1_subtitle);
/values/strings.xml :
<string name="setting_auto_update_title_1_subtitle">Automatically download updates when connected to Wi-Fi, when the battery level is greater than 30% and CPU usage is less than 50%</string>
/values-zh-rCN/strings.xml :
<string formatted="false" name="setting_auto_update_title_1_subtitle">"仅在 WLAN 网络，手机电量高于 30% 且 CPU 占用率低于 50% 时，预先下载游戏更新包"</string>

It seems that Android Lint has different ideas when checking translated strings as compared to default strings. There's an open issue (Issue 74959) about this (although it's not exactly your problem). It would seem that technically you should be adding formatted="false" to the strings in /values as well as to those in /values-zh-rCN.
Alternatively, you could encode all literal percent signs as % (or %). That might be the simplest (and least risky) approach.

Where to store string values?In strings.xml or in constants class?

In android, we can store string values either in strings.xml file or in some constants class as static final variable.Is there some reason for selecting one over another in some circumstances?

In a nutshell:
value for use in code: use always constants class.Advantage: codes remain integrated and your package can be utilized in other projects/contexts. You can not do that with string.xml as it is not transported with your package.
value for display in UI: use string.xml. Advantage: you can use localization to display translated texts.
Some situation may arise when both option appears viable. You will have to then decide where are its related values are stored.

As a general rule, use the strings.xml because android uses that XML to enable translating your app into different languages, which it can't do with strings that are hardcoded.
The official android guide on localization say the following;
Move all strings into strings.xml
As you build your apps, remember not to hard code any string. Instead
declare all of your strings as resources in a default strings.xml file
which makes it easy to update and localize. Strings in strings.xml
file can be extracted, translated and integrated back into your app
(with appropriate qualifiers) without any changes to compiled code.
If you generate images with text, put those strings in strings.xml as
well, and regenerate the images after translation.
Strings that are not going to be displayed to the user in any way needn't be stored in the XML, because they will never need translating, and you probably don't want the android system tampering with them in ways you might not know about during runtime.

If the string value is used to display in UI store in Strings.xml Otherwise keep it in code. There can be JSONTags, Key for different api/Thirdparty libraries.These kind of things should be kept in code itself.

strings.xml it is used for localization and needs a context to retrieve the content of a String. If you need a java constant to be accessed in different classes, you a public static final String member. If the string is a message for the user you should use strings.xml

If strings represent text readable by user, and which could potentially be translated to other languages (names of buttons, labels, notification/error messages, etc.) then they should be in strings.xml (actually, it can be any file name you like, not just "strings").
If string is some constant which is used in the app internally (bundle/intent keys, fragments tags, etc.) they should be declared in class

It depends, if it is a text string that will be translated or displayed to the user then for 118n sake, you will want to put in into strings.xml.
However, if the string is something like a server url or api code then you'll want to store those in code as a public static final String

Plurals not working as intended in android

I am using Plural strings provided by android-sdk. I have used following code to create a plural string:
<plurals name="valuestr">
<item quantity="zero">Choose a value.</item>
<item quantity="one">%d unit.</item>
<item quantity="other">%d units.</item>
</plurals>
Java Code:
textView.setText(getResources().getQuantityString(R.plurals.valuestr,0,0));
When i am setting any value other than '0', this is working fine but when i am setting '0' it is showing '0 unit.'.
Please help!
Update
While searching more on the internet i came across a workaround which uses java.text.MessageFormat class:
<resources>
<string name="item_shop">{0,choice,0#No items|1#One item|1<{0} items}</string>
</resources>
Then, from the code all you have to do is the following:
String fmt = resources.getText(R.string.item_shop);
textView.setText(MessageFormat.format(fmt, amount));
You can read more about the format strings in the javadocs for MessageFormat

A post was recently made on G+ about this.
In short, it is because this will not pick the closest match by Integer ( 0 = zero), but because it will look for the best grammatical pick.
In your example, you use units.
The correct usage would be;
0 units
1 unit
2 units
Making, zero equal to pretty much any other quantity above 1
Read the full story here;
https://plus.google.com/116539451797396019960/posts/VYcxa1jUGNo

Plurals defined in <plurals> sections of resource files are only to be used for a grammatical distinction with respect to singular/plural strings. You should not use them for other display logic, as you did. You should add some checking logic in your code instead.
The Android developer's guide clearly states this:
Although historically called "quantity strings" (and still called that
in API), quantity strings should only be used for plurals. It would be
a mistake to use quantity strings to implement something like Gmail's
"Inbox" versus "Inbox (12)" when there are unread messages, for
example. It might seem convenient to use quantity strings instead of
an if statement, but it's important to note that some languages (such
as Chinese) don't make these grammatical distinctions at all, so
you'll always get the other string.
Your workaround - although working technically for your current implementation - does not appear like a clean solution either, in my opinion. Future business requirements may make it necessary to include more sophisticated logic than just displaying a different text. Or you may have a generic "no items selected" string in your resource file used at different locations, which could be reused only if you did not stick to your solution.
Generally, I would avoid using two different formatting techniques (String.format style formatter %d vs. MessageFormat style formatter {0} and pick one that you'd stick to in your whole application.

Performance at working with strings android

Could somebody tell me what is better in terms of performance?
Is it better to save 2 strings at string.xml, like 'abc' and 'abc:'
Or should I save only the first one and concatenate ':' when needed at Java coding ???

Very difficult to answer depending on what your strings will represent and what you need to append. Localization is also an issue, for example...
Dog // English
Chien // French
Hund // German
Using string resources allows you to create different resource files depending on the locale of the device and Android will automatically use the right localized string resource file. If all you need to do is append a single character such as : then you'll double every string for every language.
If you choose to only save the basic strings and append the character using code, then the code will be universal and you'll simply need to append the character to whatever localized word - potentially a lot more efficient.

Both from storage perspective and performance you should save only "abc";
getting extra data from disk takes far longer as some quick in-memory actions.
storing the same data twice is bad practice in general

If you have to concatenate multiple strings you should use StringBuilder - http://docs.oracle.com/javase/1.5.0/docs/api/java/lang/StringBuilder.html
It's much faster then using '+' or '.concat()'

Android: converting between Strings, SpannedStrings and Spannablestrings

I have a string resource called "foo". It may be a simple string... or it may contain HTML. This may change over time: I should be able to box it up as at least a SpannableString immediately upon reading whether it's HTML or not (but how??)
I want to get that raw CharSequence and first be able to display it as-is (the exact characters, not Android's "interpretation" of it). Right now I can't do that... toString() decides to rip out the parts it doesn't think I want to see.
I'd then like to be able to create a SpannableString from this and other Strings or SpannableStrings via concatenation using some method (none of the normal ones work). I'd like to then use that SpannableString to display the HTML-formatted text in a TextView.
This shouldn't be difficult, but clearly I'm not doing it right (there's very little info out there about this that I've found so far). Surely there is a way to accurately interconvert between between Strings, SpannedStrings and even Spannablestrings, without losing the markups along the way?
Note that I've already played with the somewhat broken Linkify, but I want better control over the process (no dangling unformatted "/"s, proper hrefs, etc.) I can get this all to work IF I stay in HTML at all steps, though I can't concatenate anything.
Edit 1: I've learned I can use the following to always ensure I get my raw string (instead of whatever Android decides it thinks the CharSequence really is). Nice... now, how to coax this into a SpannableString?
<string name="foo"><![CDATA[
<b>Some bold</b>
]]>
</string>
Edit 2: Not sure why this didn't work earlier, but... if foo1 and foo2 are strings marked up as above (as CDATA), then one can apparently do this:
String foo1 = (String)getResources().getText(R.string.foo1);
String foo2 = (String)getResources().getText(R.string.foo2);
SpannedString bar = new SpannedString(Html.fromHtml(foo1+foo2));
Curious: is there a more straightforward solution than this? Is this CDATA business actually necessary? It seems convoluted (but not as convoluted as never quite knowing what the resource type will be... String, Spannable, etc.)

I had the same problem. There are two solutions according to Google API Guides.
First is to escape < mark with < in the string resource. Unfortunately, String conversion removes the tag in the background.
Second is to use Format Strings instead of XML/HTML tags. It seems simpler, faster, and evades hidden conversion problems. getString(resource, ...) works like a printf(string, ...) here.
Both work and require some code to replace given part of the string anyway (handle tags or format strings). Enjoy! =)

It appears there isn't a more straightforward way to accomplish this.