NOTICE: Please save yourself some time and refer to the accepted answer, no need to read all the quesiton.
You may read the rest of the question and the answer I provided for an alternative (although less sophisticated) method.
Also, you may want to take advantage of the fix for the background glitch in Android 2.X, by adding the related piece of code to your preference activity class.
Background
Being a newbie to Android coding, but somewhat experienced in other programming languages/frameworks, I was expecting my walk to Android application coding would be a rather pleasant one. It was so, until I stumbled upon this problem:
Eclipse wizard for Android projects suggested I could reach a 95% of devices if I set my minimum API to 8 (Android 2.2). I didn't need to do any fancy things with my app anyways, so I thought, "sure, why not?". Everything was okay, except occasionally I'd find several methods/classes that were deprecated in most recent API versions, and so I had to devise ways to keep using the old ways for old devices, and try to use as much as possible the new ways for newer Android versions. This is one such occasion.
After using the Eclipse wizard for creating a preference activity, I realized that the Eclipse precompiler/parser/checker(or whatever it's called) Lint, would complain about not being able to use the new ways of creating/managing preferences in older API versions. So I thought, "all right, screw the new ways. Let's do it old way and since new API versions are supposed to be backward-compatible, it should be okay", but it wasn't. Old way used methods/classes that are marked as deprecated; which, to me, means, even though they'd still work in current API, they'd stop working at some point in future releases.
So I started searching for the right way to do this, and finally hit this page: What to use instead of "addPreferencesFromResource" in a PreferenceActivity? where Garret Wilson, explains a way to use old preference screen resources in a way compatible with the new ways. It was great, and finally had the feeling I could move on with my app coding, except it wouldn't work when targeting older APIs, as it was using newer APIs code. So I had to devise a way to make it work for both old APIs and newer. After tinkering with it for a while I managed to find a way, by using precompiler(or whatever it's called) annotations and the great getClass().getMethod() along with exceptions.
Everything seemed to work flawlessly until I created a preference sub-screen. It was displaying correctly in newer Android versions, but when I tried in older ones, I could merely see a black screen. After much searching, I found this page which explains the issue: http://code.google.com/p/android/issues/detail?id=4611 This is apparently a known glitch that's been around several Android versions for a good while. I read the whole thread and found several proposed solutions to the problem, but I really didn't like entirely any of them. I, for one, prefer to avoid as much static stuff as I can, and do things programmatically. I prefer automation over repetitive work. Some solutions suggested to create sub-screens as parent screens, then adding them onto the manifest file, and calling them from the parent screen through an intent. I'd really hate having to keep track of those things: entries in manifest, separated screen resource file, intents... So that was a no-no for me. I kept looking and found a programmatic approach I liked much better... only to find that it didn't work. It consisted of iterating through the whole view tree of the preference screen and assigning a proper background to preference sub-screens, but it just didn't work because, as I later found out after much debugging, preference sub-screens views are not a child of preference screen views. I had to find a way to achieve this myself. I tried as many things as I could think of, researched and researched to no avail. I was at the verge of abandoning at several occasions, but after some two weeks of continued effort and much debugging I found a workaround, which I posted in comment #35.
Opinion
It really isn't the perfect solution/approach, and I'm aware of several of its drawbacks, but it's one that works, so I decided I would share it. Hopefully I'm not being too ridiculous in my enthusiasm to share what has taken me what I'd consider quite a lot of effort, as I'm aware it's not that great of an issue, that any experienced coder could solve. But hey, I think sharing knowledge makes me a bit better, no matter how much I brag, than an experienced coder who keeps everything to himself. Just sharing my opinion, because I can't believe nobody ever had this problem before, but I do believe many have had it and didn't bother to share their knowledge.
I present you in the answer with a proposed class to use over several versions of Android, and some suggestions on its usage. I'm open to discussion and contributions to make it a better class.
Known issues:
- Parent screen Decor view background is cloned onto child screen Decor view background, which apparently isn't the normal behavior.
Status: dismissed until somebody comes up with a good reason to fix this - Crashes upon screen rotation
Status: Fixed.
Probably related to resource visibility by newer API implementation (inner class PF)
Apparently inherited classes from preferenceFragment need to have all their members static. I guess it makes sense if you're supposed to inherit every time you need to use a new fragment
You can use this class to display a preference screen in all Android versions from 2.X to 4.X, by feeding it with a preference screen resource.
You may use it directly by renaming it if you like, but I'd suggest you to add it to your project as is, and inherit from it, which is much cleaner if you need to work with several parent preference screens.
If you'd like to use it directly, just replace prefs value with your preference screen resource ID.
If you'd like to inherit from it, you should do it like this:
ALWAYS call setPrefs(int) before calling super.onCreate(Bundle)
If, for some reason, you'd just like to take advantage of the glitch-fix and create preferences on your own, you may either just copy the glitch-fix code into your own preference activity, or inherit from the class and catch the PrefsNotSet exception as follows:
And finally, the class:
If you are on the latest ADT plugin, there is an option to easily create a preference Activity that supports most older Android versions as well as all the new ones.
Then choose SettingsActivity
The Activity created will take take care of working with both high and low API versions since it uses if statements to choose the appropriate method of displaying the preferences.
EDIT
A good point was brought up: Phone-Sized devices, regardless of API version use the old
PreferenceActivity
methods.The quickest way to get API 11+ devices to use
Fragments
is to remove!isXLargeTablet(context);
fromisSimplePreferences()
However, now the user has more navigation to do.
This is because
onBuildHeaders()
is called.To get rid of this, we will need to make our own PreferenceFragment that adds each xml resource.
If you can determine the screen size from outside the
Activity
that launches the settings, you can specify a fragment for it to launch viaEXTRA_SHOW_FRAGMENT
Or you can have the
SettingsActivity
determine whether or not to show this Fragment (assuming you're happy with theisXLargeTablet()
method.Change
onBuildHeaders()
to:Add this method:
And in
onPostCreate()
add the method call.This should now use non-deprecated calls from API 11 onwards.
Well, working with the autogenerated SettingsActivity got pretty old pretty quickly. One has to scroll up and down past boilerplate code - moreover it's full of yellow warnings and I hate yellow (deprecated warnings can't be avoided altogether though - see What to use instead of "addPreferencesFromResource" in a PreferenceActivity?, where also the matter of how to make cross API
PreferenceActivity
is touched also - and Was PreferenceFragment intentionally excluded from the compatibility package? for a discussion). And also you may easily get an NPE - did you know thatonPostCreate()
is actuallyonPostStart()
- sofindPreference()
returnsnull
inonStart()
.Now there are solutions involving reflection but reflection is to be avoided (like hell it is) - and since we are not interested in pre 2 versions of android reflection can be avoided (see Is checking SDK_INT enough or is lazy loading needed for using newer android APIs ? Why?). Also there are solutions involving choosing a class at runtime - but having 2 classes sucks and is not OOP anyways (for those and other solutions see the answer to related question: PreferenceActivity Android 4.0 and earlier).
So I came up with an abstract base class, which is the correct Java and OO way of doing things (except if you need Eclair and below where you do need reflection and/or lazy loading of classes to avoid
VerifyErrors
), where I moved the autogenerated boilerplate code:And a sample implementation:
So the main idea is you provide an xml for preferences with headers:
where:
and
PREF_HEADERS_XML
:and setting up the simple preferences in
buildSimplePreferences()
I am interested into making this into a more general API - probably including the
sBindPreferenceSummaryToValueListener
- so ideas welcome.Ah, yes, the sBindPreferenceSummaryToValueListener fluff: