I'm just wondering, if the latest Android SDK installed on a device contains code of all the previous versions as well?
So if I target API level 10 in my app and install it on a device with Lollipop, will it just take and use Gingerbread SDK exactly as it was 3 years ago?
Or is there just one codebase for all versions with a lot of checks and switches which is then run by some kind of compatibility mode picking the correct code and enabling methods of the version of SDK I target?
I read the article about android:targetSdkVersion specified in Manifest but still would like to know how this works internally.
Ok, I just surfed a bit around on the source code (which you can find here: https://github.com/android/platform_frameworks_base). I'm not an engineer of the Android framework, I was just curious about your question and here is what I found.
It does not contain all the different versions of source code. You can imagine that this would result in a nightmare if more and more versions become available. Foremost, you would have different (buggy) versions of the same method without fixing them just to keep them the same.
In the source code, you can find places like these: (see https://github.com/android/platform_frameworks_base/blob/59701b9ba5c453e327bc0e6873a9f6ff87a10391/core/java/com/android/internal/view/ActionBarPolicy.java#L55)
public boolean hasEmbeddedTabs() {
final int targetSdk = mContext.getApplicationInfo().targetSdkVersion;
if (targetSdk >= Build.VERSION_CODES.JELLY_BEAN) {
return mContext.getResources().getBoolean(R.bool.action_bar_embed_tabs);
}
// ...
return mContext.getResources().getBoolean(R.bool.action_bar_embed_tabs_pre_jb);
}
So the Android developers do the version check in the code where necessary. But these checks are not as necessary as you think (I guess). What's the reason for changing a method?
method is buggy: All they need to do is fix the bug. Tests will make sure that the general behavior of the method keeps the same
method is deprecated: The guys can not remove the method, all they can do is mark it as deprecated and hope for the best. Compilers will do the rest.
method behavior has to change: Well, I guess that is something they can not do easily. They can work around with version codes (which is pretty ugly and becomes a maintenance nightmare), or they just introduce a new API. That's the reason why you'll find a lot of APIs just doing the same
If you have write down a code with latest android sdk and install it in your device. It means actually you are using latest android.jar(you can see android.jar in your project) file while compiling/Executing code.
Now If you install your application in ginger bread device then android.jar(latest) has a backward compatibility(if required) to run code in Gingerbread device.and if you define target sdk version 10 and running app on Higher API level ,then it will run smooth except your compatibility behavior disable in respective device other than targeted devices.
Related
Note: There is a question with a similar title however this is not a duplicate. If you wonder what question that is: question link The option is already enabled in my IDE.
Recently we have updated an app with some bug fixes but one of the changes caused a critical crash, depending on a method that has been added in API 29, and Android Studio didn't warn me about it which led to an unavoidable crash at user base.
If you wonder, I also have API 29 documentation downloaded in IDE, so I can see the sources, javadocs in it.
The method I've used is Parcel.writeBoolean(val) method. According to the documentation, this was added in API level 29 (I don't know why it's added this late but it was), however this is how it looks when I use it in the IDE. (Minimum API version is 21)
There are no warnings about the API usage. Hence I casually used it and it lead to a huge crash rate in our app.
Is there a way to check every method based on its API level? On normal cases (such as using Context.getSystemService(Class clazz) the IDE gives a warning that it is added in API level 23) it seems to be working, but on really newly added methods, it sometimes skips the warning.
Do I need to check every Android framework based method before using it? Or is there something that do this task properly? Any help is appreciated, thanks.
Well, apparently I had an old version of Android Studio (3.5.1), updating it to 3.6.1 solved the issue.
Problem: I made an app for the Android 5.1 Platform. I now need to make it compatible with ICS. What is the best way to accomplish that?
I know that I should have set the minSDK to ICS when I started the project, but now I essentially want to change the minSDK in the middle of the project.
I am using android studio as the IDE (latest release).
Since you using minSdk=22 from the beginning Android Studio does not alarm you about incompatibilities issues.
First of all you should change midSdk of course. Than review all the sources for incompatibility warnings like 'using new android api'. Such analysis easily can be done with 'lint'. When you find one do not suppress it with #TargetApi, but write additional code to work around.
Something like:
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.LOLLIPOP) {
do_your_magic();
} else {
add_additional_code_for_pre_lollipop();
}
Looks ugly but this is the world we live in)
Also you may find some 'deprecated methods' warnings, leave them alone, they does not matter for your question.
There can be some other cases. Maybe it will be necessary to include support-v7 and change your Activities. Maybe you using libraries that do not support ICS. Not knowing project details can't help much.
I am making application with target SDK set to 17 and min to 8.
So for some features I have to use Support library v4
Question is how can I test it works on older devices?
I am testing on my phone - which has 4.2.2; and I don't have others with older ones
Will creating emulator with 2.3.3 be true test?
tnx
Update
Just for example: I use Fragment in my code (from android.app, not from support library) - even if my minSDK is 4 - I don't see any warnings...should I?
Yes. It is an emulator (not a simulator) so it is very similar to running your code on the corresponding phone.
Another good practice is to run the Lint tests from times to times, they can detect many common mistakes in your code (including compatibility).
Your ide (both Eclipse & Android Studio plugins do this) will also display warning for obvious calls to functions that don't exist at your chosen min API level.
Most of the time emulator behave same if we consider layout view and
other stuff like look and feel performance , but that can be
difference in case of speed performance and sound quality
.
I found one online tool which are providing that service please go through that link , https://appthwack.com
apache lint (from tools) is the answer - shows all problems
I have an app to release which works on all android screen-sizes (except smaller) and densities above SDK version 2.0.
It will also run on extra large screens.
Currently I have added this:
<supports-screens
android:largeScreens="true"
android:normalScreens="true"
android:smallScreens="false"
android:anyDensity="true"
/>
But I also need to add android:xlargeScreens="true" , to allow it visible in android market on extra large screen devices, since by default it is false.
But to add android:xlargeScreens I need to change my eclipse targetsettings to 2.3 as this attribute was added from API level 9.
So what should I do with my target compilation settings for this scenario ? Should it be 2.3 while compiling ? If yes, then will the app not give any problems while running on devices with 2.0 version ?
Yes you need to change the uses sdk to 2.3 but make sure that you are not using any newer apis which are not in 2.0 or whatever your minimum supported sdk version is. Or in case you want to use them you have to use reflection.
But more about how to use the sdk versions is here and more about uses-sdk is here.
I do the same in my application and make sure you test your application in both[all] the versions before you release.
Best,
Achie.
I'm moving this from the comments to make it more clear for others looking at this question in the future.
When supporting both old and new versions of Android it can be confusing how applications manage to run despite many things change with in the frameworks during each new release, I'm going to try and clarify this here.
An application written for the 1.5 sdk can only call functions that exist for that API level, so for instance the multi touch api's didn't exist in 1.5 and never will. Now you say "Ok but I don't need to call any newer APIs, I just want my app to work in 2.3 and have a2sd support" And I say "Ok, just change your targetApi in the manifest, set the minSDK and compile against 2.3 and you're good to go."
Now why does that work? What if the onMeasure() method for ListView was changed in 2.2 and now calls betterCalculateFunction() within onMeasure()? Why does my app still work?
This is the advantage of late binding in Java. You see, Java is never compiled until it reaches a device and is running, what you are doing in Eclipse is converting it to byte code which contains a bunch of byte code instructions that are later interpreted by the device. The byte code will NEVER contain a reference to betterCalculateFunction() though (unless you directly call it. Calling onMeasure() is indirect). This can happen because when your code is running on the device it gets linked against the Android framework on the device and your code calls onMeasure() directly because it is a public outward facing API. The path of execution will then enter the framework and call whatever it needs to, then once its done return to your code.
So on 1.5 you might see
doStuff (your code) -> onMeasure
(public API) -> done
and 2.2
doStuff (your code) -> onMeasure
(public API) ->
betterCalculateFunction (private
function) ->done
Now if you need to call functions that may or may not exist depending on API level then I suggest you look at a related answer of mine here stackoverflow: gracefully downgrade your app
Hope that clears some things up.
I haven't tried 2.3, but that's what I do with 2.2.
I compile for 2.2 and test on 1.6 to make sure everything works how I'm expecting. I haven't run in to any issues with it.
To double check, set your target for 2.3 and then setup an emulator for a lower rev version to make sure it all works.
The default value for android:xlargeScreens is true, so you don't have to change anything - it's on by default, as long as your minSdkVersion or targetSdkVersion is higher than 4.
http://developer.android.com/guide/topics/manifest/supports-screens-element.html
Here is an official Android developer blog explanation of how this works:
http://android-developers.blogspot.com/2010/07/how-to-have-your-cupcake-and-eat-it-too.html
In summary: you can use the newest XML whilst still supporting the older OS versions in a back compatible way.
While reading this blog post I guess I have an answer on my old question. An extract below (which is for another manifest attribute "requiresSmallestWidthDp" introduced from 3.2):
"The catch is that you must compile your application against Android 3.2 or higher in order to use the requiresSmallestWidthDp attribute. Older versions don’t understand this attribute and will raise a compile-time error. The safest thing to do is develop your app against the platform that matches the API level you’ve set for minSdkVersion. When you’re making final preparations to build your release candidate, change the build target to Android 3.2 and add the requiresSmallestWidthDp attribute. Android versions older than 3.2 simply ignore that XML attribute, so there’s no risk of a runtime failure."
For different screens you have to create multiple apk then it reduces size of your application.In each application's manifest you have to define according to following link.
http://developer.android.com/guide/practices/screens-distribution.html
I want to implement a gateway for handling outgoing calls.
In the latest Android versions 2.x I can do this easily with the hidden ACTION_CALL extra string:
"com.android.phone.extra.GATEWAY_URI"
But in earlier versions, like 1.6, I don't know how to do it. It must be possible because Google Voice is doing it. Can someone please help me?
Thanks,
Emmanuel
Hey Emmanuel,
76% of Devices already run Android 2.x maybe that effort is wasted. Gingerbread is expected to come out by the end of the year, which will push the percentage of 1.6 Devices further down. In less than half a year Android 2.x and higher will by beyond the 80% mark. Just look at the Platform version distribution http://d.android.com/resources/dashboard/platform-versions.html. Maybe have a look at the source code in the Android Open Source Project.
I found the string you mentioned in the InCallScreen.java. Maybe that gives you a way to dig into the older source code to try to figure out if you can access it through some undocumented APIs. But my suggestion would be to not bother with those last 25% of 1.6 devices they will disappear fast.
[Update]
Since it is a requirement to make it work, I would suggest you recompile the Phone App from the git repository and make it debugable that way you can see exactly what is going on. Probably having an ASOP Device running 1.6 would be your best bet to drill deep into how Android is doing it. Basically you would have to back port all the code that is involved in this feature in 2.x back to 1.6. From a time to market perspective I would suggest get the app out with 2.x support and release a second version that is tailored for 1.6. Delaying the release just because of 1.6 seems to be a bad business idea.
That code using the GATEWAY_URI was definitely added in Eclair.
Looking into AOSP, in packages/apps/Phone/src/com/android/phone/InCallScreen.java, that bit of code is completely inexistant in Donut :
// If a provider is used, extract the info to build the
// overlay and route the call. The overlay will be
// displayed the first time updateScreen is called.
if (PhoneUtils.hasPhoneProviderExtras(intent)) {
mProviderLabel = PhoneUtils.getProviderLabel(this, intent);
mProviderIcon = PhoneUtils.getProviderIcon(this, intent);
mProviderGatewayUri = PhoneUtils.getProviderGatewayUri(intent);
mProviderAddress = PhoneUtils.formatProviderUri(mProviderGatewayUri);
mProviderOverlayVisible = true;
if (TextUtils.isEmpty(mProviderLabel) || null == mProviderIcon ||
null == mProviderGatewayUri || TextUtils.isEmpty(mProviderAddress)) {
clearProvider();
}
} else {
clearProvider();
}
I cannot see any alternative. You're best luck maybe to take that Phone application from Donut, add what you need and release it as a new Phone application on Donut devices...