Android application limiting features to support backwards compatibility - android

I have an Android app that has a minimum API level of 4 (Android 1.6) and I have some users who use this version of Android. However, I would like to implement a feature that uses NFC, which requires Android 3 or higher (API level 9+). This means that I would have to change the minimum API level in my manifest file, which will alienate users using older versions of Android. So is there a way to programmatically disable the feature that uses NFC if the device is incompatible and still allow the use of other features instead of locking out users using older versions of Android?

Set the min-sdk to 4 and the target-sdk to 9 and use something like this in your code:
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB){
//your API-9 specific code here
}else{
// an alternative code
}
this for the java part, in XML the newer attributes are ignored so its safe to add what you need

Read this http://developer.android.com/resources/articles/backward-compatibility.html . You can check if method exists using reflection API. Read previous questions: Check if method exists

You need yo encapsulate API level specific code to external classes and use reflection for calling them (using interface for example)

Related

Android Application: Stop using Deprecated API's on new API level enabled device

Well we started an application with support from API Level 8 i.e Froyo verison. Now we being on API level 18 Jelly Bean version, how do we stop using deprecated API's on my application.
One Example
Dialog(API 1) vs DialogFragment(API 13)
Following are in my mind
1)Use Android Support Library Good way to go?
2)Have a runtime API level check as below, is this a healthy habit?
if (Build.VERSION.SDK_INT==Build.VERSION_CODES) {//Some API Level
run a code
}else if(){
run a code
}
3) Use reflection?
4)Have separate code base to each API level,makes no sense.
5)Does Palystore allows us to uplaod multiple Apk's based on API level.Or the complete control is on uses-sdk manifest value.
<uses-sdk android:minSdkVersion="integer"
android:targetSdkVersion="integer"
android:maxSdkVersion="integer" />
What will be the best way use latest API's with only one code base and make one APK and inturn have backward comparability support.
Inputs will be much appreciated.
One Example Dialog(API 1) vs DialogFragment(API 13)
Dialog is not deprecated. Ways of using Dialog may be deprecated, such as the old-style managed dialogs.
Use Android Support Library Good way to go?
Generally, yes.
Have a runtime API level check as below, is this a healthy habit?
Yes, though usually you use >= or <=, not ==, to drive behaviors for a range of API levels.
Use reflection?
I wouldn't.
Have separate code base to each API level,makes no sense.
Does Palystore allows us to uplaod multiple Apk's based on API level
In some extreme cases this may be required. Most apps should not need this.
What will be the best way use latest API's with only one code base and make one APK and inturn have backward comparability support.
That is impossible to answer in the abstract.
Why not upload the existing application as a "legacy version" of the application, that supports older version of the app, and continue to develop the existing application for newer devices?

Do I have to write explicit code to ensure the backward compatibility?

If I specify the minimum SDK as 2.0 and the target SDK as 4.1,will I have to write explicit code to ensure backward compatibility. Like if I want to use a gesture detection feature introduced in SDK level 7 and I set the target as 7 and minimum to 3. I am asking will I need to write explicit code(which doesn't include the gesture detection features) so that it runs in targets less than 7 but greater than 3?
Yes, you will have to avoid calling future APIs when running on older versions of Android. You can organize your code to select an appropriate code path at runtime, depending on the version of your OS.
An example of how to preserve backwards-compatibility when using a new API.
Yes, you will need to, but I don't see any logical reason to still support any API before 8 (2.2).
It's literally 1.6% of the market. It's not worth the effort to maintain and support such early versions any more.
That said, if you need to do version specific code, this is the way to handle it:
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ECLAIR) {
//Use API 7+ code
} else {
//Use backwards compatible code
}
You should check out the Android official site on how to guarantee backwards compatibility to minimum level 4 (which is negligible up until api level 7 anyway. The slightly more significant share is usually api level 8 upwards), and always use the latest support library.
Of course there are some minor code changes (such as getSupportFragmentManager() in replace of getFragmentManager(),etc). The worst you it can happen is NoSuchMethodException so you have to be real careful not to call API's that does not exist in lower platforms. The sdk should be very clearly advising that when it happens.

Dynamically choose api in mono for android

Is there any way to detect the current version of android and use one code path for one version, and another code path for a later version?
Something like ClipboardManager, there is a new version in API level 11, but the only way of accessing this new class is by telling mono for android that the minimum requirements is API level 11.
I "think" you can get around this using java reflection, but I imagine this wouldn't work when using Mono for Android. Has anyone got any advice on how you can use both ClipboardManager's, the early one on earlier versions, the later one on later versions, without setting the API level as 11 or higher.
This is a generic example, not limited to ClipboardManager. I am sure I will come across more classes that I could optionally use if it is available.
Sure there is. Just make sure to set your target API level in the manifest.
When wanting to use API 11 for instance you could do something like this:
if ((int)Build.VERSION.SdkInt >= 11)
{
//Execute API 11 and up code here
}
However if you are using methods and classes that are only present in API 11, VS might complain that it cannot find them, so you can surround them with a pre-processor symbol like:
#if __ANDROID_11__
// your API 11 and up code here
#endif

android - SDK 4.0 on android 2.1

Even though I have done some app on android, I am still confused. Is it possible to use functions in SDK 4.0, and run the app on android 2.1 or lower?
I tried methods you guys mentioned but got an error -
Field requires API level 11 (current min is 7): android.os.AsyncTask#THREAD_POOL_EXECUTOR, if I change min to 11, the app can't install on android 2.1, so even I can use higher API, but it still can't run on android lower version...how to fix that?
From Kzinch's advice, set TargetApi to 11, then it's working!
If you want a program that runs on both SDK4 and SDK 2.1 you have two possibilities. One is to provide alternative implementations on your code when they are needed i.e., if some function from SDK4 is not available in the SDK2.1 then you add a conditional block to your code that check the SDK version and provide code for each branch.
The other possibility is to use the Android Support Libaries in order to use the same code for both SDKs (no conditional blocks required). If you need a function provided by the SDK4 but not for the SDK2.1 you can check if that function is provided by a support library. If it is you can use it and your code will run fine on both SDK4 and SDK2.1 without requiring any version checking. For instance, if you need to use the LruCache class which is available since API level 12 (and so not available on SDK2.1) you can use the v4 support library which provide that function and works on SDK2.1 and SDK4. So in your code you would use
import android.support.v4.util.LruCache;
instead of
import android.util.LruCache;
Yes, you can use functions from the higher API in your code, but you must make sure they are never called on the lower API in runtime.
You should make checks for API level in runtime and provide alternative implementation that exists for that API level.
Let me provide some simple example:
SharedPreferences.Editor edit = PreferenceManager
.getDefaultSharedPreferences(getActivity()).edit();
edit.putInt(KEY, VALUE);
if (Build.VERSION.SDK_INT >= 9) {
edit.apply();
} else {
edit.commit();
}
apply() method is a faster (asynchronous) implementation of commit() method, but it not supported on the API level less than 9. With the help of API version check it all works perfect for all devices.
Update #TargetApi annotaion may be used to suppress Lint warnings/errors for API checks.
it doesn't matter what SDK level you compile your code against. Important is which methods/classes are you calling/instantiating.
If you use any newer classes or methods your code WILL crash running on older devices.
The suggested method to deal with it is Lazy Loading: http://android-developers.blogspot.co.uk/2010/07/how-to-have-your-cupcake-and-eat-it-too.html
and remember, I'm saying this about the SDK.
The compatibility pack is a library developed by google that you can add to any project and use the functions of the library without issues.
Furthermore, there're 3rd party libraries (such as the ActionBar Sherlock http://actionbarsherlock.com/ that aims to bring higher SDK level functionalities to lower SDK levels)
No. You cannot use methods from higher API, because the code to handle it is simply not present on lower version of API. You can, however target as high API version as possible, but you may take care to call these methods on right API. You can easily check that at runtime with. i.e.
f( Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB ) {
// code to be run on Honeycomb and higher versions
}
If you are using the API which are specific to higher version, then the app wont work in older version.As those are not defined in the older version it will throw an error.That is the reason we restrict apps before uploading into market using minSDK in AndroidManifest.xml.

Is reflection necessary if I use "if (android.os.Build.VERSION.SDK_INT>=11)"

I'm working on an app that targets API 11 (3.0) but minSDKVersion is 7 (2.1).
I generate my PreferenceActivity programmatically instead of with XML. In Honeycomb, preference layouts have a built-in spot for an icon that can go next to each preference. You can set it with prefScreen.setIcon(R.drawable.my_icon);
So I don't want to do this on API 7-10. Is this sufficient protection from crashes?
if (android.os.Build.VERSION.SDK_INT>=11)
prefScreen.setIcon(R.drawable.myIcon);
The more elaborate solution that I know is safe is to use reflection to check if that method exists before trying to use it.
According to http://developer.android.com/training/basics/activity-lifecycle/starting.html, it's implied that it's safe to use the SDK_INT constant on Android 2.0 and above to wrap calls to newer APIs, without using reflection.
Caution: Using the SDK_INT to prevent older system's from executing
new APIs works in this way on Android 2.0 (API level 5) and higher
only. Older versions will encounter a runtime exception.
This worked for me:
if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.HONEYCOMB){
//code
}
If the method is not available on a lower versions of the platform, it will crash when the file is loaded by the system (it won't even make it to execution of your if statement)
You should look at the article on Lazy Loading to do the reflection on the Android Dev Blog

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