Added Android SDK validation (>= 21)

[mrnkr]

Hey!

So, as the title says, I added the validation for the Android SDK to have the setElevation method available and added a quick heads up to whoever reads the README that shadows are not shown on any version of Android older than Lollipop.

Since design didn't rely that much on shadows back then (as far as I can remember...) don't think it's a big deal, if it were I guess I could look for an alternative implementation that's compatible.

I tested my changes on Android 4.4 and made sure no unexpected behaviors were found by testing on Android 8.1 and iOS 11.2.

Hope you find this useful!

[berardo]

Thanks for looking into that, Alvaro

[mrnkr]

Hey there!

Saw you changed my code a little bit when you moved it... Although your version looks better it has a problem...
Running this code:

android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.LOLLIPOP

on a phone that is running Android 4.4 results in the following exception:

JS: ERROR Error: java.lang.NoSuchFieldError: no static field with name='LOLLIPOP' signature='I' in class Landroid/os/Build$VERSION_CODES;
JS:     com.tns.Runtime.callJSMethodNative(Native Method)
JS:     com.tns.Runtime.dispatchCallJSMethodNative(Runtime.java:1088)
JS:     com.tns.Runtime.callJSMethodImpl(Runtime.java:970)
JS:     com.tns.Runtime.callJSMethod(Runtime.java:957)
JS:     com.tns.Runtime.callJSMethod(Runtime.java:941)
JS:     com.tns.Runtime.callJSMethod(Runtime.java:933)
JS:     com.tns.gen.org.nativescript.widgets.Async_CompleteCallback.onComplete(Async_CompleteCallback.java:12)
JS:     org.nativescript.widgets.Async$Http$HttpRequestTask.onPostExecute(Async.java:585)
JS:     org.nativescript.widgets.Async$Http$1$1.run(Async.java:486)
JS:     android.os.Handler.handleCallback(Handler.java:733)
JS:     android.os.Handler.dispatchMessage(Handler.java:95)
JS:     android.os.Looper.loop(Looper.java:136)
JS:     android.app.ActivityThread.main(ActivityThread.java:5584)
JS:     java.lang.reflect.Method.invokeNative(Native Method)
JS:     java.lang.reflect.Method.invoke(Method.java:515)
JS:     com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1268)
JS:     com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1084)
JS:     dalvik.system.NativeStart.main(Native Method)

For that, instead of using android.os.Build.VERSION_CODES.LOLLIPOP it is better to use just the value it returns (21).

The second I can I'll submit a PR with a quick fix unless you beat me to it!
Have a good one!

[berardo]

Oh sorry for that.
6e37455 should fix that.
I'm not able to test it though, would you mind checking that for me so I can bump the version?

Thanks a lot

[mrnkr]

Just checked 6e37455 and it is perfect, no issues :)