how to set direction of whole application to RTL?

The easiest and best way
go to the app/res/values/styles and add below code to <style> tag, that you defined its name in android manifest for example :

<style name"YourMainThemeName" parent="Parent Theme Of Your Choice">
    <item name="android:layoutDirection">rtl</item>
</style>

and now go to the app/manifests/AndroidManifest.xml and add below line code to <application> tag :

<application
        android:supportsRtl="true"
        android:theme="@style/YourMainThemeName">
</application>

now your layout directions is rtl.

Please check this text extract from android developers weblog:

To take advantage of RTL layout mirroring, simply make the following changes to your app:

1- Declare in your app manifest that your app supports RTL mirroring. Specifically, add android:supportsRtl="true" to the element in your manifest file.

2- Change all of your app's "left/right" layout properties to new "start/end" equivalents. If you are targeting your app to Android 4.2 (the app's targetSdkVersion or minSdkVersion is 17 or higher), then you should use “start” and “end” instead of “left” and “right”. For example, android:paddingLeft should become android:paddingStart.

If you want your app to work with versions earlier than Android 4.2 (the app's targetSdkVersion or minSdkVersion is 16 or less), then you should add “start” and end” in addition to “left” and “right”. For example, you’d use both android:paddingLeft and android:paddingStart.

the full text can be found here:

http://android-developers.blogspot.ca/2013/03/native-rtl-support-in-android-42.html

I had the same problem , all you need to do is just consider all your used parent container (LinearLayout , RelativeLayout , GridView , etc) and set the LayoutDirection to RTL you can approach this way programmtically thanks to ViewCompat class to include api lower than 17.

ViewCompat.setLayoutDirection(yourParentContainer,ViewCompat.LAYOUT_DIRECTION_RTL);

note that there is no need to set the Direction for childviews separately