Odex file Vs dex file

I am curious to know the differences between odex file and dex file. I searched on net but did not find enough information.Here are my questions

1. What is the purpose of odex file?
2. How can create o开发者_如何学Cdex file for my application?
3. If I create odex, will it be supported on all API levels?

Thanks, Manan

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1. It's an app optimized code
2. You can do that on the device, you'll need the command line dexopt-wrapper and running something like dexopt-wrapper
3. Yes, but you don't have to create odex files the system does that by itself. Well, depends what you want to achieve actually.

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Here's my answer for question two:

How can create odex file for my application?

The "classes.dex" file is optimized to odex file automatically. If "xxx.apk" stores in /data/app/xxx/xxx.apk, then its "xxx.odex" will be stored in /data/app/xxx/oat/arm/xxx.odex.

I tested on Android 6.0.

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Not sure how to recreate an odex file, but here's a description.

http://www.addictivetips.com/mobile/what-is-odex-and-deodex-in-android-complete-guide/