Performance optimisations for android applications - Multiple column grid gallery

Part 9 - It soon became clear that a single column gallery was not going to highlight any differences between the custom android performance optimisations or any of the other android performance third party image libraries that have been or will be reviewed.

For further info checkout - https://www.nigeapptuts.com/?p=227

Link for the grid gallery using glide - https://youtu.be/wd6buMEazBc
Link for the grid gallery using picasso - https://youtu.be/wRnHiEVGYyU

This was my motivation to covert the single column grid gallery to multiple columns so all of the screen would be occupied by thumbnail image pixels.

I will re-run this grid gallery using the picasso & glide image libraries at a later stage and provide the results in this description.

These tutorials are expected to be viewed in sequence starting from
Part 1 Picasso image library - https://youtu.be/8051fZyWToA
Part 2 Creating AsyncTask - https://youtu.be/Sj7T_oRMbd8
Part 3 BitmapFactory.Options inSampleSize - https://youtu.be/AxjTLMLYzcg
Part 4 Fixing concurrency - https://youtu.be/4qy9Yw6BmXU
Part 5 Memory cache - https://youtu.be/nOJuoodz3ts
Part 6 Reuse of bitmaps with inBitmap - https://youtu.be/p3ABIc_VAkc
Part 7 Glide image framework - https://youtu.be/oMiOj9j7VgE
Part 8 Picasso revisited - https://youtu.be/5h-6cSApJZI

In this tutorial we will cover:
- Removing the padding from the main layout xml file
- Creating members for the image dimensions & number of columns
- Using DisplayMetrics & WindowManager to get the width of the screen
- Calculating the thumbnail image width & height
- Programmatically creating the ImageView inside the recyclerview adapter using the thumbnail width & height from the main activity.
- Passing the programmatically created ImageView into the ViewHolder and using it to replace the ImageView from the xml file
- Passing the thumbnail image width & height through to the BitmapWorkerTask to be provided for bitmap in sampling.

The previous tutorials were aimed at beginners to android but over time have been getting more complex as the original camera_intent app has developed.
This tutorial series is more aimed towards the intermediate developers thought for those who have been following the previous tutorial series, feel free to watch this android performance series.

Android studio (1.3.1) is the editor of choice (IDE) for this tutorial series.

API's covered
- DisplayMetrics
- getWindowManager().getDefaultDisplay().getMetrics(DisplayMetrics)
- GridLayoutManager
- ImageView
- LinearLayout.LayoutParams

This tutorial series is the start of what I expect to be many so I encourage comments and feedback to improve the quality and viewing experience.