Develop Reference

Using material design, how to programmatically create a Material Button?

I know how to create a normal button and textview programmtically. However, the documentation for Material design components is a bit lacking. How would I dynamically create a Material Button (and other Material Design components)?
Was referring to the official documentation here but it only shows xml creation. Seems like it should be fairly straightforward but I haven't found anything on google / stackoverflow covering this.

You need to add proper dependency. Check this link Then you can create it as average view.

How can I have a tabbed app in Android like Spotify does?

I'm totally new to Android development. I even don't know the name of components yet, something that make a bit harder to find how can I reach my goals.
Now my main goal is to desing a screen with a bottom tabbed bar, where the user can click in the tabs and the body of the screen changes, like the Spotify's do.
This image shows exactly what I'm looking for with those five icons at the bottom.

You are looking for navigation bottom bar.
Link for design guidelines:
https://material.io/guidelines/components/bottom-navigation.html
Link for example library implementation: https://github.com/aurelhubert/ahbottomnavigation

Android - How to implement Google Newsstand like layout?

I'm trying to clone the “view article" fragment layout of Google Newsstand app. It has an ImageView on the top that shrinks to become a Toolbar when we scroll downwards, just below the ImageView lies a TextView that contains the text content of the article. While creating the layout itself is pretty easy, implementing the special kind of scroll effect that shrinks the ImageView into a Toolbar is pretty tricky. Since, most of the updated Google Apps containing material design(e.g. - Play Store, Google+, etc.) contains similar kind of layouts, I was wondering if there's any widget/custom library available for the same. If so, what is it called and how to implement it?
Here's what the layout looks like:

You can use libraries like NotBoringActionBar or Header2ActionBar, but, as the babe says, they're Action Bars and in Lollipop they are deprecated.
Anyways, you can find them on GitHub.

This is called the 'Flexible Space with Image' pattern. It is a popular scrolling technique. The new Android Design Support Library enables you to implement this with ease. This post should help you make it.

Material Design Buttons and other components

Im trying to make an application Lollipop & Material Design compatible following the latest guidelines.
Anyhow I'm having troubles finding the appropriate documentation for the components for Lollipop on developer.android.com it kinda seems like the documentation is stuck with KitKat and appropriate documentation is missing.
I have the need to implement Flat Buttons like these (http://www.google.com/design/spec/components/buttons.html#buttons-flat-raised-buttons) and Icon Toggles like these (http://www.google.com/design/spec/components/buttons.html#buttons-other-buttons).
Besides that I'm also trying to implement big style App Bar/Toolbar - again can't find an appropriate documentation.
Any tips?

for the new tool bar api have a look at http://developer.android.com/reference/android/widget/Toolbar.html
http://android-developers.blogspot.co.il/2014/10/appcompat-v21-material-design-for-pre.html
for button styles you just need to use elevation
https://developer.android.com/training/material/shadows-clipping.html
for buttons togglers just use selectors / ripple effect
https://developer.android.com/reference/android/graphics/drawable/RippleDrawable.html
gl

Well it depends on what you are looking for and want to achieve for the material design look and feel.
The url's you have are more the design guidelines. About how everything should look. It's as important as the developers guidelines if you design too.
Material Activity transitions
But when you think about the material design transitions where they don't want those static transitions like "Go from this activity to another" But more like a dynamic transition you can look for examples and explanation here: https://developer.android.com/training/material/animations.html
Ripples
If you want to know more about the touchy ripple effects and things like how to get the 'hairline' color of components you can find more here: http://android-developers.blogspot.nl/2014/10/implementing-material-design-in-your.html
Elevation
Also Material design wants you to play more with the elevation of elements. Check that here: https://developer.android.com/training/material/shadows-clipping.html
And ofcourse there is more. Look in the left menu where you can find more best practice examples. Also the new Android 21.+ SDK offers new examples released a couple of weeks ago. Check those out to see how google implements Material design for api level 21.+

Styling the "Share" action menu

I'm trying to add a "Share button" to my app, but I haven't found a way to manage the styling of the ActionMenu displayed to choose the app to share content to.
Currently it appears as in this screenshot:
However, I'd like to change the background color and the text color to make them reflect the ones in the ActionBar: which are the style properties that handle these two colors?

I would suggest follow this tutorial and using the linked tool:
http://blog.stylingandroid.com/styling-the-actionbar-part-3/
Jeff Gilfelt Android Action Bar Style Geberator tool
Quick mockup below, to prove it's very relevant and helpful in the direction of solving your question: