Develop Reference

How to implement system bars insets with edge-to-edge gesture navigation?

I'm trying to add the edge-to-edge stuff for the gesture navigation bar to the Tip Time app from Google. I added the transparent navigationBarColor XML tag to themes.xml as well as the following code to the onCreate() function of MainActivity.kt:
This was directly copy-pasted from the documentation. Android Studio says that "it cannot find a parameter with this name" for each of the three margins. I noticed that changing the parenthesis right after <ViewGroup.MarginLayoutParams> to curly braces fixes the compiler error. Maybe the documentation is just wrong?
Anyways, even after fixing that, the app still doesn't look right:
As you can see, the entire view gets shifted up slightly and the "Cost of Service" TextView is partially cut-off by the app bar. What would I need to change to implement the system/navigation bar insets for edge-to-edge content so the UI looks nice? Also, as a side-question, how can I change the dark blue color of the system status bar to match the color of the app bar so that they look blended?

As per documentation for edge to edge contents:
Draw behind the status bar if it makes sense for your content and
layout, such as in the case of full-width imagery. To do this, use
APIs such as AppBarLayout, which defines an app bar pinned to the top
of the screen.
So, while handing the window insets (especially the top one), you can't use the default ActionBar, instead you need to customize that with AppBarLayout and ToolBar, and to make it act as the ActionBar, use setSupportActionBar(), and a NoActionBar app theme; it'd be <style name="Theme.TipTime" parent="Theme.MaterialComponents.DayNight.NoActionBar"> in the shared repo.
the entire view gets shifted up slightly and the "Cost of Service" text field is partially cut-off by the app bar.
The reason that the sample uses the default ActionBar instead of a customized one; when it comes to handle the top window insets, it won't affect the default ActionBar; notice that you pass in the activity's root layout to setOnApplyWindowInsetsListener callback, and as the ActionBar is not a part of the activity, it won't be affected. Therefore the activity is shifted up behind the ActionBar when the top inset is removed. So, to solve this you have either to totally remove the default ActionBar or to use a custom toolbar instead.
Also, as a side-question, how can I change the dark blue color of the system status bar to match the color of the app bar so that they look blended?
Use a transparent status bar color in the app's theme:
<item name="android:statusBarColor" tools:targetApi="l">#android:color/transparent</item>

What would be a good way to show activity title without actionbar?

Im making an app for android, without actionbar.
What is best practice for showing titles without actionbar?

The best practice is basically never using an action bar. This gives you a complete device screen to play with.
You can use images or different text styles for showing the title. You can also use interesting icons.
To remove action bar -
Go to res > values > styles.xml
Here is an illustration of styles file -

You can use the Toolbar (it's like the action bar, but more flexible). For example, action bar needs to be on top of the screen, but toolbar can have place anywhere in the layout.
You title can be shown as text or a beautiful asset.
If, for some reason, you don't want to use the toolbar, you can think about something like having a scrollView with the title on top of it.

Use a regular LinearLayout with a TextView inside. Style according to your needs, and set the text in the xml, or programmaticaly using TextView's setText() method.

ConstraintLayout in Android Studio - overlapping title bar, but title bar doesn't appear in design view or XML

So, if you build an app in Android Studio, you can of course use ConstraintLayout. I set the constraints, but often find that when I actually launch the app, the content is under the title bar at the top. But the title bar isn't apparently something you can access while designing (either in Design or Text view of the layout).
Is there a good way of avoiding this? Making sure that you don't overlap the title bar on devices?

Yes, use fitSystemWindows flag or xml property in main view.

Custom title bar vs. layout with header

I recently thought of adding a custom title bar to my app (with "find me" and home button and such) and then I thought what is the reason of using a custom title bar at top instead of just a normal layout and using it as an include tag at the top of my XML's
What are the pros and cons of each? Is there realy a difference?
EDIT: one difference ive found so far is that the custom title bar has a shadows automaticly

For having back and home button titlebar, you should define normal layout for the same. Because it is easy to implement as compared to customized the native title bar. And we can create normal layout as we wants with any color/height/width/image backround/etc.
I suggest you to go with defining normal layout for the title bar instead of customizing the native title bar.

You can extend LinearLayout to create a new layout with your title bar. The advantage is you can then customise the title bar for different activities that use it. Some may not want to display the find button for instance.
If you use include in XML you don't have the same flexibility.
I would create a custom layout with the title bar.

Spinner pop up window title background

I would like to modify the background of the title bar of the dropdown dialog associated to a spinner.
If this is not possible I would like to know what resource is used to draw this background android.R.drawable.* ?
This is an effort of uniformity for my various pop ups in my application.

You can change everything using styles and themes.
Take a look at this example for buttons:
http://blog.androgames.net/40/custom-button-style-and-theme/