android-training | 【Android Practice Manual】 | Android library

My Settings: minSdkVersion 19 && compileSdkVersion 30

I tried below code. I expected the button's background to be colored as colorAccent, but it was colored as colorPrimary. When I change colorPrimary value to another color, the button's background color changes accordingly.

This is contrary to what I learned. (Button's background should be colored by colorAccent when style is "@style/Widget.AppCompat.Button.Colored"). I encountered this problem while following the Google Android fundamental tutorial (https://developer.android.com/codelabs/kotlin-android-training-interactivity/index.html#4).

I am getting confused, please help.

I am trying to understand codelab 6.2 Coroutines and Room in Android Kotlin Fundamentals. Class SleepTrackerViewModel includes (with comments added by me):

I'm following the Android Code Lab for Espresso testing

It is outdated because it uses ActivityTestRule instead of the recommended ActivityScenarioRule

Outdated Code Snippets

The rule

I worked myself thru the AndroidFundamtentals Tutorial 09.2 (App Settings) but I couldn't find a working solution for my problem.

I want to change the style (backgroundcolor) of the Settings-Fragment in my app.

That's what I have coded in the styles.xml so far:

I am following the codelab https://developer.android.com/codelabs/kotlin-android-training-add-navigation/index.html#9, and I use the following code to wire up the drawer:

Except being the first Activity upon the Start of the Application, is there anything else special about main activity? From:https://developer.android.com/codelabs/android-training-create-an-activity#0

An app usually consists of multiple screens that are loosely bound to each other. Each screen is an activity. Typically, one activity in an app is specified as the "main" activity (MainActivity.java), which is presented to the user when the app is launched. The main activity can then start other activities to perform different actions.

From the quote above it seems to me that we have following hierarchy:

but then further is said:

Each time a new activity starts, the previous activity is stopped, but the system preserves the activity in a stack (the "back stack"). When a new activity starts, that new activity is pushed onto the back stack and takes user focus. The back stack follows basic "last in, first out" stack logic. When the user is done with the current activity and presses the Back button, that activity is popped from the stack and destroyed, and the previous activity resumes.

Does this also apply to the "MainActivity"? If the "MainActivity" is destroyed does that cause the App to crash i.e does the lifecycle of the MainActivity in any way differs from the lifecycle of any other activity? Is the MainActivity the last activity that is being stopped when the App is exited?

Why do I need this:

I would like to free some resources when the App is exited (in the onStop() Method (because post Honeycomb it is guaranteed that onStop will be called)), especially ExecutorServices, I've read here that even though App is exited there is no guarantee that an ExecutorService will be stopped and will make JVM continue working/running, even though App is closed/killed and will continue to use system resources.

I have a simple setup of 2 fragments: ConversationFragment and DetailsFragment

I am using Room with Paging 3 library and to populate the ConversationFragment I am using a PagingLiveData implementation together with a AndroidViewModel belonging to the ConversationFragment.

I am not using the Navigation Components here, just a common fragment navigation as per Android documentation.

From that fragment I can open the DetailsFragment and then return back to the fragment again. Everything is working well, until I open said fragment and return, then the observer that was tied in the ConversationFragment is lost since that fragment is being destroyed when opening the DetailsFragment.

So far this is not a big issue, I can restart the observer again and it does work when I do that. However, when I attach the observer again the entire list reflows, this causes the items in the RecyclerView to go wild, the position the list was on is lost and the scrollbar changes sizes which confirms pages are being loaded/reloaded.

I could withstand the weird behavior to a degree, but to have the position lost on top of that is not acceptable.

I looked into caching the results in the view model, but the examples I could find in the available documentation are basic and do not show how the same could be achieved using a LiveData<...> object.

Currently this is what I have:

ConversationFragment

I used this CodeLabs tutorial to learn how to make an HTTP request from the Google Books API https://codelabs.developers.google.com/codelabs/kotlin-android-training-internet-data/#4

Right now, I'm trying to access a nested JSON object that the Google Books API spits out I.e

I have just started my first Kotlin app, and I'm aiming to learn the best practices for that language along the way (and end up with a working app of course :) ). I've come across a problem I find myself struggling with for some time: What should be the flow of an onClick event?

At first, I used the strait forward way of setting the onClick in my fragment like so: binding.image_profile_picture.setOnClickListener { onChangePhoto() }.

I went over some of the kotlin training codelabs and changed my code accordingly. One thing I understood is that it is recommended to handle events in the ViewModel and not in the fragment (codelab#3), so now my onClicks are set in the layout xml like so: android:onClick="@{() -> profileViewModel.onChangePhoto()}".

The problem with that is all of my events actually need a context as they start with some kind of dialog (like the image picker). I found this article recommending to solve this problem using an event wrapper. I read the discussion on it's implementation's Github page and decided to give it a shot (also I'm not sure I like this unnecessary ViewModel-Fragment ping-pong). I implemented aminography's OneTimeEvent and now my ViewModel looks like this: