android-room-with-a-view | May 2017 Google released the Architecture Components | Architecture library

I am now learing how to save data in a local database using Room in Android Dev Doc. And I had done the Codelab in this links.https://developer.android.com/codelabs/android-room-with-a-view#0 I can Upddate, Insert, Delete and Query all data in table. Now, I want Query the data with specific id. How should I code in ViewModel and Repository class? Thanks. My table named "Diary", Diary.class

I'm looking through the tutorial for Android room with a view, and trying to extend their model for using ViewModels to multiple fragments, but not really sure how.

MyApplication

I have just followed this guide: https://developer.android.com/codelabs/android-room-with-a-view#12

(not only page 12 but all from 1 to 17).

On that link it shows the following code:

I have stepped through the Android Room with a View - Java codelab and wound up with an error that causes the app to crash before it loads (see "fatal exception", below). Thinking perhaps I did something wrong, I copied the contents of each of the .java solution files from github.

I tried creating overloading the WordViewModel class with another constructor that took no arguments, but that only created more issues.

I was working with one of the codelabs tutorials https://codelabs.developers.google.com/codelabs/android-room-with-a-view/index.html?index=..%2F..index#3 . Int which while editing buil.gradle (app) . I got Failed to resolve : androidx ,Failed to resolve : androidx.arch & Failed to resolve : com.google.android

build.gradle

I'm trying to make a simple ToDoList application using the recyclerview and the room library. I'm following the android developers codelab on using room and mvvm architecture and I seem to have hit a stump. I have set up every layer of the application but I'm getting an error when trying to instantiate the ViewModel using the ViewModelProvider. Here is the code from my ViewModel class.

I have read the artical.

When you are initialising the ViewModel through ViewModelProviders without a factory, this means that you can only instantiate a ViewModel which has no constructor arguments.

The following code is from the project android-room-with-a-view

Why can the project create an instance of class ViewModel with constructor argument without a factory in Kotlin?

Code

In my MainActivity, I have items displayed in an Adapter. These items are Room Entity objects. When I click an item in the Adapter I start a DetailActivity.

Now in this DetailActivity, I'd like to get the clicked item using a ViewModel and the Entity object's ID.

My problem is, I'm not sure how to do this. Should I use LiveData? I'm confused because examples like this Google Codelab always wrap Entity objects in LiveData, so to get the object itself you have to observe changes with onChanged and use the method's parameter.

My current approach is to use Intent putExtra in MainActivity to send the item's ID to DetailActivity:

I have followed the Android Room with a View tutorial but have changed it to a single-activity app with multiple fragments. I have a fragment for inserting records. The save button calls the viewmodel save method and then pops the backstack to return to the previous (list) fragment. Sometimes this works but often the insert does not occur. I assume that this is because once the fragment is destroyed, the ViewModelScope cancels any pending operations so if the insert has not already occured, it is lost.

Fragment: