In my Android app i have multiple intent services which run one after another and the very first intent service is trigerred by a broadcast. I came across [Work Manager][1] a few days ago and really liked the simplicity of the Worker and the WorkManager classes. What are the pros and cons of Work Manager over regular intent services? Should i switch to work manager now considering the fact that i may have to write more intent services in the future? Also which option would help me test the code easily?


  [1]: https://developer.android.com/reference/androidx/work/WorkManager

Android Work Manager vs Services?

I&#39;m using Android Studio 3.2 Canary 14 and [The Navigation Architecture Component][1]. With this you can define transition animations pretty much as you would when using Intents. 

But the animations are set as properties of the actions in the navigation graph, like so:

    &lt;fragment
        android:id=&quot;@+id/startScreenFragment&quot;
        android:name=&quot;com.example.startScreen.StartScreenFragment&quot;
        android:label=&quot;fragment_start_screen&quot;
        tools:layout=&quot;@layout/fragment_start_screen&quot; &gt;
      &lt;action
        android:id=&quot;@+id/action_startScreenFragment_to_findAddressFragment&quot;
        app:destination=&quot;@id/findAddressFragment&quot;
        app:enterAnim=&quot;@animator/slide_in_right&quot;
        app:exitAnim=&quot;@animator/slide_out_left&quot;
        app:popEnterAnim=&quot;@animator/slide_in_left&quot;
        app:popExitAnim=&quot;@animator/slide_out_right&quot;/&gt;
    &lt;/fragment&gt;

This gets tedious to define for all actions in the graph!

**Is there a way to define a set of animations as default, on actions?** 

I&#39;ve had no luck using styles for this.


  [1]: https://developer.android.com/topic/libraries/architecture/navigation/

How do I define default animations for Navigation Actions?

I&#39;m new to the Android Jetpack Navigation architecture. I&#39;m trying it out on a new app. There&#39;s one activity and a few fragments, two of them are login screen and email login screen. I defined those fragments in my navigations XML. The flow of the app is as follows:

```Login screen``` → ```Email Login screen```

What I want is, after navigating to the email login screen, when I press back, the app exits. Meaning the back-stack for login screen is removed. I know login screens aren&#39;t supposed to work that way, but I&#39;m still just figuring things out.

I followed the documentation from Google&#39;s [Get started with the Navigation component](https://developer.android.com/guide/navigation/navigation-getting-started). It said, using ```app:popUpTo``` and ```app:popUpToInclusive=&quot;true&quot;``` is supposed to clear the backstack, yet when I press back on email login screen, it still goes back to login instead of exiting.

So, here&#39;s what I&#39;ve tried.

nav_main.xml
```
&lt;fragment android:id=&quot;@+id/loginFragment&quot;
          android:name=&quot;com.example.myapp.ui.main.LoginFragment&quot;
          android:label=&quot;@string/login&quot;
          tools:layout=&quot;@layout/fragment_login&quot; &gt;
	
	&lt;action
		android:id=&quot;@+id/action_login_to_emailLoginFragment&quot;
		app:destination=&quot;@id/emailLoginFragment&quot;
		app:popEnterAnim=&quot;@anim/slide_in_right&quot;
		app:popExitAnim=&quot;@anim/slide_out_right&quot;
		app:popUpTo=&quot;@+id/emailLoginFragment&quot;
		app:popUpToInclusive=&quot;true&quot;/&gt;

&lt;/fragment&gt;

&lt;fragment android:id=&quot;@+id/emailLoginFragment&quot;
          android:name=&quot;com.example.myapp.ui.main.EmailLoginFragment&quot;
          android:label=&quot;EmailLoginFragment&quot;
          tools:layout=&quot;@layout/fragment_login_email&quot; /&gt;
```


LoginFragment.kt
```
override fun onCreateView(
	inflater: LayoutInflater, container: ViewGroup?,
	savedInstanceState: Bundle?
): View {
	binding.emailLoginButton.setOnClickListener {
		findNavController().navigate(R.id.action_login_to_emailLoginFragment)
	}
	
	return binding.root
}
```

I gave a click event to a button. In it, I used the Navigation Controller to navigate to the email login screen by giving it the action&#39;s ID. In the ```&lt;action&gt;```, there are ```app:popUpTo``` and ```app:popUpToInclusive=&quot;true&quot;```.

After reading the documentation over and over, as well as reading plenty of StackOverflow questions, I found those properties are supposed to remove my login screen off the back-stack. But they don&#39;t. The button does navigate to the email login screen, but when I press back, it still goes back to login screen instead of exiting the app. What am I missing?

Navigation popUpTo and PopUpToInclusive aren&#39;t clearing the backstack

I want to initialize ViewModel in Activity using androidx library

I have tried what documentation says but it is not working. the &quot;.of&quot; is not resolved.
 

```kotlin
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import androidx.databinding.DataBindingUtil
import androidx.lifecycle.ViewModelProvider
import com.example.myapplication.databinding.ActivityMainBinding`

class MainActivity : AppCompatActivity() {

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        val binding: ActivityMainBinding = DataBindingUtil.setContentView(
            this, R.layout.activity_main)
        binding.setLifecycleOwner(this)

        var model = ViewModelProvider.of(this).get(SheduleViewModel::class.java)

    }
}
```



of is not resolved, maybe there are another way to do it in androidx



how to instantiate ViewModel In AndroidX?

I am reading about a room library of Android. I see they changed package `android` to `androidx`. I did not understand that. Can someone explain, please?

    implementation &quot;androidx.room:room-runtime:$room_version&quot;
    annotationProcessor &quot;androidx.room:room-compiler:$room_version&quot;

Even this is available with the `android` package also.

    implementation &quot;android.arch.persistence.room:runtime:$room_version&quot;
    annotationProcessor &quot;android.arch.persistence.room:compiler:$room_version&quot;


 - What was in need of packaging new support libraries in `androidx` instead of `android`?
 - Use case and affect factors in existing projects.


What is AndroidX?

I&#39;m trying to use the new Android P FloatingActionButton that&#39;s part of the `com.google.android.material.floatingactionbutton.FloatingActionButton` and I&#39;m getting this warning:

&gt; VisibilityAwareImageButton.setVisibility can only be called from the same library group (groupId=com.google.android.material)


    import com.google.android.material.floatingactionbutton.FloatingActionButton
    import android.view.View

    class MainActivity : AppCompatActivity() {

        lateinit var demoFab: FloatingActionButton
    
        override fun onCreate(savedInstanceState: Bundle?) {
            demoFab = findViewById(R.id.demoFab)
            demoFab.visibility = View.VISIBLE  // the warning is here
        }
    }

[![enter image description here][1]][1]


I&#39;ve tried searching and the only search result is in regards to responding to UI visibility changes:

[Respond to UI visibility changes](https://developer.android.com/training/system-ui/visibility)

I tried exploring how I could to see if there was a `VISIBLE` int value in that `com.google.android.material` package and the only one I found was `com.google.android.material.floatingactionbutton.FloatingActionButton.VISIBLE`, but the warning still remains.

  [1]: https://i.stack.imgur.com/MH3mw.png

## Top-level build.gradle

    buildscript {
        ext.kotlin_version = &#39;1.2.41&#39;
        repositories {
            google()
            jcenter()
        }
        dependencies {
            classpath &#39;com.android.tools.build:gradle:3.2.0-alpha14&#39;
            classpath &quot;org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version&quot;
            classpath &quot;com.google.gms:oss-licenses:0.9.2&quot;
            // NOTE: Do not place your application dependencies here; they belong
            // in the individual module build.gradle files
        }
    }
    
    allprojects {
        repositories {
            google()
            jcenter()
            mavenCentral()
            maven { url &quot;http://oss.sonatype.org/content/repositories/snapshots/&quot; }
        }
    }
    
    task clean(type: Delete) {
        delete rootProject.buildDir
    }


## Project-level build.gradle

    apply plugin: &#39;com.android.application&#39;
    
    apply plugin: &#39;kotlin-android&#39;
    
    apply plugin: &#39;kotlin-android-extensions&#39;
    
    apply plugin: &#39;com.google.gms.oss.licenses.plugin&#39;
    
    android {
        compileSdkVersion &#39;android-P&#39;
        defaultConfig {
            applicationId &quot;com.codeforsanjose.maps.pacmap&quot;
            minSdkVersion 21
            targetSdkVersion &#39;P&#39;
            versionCode 1
            versionName &quot;1.0&quot;
            testInstrumentationRunner &quot;androidx.test.runner.AndroidJUnitRunner&quot;
        }
        splits {
            abi {
                enable true
                reset()
                include &#39;arm64-v8a&#39;, &#39;armeabi&#39;, &#39;armeabi-v7a&#39;, &#39;mips&#39;, &#39;x86&#39;, &#39;x86_64&#39;
                universalApk false
            }
        }
        compileOptions {
            sourceCompatibility JavaVersion.VERSION_1_8
            targetCompatibility JavaVersion.VERSION_1_8
        }
        buildTypes {
            release {
                minifyEnabled true
                shrinkResources true
                proguardFiles getDefaultProguardFile(&#39;proguard-android.txt&#39;), &#39;proguard-rules.pro&#39;
            }
        }
    }
    
    dependencies {
        implementation fileTree(dir: &#39;libs&#39;, include: [&#39;*.jar&#39;])
        implementation &quot;org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version&quot;
        implementation &#39;androidx.appcompat:appcompat:1.0.0-alpha1&#39;
        implementation &#39;androidx.constraintlayout:constraintlayout:1.1.0&#39;
        testImplementation &#39;junit:junit:4.12&#39;
        androidTestImplementation &#39;androidx.test:runner:1.1.0-alpha2&#39;
        androidTestImplementation &#39;androidx.test.espresso:espresso-core:3.1.0-alpha2&#39;
    
        implementation &#39;com.mapbox.mapboxsdk:mapbox-android-sdk:5.5.2&#39;
        //implementation &#39;com.mapbox.mapboxsdk:mapbox-android-sdk:6.1.0&#39;
        implementation &#39;com.mapbox.mapboxsdk:mapbox-android-plugin-locationlayer:0.5.0&#39;
        implementation &#39;com.mapbox.mapboxsdk:mapbox-android-navigation:0.13.0&#39;
        implementation &#39;com.mapbox.mapboxsdk:mapbox-android-navigation-ui:0.13.0&#39;
    
        implementation &#39;com.google.android.gms:play-services-oss-licenses:15.0.1&#39;
        implementation &#39;com.google.code.gson:gson:2.8.2&#39;
        implementation &#39;com.squareup.moshi:moshi:1.5.0&#39;
        implementation &#39;com.squareup.okhttp3:logging-interceptor:3.10.0&#39;
        implementation &#39;com.squareup.retrofit2:converter-gson:2.3.0&#39;
        implementation &#39;com.squareup.retrofit2:converter-moshi:2.4.0&#39;
        implementation &quot;com.squareup.retrofit2:adapter-rxjava2:2.3.0&quot;
        implementation &#39;com.squareup.retrofit2:retrofit:2.4.0&#39;
        implementation &#39;io.reactivex.rxjava2:rxandroid:2.0.1&#39;
        implementation &#39;io.reactivex.rxjava2:rxkotlin:2.2.0&#39;
    }
    

### edit:

I should note that I&#39;m using Android Studio version 3.2 canary 14. It seems there have been some reported bugs for this version, and I suspect this is one of them.


## edit 2:

Issue still exists with Android Studio version 3.2 canary 15, but I found a workaround for it using `show()` and `hide()`

    override fun onCreate(savedInstanceState: Bundle?) {
        demoFab = findViewById(R.id.demoFab)
        demoFab.show()    // this works and doesn&#39;t have the warning
    }

Android P visibilityawareimagebutton.setVisibility can only be called from the same library group

Before trying the Navigation component I used to manually do fragment transactions and used the fragment tag in order to fetch the current fragment.

`val fragment:MyFragment = supportFragmentManager.findFragmentByTag(tag):MyFragment`

Now in my main activity layout I have something like:

    &lt;fragment
            android:layout_width=&quot;match_parent&quot;
            android:layout_height=&quot;match_parent&quot;
            android:id=&quot;@+id/nav_host&quot;
            app:navGraph= &quot;@navigation/nav_item&quot;
            android:name=&quot;androidx.navigation.fragment.NavHostFragment&quot;
            app:defaultNavHost= &quot;true&quot;
            /&gt;

How can I retrieve the current displayed fragment by the Navigation component? 
Doing 

`supportFragmentManager.findFragmentById(R.id.nav_host)`

returns a `NavHostFragment` and I want to retrieve my shown &#39;MyFragment`.

Thank you.

Android Navigation Architecture Component - Get current visible fragment

I&#39;d like to know how properly handle system back button action using Navigation Controller. In my app I have two fragments (for ex. fragment1 and fragment2) and I have an action in fragment1 with destination to fragment2. Everything works well except one thing - when user presses system back button in fragment2 I want to show a dialog (using DialogFragment for example) to confirm exit. What is the best way to implement this behavior? If I use `app:defaultNavHost=&quot;true&quot;` in my host fragment then it automatically goes back ignoring my rules. And, additionally, what is this component for?

 [![enter image description here][1]][1]

Should I use &quot;pop to&quot; may be?


  [1]: https://i.stack.imgur.com/NjZ75.png

Handling back button in Android Navigation Component

I use navigation library and safeargs for passing data. I define argument to fragment like that.

    &lt;fragment
            android:id=&quot;@+id/otherFragment&quot;
            android:name=&quot;com.asd.navigate.OtherFragment&quot;
            android:label=&quot;OtherFragment&quot;&gt;
            &lt;argument
                android:name=&quot;screenTitle&quot;
                android:defaultValue=&quot;0&quot;
                app:type=&quot;string&quot; /&gt;
        &lt;/fragment&gt;

OtherFragmentArgs generated, I can use it but OtherFragmentDirection class doesnt generate when I click &quot;make project&quot;. Is that bug or I have to do something different.

Thnx for advice.


    buildscript {
        ...
        dependencies {
           ...
            classpath &quot;android.arch.navigation:navigation-safe-args-gradle-plugin:1.0.0-alpha01&quot;
    
        }
    }

build.gradle

    apply plugin: &quot;androidx.navigation.safeargs&quot;

MainActivity.kt

[![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/YfaZt.png

Safeargs library doesnt generate direction class

I&#39;m trying to implement [Navigation with Jetpack&#39;s architecture components][1] in my existing app.

I have a single activity app where the main fragment (`ListFragment`) is a list of items. Currently, when the user taps on a list item a second fragment is added to the stack by `fragmentTransaction.add(R.id.main, detailFragment)`. So when back is pressed the `DetailFragment` is detached and the `ListFragment` is shown again.

With Navigation architecture this is handled automatically. Instead of adding the new fragment it&#39;s [replaced][2], so the fragment view is destroyed, `onDestroyView()` is called and `onCreateView()` is called when back is pressed to recreate the view.

I understand that this is a good pattern used with [LiveData][3] and [ViewModel][4] to avoid using more memory than necessary, but in my case this is annoying because the list has a complex layout and inflating it is time and CPU consuming, also because I&#39;ll need to save the scroll position of the list and scroll again to the same position user left the fragment. It&#39;s possible but seems it should exists a better way.

I&#39;ve tried to &quot;save&quot; the view in a private field on fragment and re-use it on `onCreateView()` if is already there, but it seems an anti-pattern.

    private View view = null;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

        if (view == null) {
            view = inflater.inflate(R.layout.fragment_list, container, false);
            //...
        }

        return view;
    }

Is there any other, more elegant, way to avoid re-inflating the layout?
  [1]: https://developer.android.com/topic/libraries/architecture/navigation/navigation-implementing
  [2]: https://issuetracker.google.com/issues/109856764
  [3]: https://developer.android.com/topic/libraries/architecture/livedata
  [4]: https://developer.android.com/reference/android/arch/lifecycle/ViewModel

Fragments destroyed / recreated with Jetpack&#39;s Android Navigation components

I know, [androidx and support dependency causing multidex error][1]
We can not use androidx and android support at a same time. So I totally migrate to androidx. but one of my dependency lib used android support &quot;lottie&quot;.

What can we do in above situation? Should I remove &#39;lottie&#39; from my project.

below is my gradle

 

    defaultConfig {
            minSdkVersion 19
            targetSdkVersion 28
            versionCode 1
            versionName &quot;1.0&quot;
            testInstrumentationRunner &quot;android.support.test.runner.AndroidJUnitRunner&quot;
            vectorDrawables.useSupportLibrary = true
            multiDexEnabled true
        }

        ext{
        lottieVersion = &quot;2.5.4&quot;
    }
    

    dependencies {
        implementation fileTree(dir: &#39;libs&#39;, include: [&#39;*.jar&#39;])
        implementation &quot;org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version&quot;
    
        def androidx = &quot;1.0.0-rc01&quot;
        api &quot;androidx.constraintlayout:constraintlayout:1.1.2&quot;
        api &quot;androidx.appcompat:appcompat:$androidx&quot;
        api &quot;androidx.recyclerview:recyclerview:$androidx&quot;
        api &quot;androidx.cardview:cardview:$androidx&quot;
        api &quot;androidx.core:core-ktx:$androidx&quot;
        api &quot;com.google.android.material:material:1.0.0-rc01&quot;
        implementation &quot;com.google.code.gson:gson:2.8.5&quot;
        implementation &quot;androidx.multidex:multidex:2.0.0&quot;
        implementation &quot;com.airbnb.android:lottie:$lottieVersion&quot;
        }

  [1]: https://stackoverflow.com/questions/50387207/error-while-merging-dex-program-type-already-present-android-support-v4-os-resu



Can I use library that used android support with Androidx projects.

I am working with Single viewModel for the Activity and all of it&#39;s fragment.

So to initialise `viewmodel` if have to write this setup code in `onActivityCreated` of all the fragment&#39;s

        override fun onActivityCreated(savedInstanceState: Bundle?) {
            super.onActivityCreated(savedInstanceState)
            viewModel = ViewModelProviders.of(activity!!).get(NoteViewModel::class.java)
        }

I was going thorough the Android KTX extension page:([refer here][1]) 

and i found i can initialise view model like this:

        // Get a reference to the ViewModel scoped to this Fragment
        val viewModel by viewModels&lt;MyViewModel&gt;()
    
        // Get a reference to the ViewModel scoped to its Activity
        val viewModel by activityViewModels&lt;MyViewModel&gt;()

So I added below dependency&#39;s to my gradle(app):

        //ktx android
        implementation &#39;androidx.core:core-ktx:1.0.2&#39;
        implementation &#39;androidx.fragment:fragment-ktx:1.0.0&#39;
        implementation &quot;androidx.lifecycle:lifecycle-extensions:2.0.0&quot;

But when i try to use `viewModels/activityViewModels` in my application their reference in not found.
  
I want help in how to use these extension&#39;s with some basic example i tried searching for examples haven&#39;t found any.

  [1]: https://developer.android.com/kotlin/ktx#fragment

how to get viewModel by viewModels? (fragment-ktx)

We are using [DataBinding][1] since Jetpack release. Android documentation indicates that [ViewBinding][2] was added in **Android Studio 3.6 Canary 11+.**

I read the documentation but its looks similar to **DataBinding.**

Can anyone explain what&#39;s the difference between these two concepts?


  [1]: https://developer.android.com/topic/libraries/data-binding
  [2]: https://developer.android.com/topic/libraries/view-binding

Android : Difference between DataBinding and ViewBinding

I&#39;m trying to get a value from LiveData with observeAsState in jetpack compose, but I get a weird error

&gt; Type &#39;State&lt;List&lt;User&gt;?&gt;&#39; has no method &#39;getValue(Nothing?,
&gt; KProperty&lt;*&gt;)&#39; and thus it cannot serve as a delegate

Code
----

    @Composable
    fun UserScreen(userViewModel:UserViewModel){
        val items: List&lt;User&gt; by userViewModel.fetchUserList.observeAsState()
        UserList(userList = items)
    }

[![enter image description here][1]][1]

ViewModel
---------

    class UserViewModel: ViewModel() {
    
        private val dataSource = UserDataSource()
        val fetchUserList = liveData {
            emit(dataSource.dummyUserList)
        }
    }

  [1]: https://i.stack.imgur.com/xhSRG.png

Type &#39;State&lt;List&lt;User&gt;?&gt;&#39; has no method &#39;getValue(Nothing?, KProperty&lt;*&gt;)&#39; and thus it cannot serve as a delegate

*Edit:* This question is a bit out of date now that Google has given us the ability to scope `ViewModel` to navigation graphs. The better approach (rather than trying to clear activity-scoped models) would be to create specific navigation graphs for the right amount of screens, and scope to those.

--------------------------

With reference to the `android.arch.lifecycle.ViewModel` class.

`ViewModel` is scoped to the lifecycle of the UI component it relates to, so in a `Fragment`-based app, that will be the fragment lifecycle. This is a good thing.

--------------------------

In some cases one wants to share a `ViewModel` instance between multiple fragments. Specifically I am interested in the case where *many screens relate to the same underlying data*. 

(The docs suggest similar approach when multiple related fragments are displayed on the same screen but [this can be worked around by using a single host fragment as per answer below][1].)

This is discussed in the [official ViewModel documentation][2]:

&gt; ViewModels can also be used as a communication layer between different
&gt; Fragments of an Activity. Each Fragment can acquire the ViewModel
&gt; using the same key via their Activity. This allows communication
&gt; between Fragments in a de-coupled fashion such that they never need to
&gt; talk to the other Fragment directly.

In other words, to share information between fragments that represent different screens, the `ViewModel` should be scoped to the `Activity` lifecycle (and according to Android docs this can also be used in other shared instances).

----------------------------------------

Now in the new Jetpack Navigation pattern, it is recommended to use a &quot;One Activity / Many Fragments&quot; architecture. This means that the activity lives for the whole time the app is being used. 

i.e. any shared `ViewModel` instances that are scoped to `Activity` lifecycle will never be cleared - the memory remains in constant use.

With a view to preserving memory and using as little as required at any point in time, it would be nice to be able to clear shared `ViewModel` instances when no longer required.

-------------------------------

How can one manually clear a `ViewModel` from it&#39;s `ViewModelStore` or holder fragment?


  [1]: https://stackoverflow.com/a/53653341/383414
  [2]: https://developer.android.com/reference/android/arch/lifecycle/ViewModel

Manually clearing an Android ViewModel?

Let&#39;s say that we have two fragments: `MainFragment` and `SelectionFragment`. The second one is build for selecting some object, e.g. an integer. There are different approaches in receiving result from this second fragment like callbacks, buses etc. 

Now, if we decide to use Navigation Architecture Component in order to navigate to second fragment we can use this code:

    NavHostFragment.findNavController(this).navigate(R.id.action_selection, bundle)

where `bundle` is an instance of `Bundle` (of course). As you can see there is no access to `SelectionFragment` where we could put a callback. The question is, how to receive a result with Navigation Architecture Component?

How to get a result from fragment using Navigation Architecture Component?

I am using [Navigation][1] from [Android Jetpack][2] to navigate between  screens.
Now I want to set startDestination dynamically. 

I have an Activity named MainActivity
And two Fragments, FragmentA &amp; FragmentB.

    var isAllSetUp : Boolean = // It is dynamic and I’m getting this from Preferences.
    
        If(isAllSetUp)
        {
         // show FragmentA
        }
        else
        {
         //show FragmentB
        }

I want to set above flow using Navigation Architecture Component. Currently I have used startDestionation as below but it’s not fulfilling my requirement.

    &lt;navigation xmlns:android=&quot;http://schemas.android.com/apk/res/android&quot;
       xmlns:app=&quot;http://schemas.android.com/apk/res-auto&quot;
       xmlns:tools=&quot;http://schemas.android.com/tools&quot;
       android:id=&quot;@+id/lrf_navigation&quot;
       app:startDestination=&quot;@id/fragmentA&quot;&gt;
    
       &lt;fragment
           android:id=&quot;@+id/fragmentA&quot;
           android:name=&quot;com.mindinventory.FragmentA&quot;
           android:label=&quot;fragment_a&quot;
           tools:layout=&quot;@layout/fragment_a&quot; /&gt;
    &lt;/navigation&gt;



Is it possible to set startDestination conditionally using Android Navigation Architecture Component?


  [1]: https://developer.android.com/topic/libraries/architecture/navigation/navigation-implementing
  [2]: https://developer.android.com/jetpack/

Is it possible to set startDestination conditionally using Android Navigation Architecture Component(Android Jetpack)?

    fun createListItem(itemIndex: Int) {
    Padding(left = 8.dp, right = 8.dp, top = 8.dp, bottom = 8.dp) {
        FlexRow(crossAxisAlignment = CrossAxisAlignment.Center) {
            expanded(1.0f) {
                Text(&quot;Item $itemIndex&quot;)
            }
            inflexible {
                Button(
                    &quot;Button $itemIndex&quot;,
                    style = ContainedButtonStyle(),
                    onClick = {
                        Toast.makeText(
                            this@MainActivity,
                            &quot;Item name $itemIndex&quot;,
                            Toast.LENGTH_SHORT
                        ).show()
                    })

            }
        }
      }
    }



I try to make Toast in a normal way. but I got the error I tried a lot of multiples source but failed. 

How to get Context in Jetpack Compose

I been struggling a lot thinking about where to place Android Services in the new [Android recommended Architecture][1]. I came up with many possible solutions, but I cannot make up my mind about which one is the best approach.

I did a lot of research, and I couldn&#39;t find any useful guideline nor tutorial. The only hint I found about where to place the Service in my app architecture is this one, from @JoseAlcerreca [Medium post](https://medium.com/androiddevelopers/viewmodels-and-livedata-patterns-antipatterns-21efaef74a54)

&gt; Ideally, ViewModels shouldn’t know anything about Android. This improves testability, leak safety and modularity. A general rule of thumb is to make sure there are no android.* imports in your ViewModels (with exceptions like android.arch.*). The same applies to presenters.

According to that, I should place my Android Services on the top of my Architecture Components hierarchy, at the same level as my Activities and Fragments. That&#39;s because Android Services are part of the Android framework, so ViewModels shouldn&#39;t know about them.

Now, I will explain briefly my scenario, but only to make the panorama clearer, not because I want an answer for this specific scenario.

- I have an Android Application that has a MainActivity with many fragments in it, all of them tied together in a BottomNavBar.
- I have a BluetoothService bound to myActivity and one of its fragments (because I want the Service to have the same lifecycle as the Activty but I also want to interact with it directly from my fragment).
- The fragment interacts with the BluetoothService to get two types of information:
    - Information about the state of the Bluetooth connection. Doesn&#39;t need to be persisted.
    - Data that comes from the Bluetooth Device (it is a Scale, so weight and body composition in this case). Needs to be persisted.

Here are the 3 different architectures I can think of:

**LiveData inside AndroidService**


***UPDATE: This is the approach I personally went with at the time because it worked well and allowed me to get it done relatively fast. However, I suggest following the updated answer by Jeel Vankhede for what seems to be a more &quot;idiomatic&quot; implementation.***

[![LiveData inside Android Service arch][2]][2] 

 - The LiveData with the state of the connection and with the weight
 measurements coming from the Bluetooth Device are inside the BluetoothService.
 - The Fragment can trigger operations in the BluetoothService (scanDevices for example)
 - The Fragment observes the LiveData about the state of the connection
   and adapts the UI accordingly (for example, enable a button if the
   state is connected).
 - The Fragment observes the LiveData of the new weight measurements. If a new weight measurement comes from the BluetoothDevice, the Fragment then tells its own ViewModel to save the new data. It is done via a Repository class.

**Shared ViewModel between fragment and AndroidService**
[![Shared ViewModel arch][3]][3]

 - The Fragment can trigger operations in the BluetoothService (scanDevices for example)
 - The BluetoothService updates the Bluetooth related LiveData in the shared ViewModel.
 - The Fragment observes the LiveData in its own ViewModel.

**Service ViewModel**
[![Service ViewMOdel arch][4]][4]

 - The Fragment can trigger operations in the BluetoothService (scanDevices for example)
 - The BluetoothService updates the Bluetooth related LiveData in its own ViewModel.
 - The Fragment observes the LiveData in its own ViewModel and the BluetoothService ViewModel.

----------------

I am pretty sure I should place them on top of the architecture and treat them just like an Activity/Fragment, because BoundServices are part of the Android Framework, they are managed by the Android OS and they are bound to other Activities and Fragments. In that case, I don&#39;t know what&#39;s the best way to interact with LiveData, ViewModels and Activities/Fragments.

Some might think that they should be considered as a DataSource (since in my case it&#39;s getting data from a scale using Bluetooth), but I don&#39;t think this is a good idea, because of all what I&#39;ve said in the previous paragraph and specially [because of what it says here][5]: 

&gt; Avoid designating your app&#39;s entry points—such as activities,
&gt; **services**, and broadcast receivers—as sources of data. Instead, they should only coordinate with other components to retrieve the
&gt; subset of data that is relevant to that entry point. Each app
&gt; component is rather short-lived, depending on the user&#39;s interaction
&gt; with their device and the overall current health of the system.

So, finally, my question is: 

**Where should we place our Android (Bound) Services and what is their relation with the other architectural components? Is any of these alternatives a good approach?**

  [1]: https://developer.android.com/jetpack/docs/guide
  [2]: https://i.stack.imgur.com/nWGH8.png
  [3]: https://i.stack.imgur.com/mq5Lg.png
  [4]: https://i.stack.imgur.com/rGrl6.png
  [5]: https://developer.android.com/jetpack/docs/guide#best-practices
  [6]: https://github.com/googlesamples/android-architecture-components/issues/20#issuecomment-351826757

BoundService + LiveData + ViewModel best practice in new Android recommended architecture

I am using the new [Navigation](https://developer.android.com/topic/libraries/architecture/navigation/) component from Android Jetpack.

The root Activity setup is quite simple:

&lt;!-- language: kotlin --&gt;

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        setSupportActionBar(toolbar)
        
        val navController = findNavController(R.id.navigationFragment)
        setupActionBarWithNavController(navController)
    
        bottomNavigationView.setupWithNavController(navController)
    }

It works well when the Fragment&#39;s title is defined in the navigation graph. But for one Fragment, I want to set the title dynamically.

I tried with `findNavController().currentDestination.label = &quot;Hello world&quot;` but it does nothing.

I could of course use a trick like `(activity as? AppCompatActivity)?.supportActionBar?.title = &quot;Hello world&quot;`, but I feel that it will break the magic that `setupActionBarWithNavController()` does for me. It there any way to update the Action Bar title dynamically? 

Dynamic ActionBar title from a Fragment using AndroidX Navigation

Basically, I have the following navigation graph:

[![enter image description here][1]][1]


I want to change my starting point in navigation graph to `fragment 2` right after reaching it (in order to prevent going back to `fragment 1` when pressing back button - like with the splash screen).

This is my code:

    navGraph = navController.getGraph();
    navGraph.setStartDestination(R.id.fragment2);
    navController.setGraph(navGraph);

But, obviously it&#39;s not working and it gets back to `fragment 1` after pressing back button.

Am I doing it wrong?
Is there any other solution?


  [1]: https://i.stack.imgur.com/Y3yo0.jpg

How to change start destination of a navigation graph programmatically?

I have one case and wish to implement it by arch navigation component. For example I have 2 Nav Graphs (main and nested). Can I call main graph from nested and how?
 [![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/rbFR3.png

New navigation component from arch with nested navigation graph

Is it possible to use the new Navigation Architecture Component with DialogFragment? Do I have to create a custom Navigator?

I would love to use them with the new features in my navigation graph.

Navigation Architecture Component - Dialog Fragments

I&#39;m creating a layout with Jetpack Compose and there is a column. I would like center items inside this column:

     Column(modifier = ExpandedWidth) {
            Text(text = item.title)
            Text(text = item.description)
     }

Jetpack Compose - Column - Gravity center

I&#39;ve seen the developer keynote of Google I/O 2018, and I&#39;ve read the jetpack homepage on Android developer website, but I cannot make sense of what it actually is. To me it seems like just a new name for a bunch of APIs we already use. Is there going to be something that the IDE does for us or something that&#39;s helpful while coding? All the components in Jetpack point to their original Android documentation, and don&#39;t actually showcase any difference than before. Can someone explain in simple terms what Jetpack actually does for me as a developer, apart from clubbing documentation on a web page?

What exactly is Android Jetpack?

I want to schedule nightly database updates. So I use new Android WorkManager. My understanding is that once scheduled it will always run in the background independently from the app&#39;s lifecycle. 
Is that right? My first tests show that Work is only being performed when the app is running.

    val locationWork = PeriodicWorkRequest.Builder(UpdateDatabaseWorker::class.java, 24, TimeUnit.HOURS)
                            .addTag(&quot;DATABASE_UPDATE_SERVICE&quot;)
                            .build()
    WorkManager.getInstance().enqueue(locationWork)

All Android Jetpack Solutions on Gang of Coders

Total of 26 Android Jetpack Solutions