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Handling View State and Events
with RainbowCake
Márton Braun
zsmb.co zsmb13
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RainbowCake
rainbowcake/rainbowcake
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RainbowCake
rainbowcake/rainbowcake
An Android architecture framework
library
test
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RainbowCake
rainbowcake/rainbowcake
An Android architecture library
concept
framework
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RainbowCake
rainbowcake/rainbowcake
An Android architecture concept
thingie
library
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RainbowCake
rainbowcake/rainbowcake
An Android architecture thingie
framework
concept
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RainbowCake
rainbowcake/rainbowcake
An Android architecture framework
test
thingie
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RainbowCake
rainbowcake/rainbowcake
An Android architecture framework
libraries
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RainbowCake
rainbowcake/rainbowcake
An Android architecture framework
libraries
guidance
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RainbowCake
rainbowcake/rainbowcake
An Android architecture framework
libraries
guidance
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RainbowCake
rainbowcake/rainbowcake
Threading
Dependency injection
Layers
View state handling
Navigation
Models
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MvRx
airbnb/MvRx
Orbit MVI
babylonhealth/orbit-mvi
Roxie
ww-tech/roxie
Mosby
sockeqwe/mosby
Eiffel
etiennelenhart/Eiffel
Uniflow
uniflow-kt/uniflow-kt
MVICore
badoo/MVICore
RainbowCake
rainbowcake/rainbowcake
Mobius
spotify/mobius
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2020
2019
Start of
development
Moved into
a library
Workshop
Modules
Koin support Testing module
Repackage, website launch
GitHub, MavenCentral AndroidX
1.0
MVICore
MvRx
Orbit MVI
Uniflow
Roxie
[0]
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ItemApi
ItemDao
NetworkDataSource
DiskDataSource
ShopInteractor
UserInteractor
ProfilePresenter CartPresenter
HomePresenter
ProfileViewModel CartViewModel
HomeViewModel
CartViewState
ProfileViewState
HomeViewState
CartFragment
ProfileFragment
HomeFragment
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Dao
Data source
Interactor
Presenter
ViewModel
ViewState
Fragment
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ViewState
ViewModel
Presenter
Interactor
Data source
Dao
Fragment
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ViewModel
Presenter
Interactor
Data source
Fragment
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RainbowCake
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Data source
Interactor
Presenter
ViewModel
Fragment
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MVVM
View access through an
interface
Separation of View and
business logic
Component between
View and Model
MVP
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MVVM
View access through an
interface
Separation of View and
business logic
Component between
View and Model
MVP
Separation of View and
business logic
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MVVM
View access through an
interface
Separation of View and
business logic
Component between
View and Model
MVP
Separation of View and
business logic
Component between
View and Model
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MVVM
View access through an
interface
Separation of View and
business logic
Component between
View and Model
MVP
View access through an
interface
Separation of View and
business logic
Component between
View and Model
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Observable state
exposed to the View
MVVM
View access through an
interface
Separation of View and
business logic
Component between
View and Model
MVP
View access through an
interface
Separation of View and
business logic
Component between
View and Model
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View access through an
interface
MVVM
Separation of View and
business logic
Component between
View and Model
Observable state
exposed to the View
MVP
View access through an
interface
Separation of View and
business logic
Component between
View and Model
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MVVM
Separation of View and
business logic
Component between
View and Model
Observable state
exposed to the View
Data binding*
MVP
View access through an
interface
Separation of View and
business logic
Component between
View and Model
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MVVM
Separation of View and
business logic
Component between
View and Model
Observable state
exposed to the View
Data binding*
MVI
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MVVM
Separation of View and
business logic
Component between
View and Model
Observable state
exposed to the View
Data binding*
MVI
Single View state object
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MVVM
Separation of View and
business logic
Component between
View and Model
Observable state
exposed to the View
Data binding*
MVI
Single View state object
Reactive data streams
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MVVM
Separation of View and
business logic
Component between
View and Model
Observable state
exposed to the View
Data binding*
MVI
Single View state object
Reactive data streams
Input events as objects
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MVVM
Separation of View and
business logic
Component between
View and Model
Observable state
exposed to the View
Data binding*
MVI
Single View state object
Reactive data streams
Input events as objects
Reducer
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MVVM
Separation of View and
business logic
Component between
View and Model
Observable state
exposed to the View
Data binding*
MVI
Single View state object
Reactive data streams
Input events as objects
Reducer
[1]
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State handling
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No content
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app
RainbowCake
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app
RainbowCake
abstract class RainbowCakeViewModel ViewModel()
class ProfileViewModel : RainbowCakeViewModel()
:
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app
RainbowCake
abstract class RainbowCakeViewModel ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
:
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app
RainbowCake
abstract class RainbowCakeViewModel ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
:
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app
RainbowCake
abstract class RainbowCakeViewModel ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
:
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app
RainbowCake
abstract class RainbowCakeViewModel ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
:
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app
RainbowCake
abstract class RainbowCakeViewModel ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
:
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app
RainbowCake
abstract class RainbowCakeViewModel ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
:
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app
RainbowCake
abstract class RainbowCakeViewModel : ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
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app
RainbowCake
abstract class RainbowCakeViewModel : ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
sealed class ProfileViewState
object Loading : ProfileViewState()
data class ProfileLoaded(val name: String) : ProfileViewState()
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app
RainbowCake
abstract class RainbowCakeViewModel : ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state
}
class ProfileViewModel : RainbowCakeViewModel()
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app
RainbowCake
abstract class RainbowCakeViewModel
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state.distinct()
}
class ProfileViewModel : RainbowCakeViewModel()
: ViewModel() {
[3]
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
)
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state.distinct()
}
class ProfileViewModel : RainbowCakeViewModel()
: ViewModel() {
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state.distinct()
init {
_state.value = initialState
}
}
class ProfileViewModel : RainbowCakeViewModel()
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state.distinct()
init {
_state.value = initialState
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
_state.value = Loading
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state.distinct()
init {
_state.value = initialState
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
_state.value = Loading
_state.value = ProfileLoaded(loadUserName())
}
}
}
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state.distinct()
init {
_state.value = initialState
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
_state.value =
_state.value =
}
}
}
_state.value!!.copy(isLoading = true)
_state.value!!.copy(name = )
loadUserName()
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _state: MutableLiveData = MutableLiveData()
val state: LiveData = _state.distinct()
init {
_state.value = initialState
}
}
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RainbowCake
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
}
val state: LiveData = _state.distinct()
init {
_state.value = initialState
}
val _state: MutableLiveData = MutableLiveData()
private
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app
RainbowCake
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
_state.value = _state.value!!.copy(isLoading = true)
_state.value = _state.value!!.copy(name = loadUserName())
}
}
}
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
}
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app
RainbowCake
=
=
viewState
viewState
viewState
viewState
.copy(isLoading = true)
.copy(name = loadUserName())
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
}
}
}
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
}
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app
RainbowCake
loadUserName()
( )
Loading
ProfileLoaded
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
viewState =
viewState =
}
}
}
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
viewState = Loading
viewState = ProfileLoaded(loadUserName())
}
}
}
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
viewState = Loading
viewState = ProfileLoaded(loadUserName())
}
}
}
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.setValue(value)
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
viewState = Loading
viewState = ProfileLoaded(loadUserName())
}
}
}
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
viewState = Loading
viewState = ProfileLoaded(loadUserName())
}
}
}
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
}
println(viewState is Loading)
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
viewModelScope.launch {
viewState = Loading
viewState = ProfileLoaded(loadUserName())
}
}
}
[4]
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app
RainbowCake
) : ViewModel() {
protected var viewState: VS
get() = _state.value!!
set(value) {
_state.postValue(value)
}
}
class ProfileViewModel : RainbowCakeViewModel(Loading) {
fun loadProfile() {
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app
RainbowCake
abstract class RainbowCakeFragment : Fragment()
class ProfileFragment : RainbowCakeFragment()
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RainbowCake
{
protected lateinit var viewModel: ?
}
app
class ProfileFragment : RainbowCakeFragment()
abstract class RainbowCakeFragment : Fragment()
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app
RainbowCake
abstract class RainbowCakeFragment Fragment() {
protected lateinit var viewModel VM
}
class ProfileFragment : RainbowCakeFragment()
:
:
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app
RainbowCake
abstract class RainbowCakeFragment : Fragment() {
protected lateinit var viewModel: VM
}
class ProfileFragment : RainbowCakeFragment()
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app
RainbowCake
abstract class RainbowCakeFragment> : Fragment() {
protected lateinit var viewModel: VM
}
class ProfileFragment : RainbowCakeFragment()
:
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RainbowCake
?
app
abstract class RainbowCakeFragment>
protected lateinit var viewModel: VM
}
class ProfileFragment : RainbowCakeFragment()
: : Fragment(
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app
RainbowCake
abstract class RainbowCakeFragment>
protected lateinit var viewModel: VM
}
class ProfileFragment : RainbowCakeFragment()
: Fragment() {
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app
RainbowCake
abstract class RainbowCakeFragment>
: Fragment() {
protected lateinit var viewModel: VM
}
class ProfileFragment : RainbowCakeFragment()
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RainbowCake
abstract class RainbowCakeFragment>
: Fragment() {
protected lateinit var viewModel
abstract fun provideViewModel(): VM
@CallSuper
override fun onAttach(context: Context) {
super.onAttach(context)
viewModel = provideViewModel()
}
app
class ProfileFragment : RainbowCakeFragment()
:
: VM
}
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RainbowCake
app
class ProfileFragment : RainbowCakeFragment() {
}
abstract fun provideViewModel(): VM
@CallSuper
override fun onAttach(context: Context) {
super.onAttach(context)
viewModel = provideViewModel()
}
override fun provideViewModel() = getViewModelFromFactory()
abstract class RainbowCakeFragment>
: Fragment() {
protected lateinit var viewModel: VM
}
[5]
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RainbowCake
app
class ProfileFragment : RainbowCakeFragment() {
}
abstract fun provideViewModel(): VM
@CallSuper
override fun onAttach(context: Context) {
super.onAttach(context)
viewModel = provideViewModel()
}
override fun provideViewModel() = getViewModelFromFactory()
abstract class RainbowCakeFragment>
: Fragment() {
protected lateinit var viewModel: VM
}
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RainbowCake
@CallSuper
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.state.observe(viewLifecycleOwner, Observer { viewState ->
})
}
app
class ProfileFragment : RainbowCakeFragment() {
}
abstract class RainbowCakeFragment>
: Fragment() {
protected lateinit var viewModel: VM
}
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RainbowCake
@CallSuper
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.state.observe(viewLifecycleOwner, Observer { viewState ->
})
}
app
class ProfileFragment : RainbowCakeFragment() {
}
abstract class RainbowCakeFragment>
: Fragment() {
protected lateinit var viewModel: VM
}
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app
RainbowCake
:
protected lateinit var viewModel: VM
abstract class RainbowCakeFragment>
: Fragment() {
abstract fun render(viewState VS)
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.state.observe(viewLifecycleOwner, Observer { viewState ->
viewState?.let { render(it) }
})
}
@CallSuper
}
class ProfileFragment : RainbowCakeFragment() {
override fun render(viewState: ProfileViewState) {
when (viewState) {
Loading -> { ... }
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app
RainbowCake
override fun render(viewState: ProfileViewState) {
when (viewState) {
Loading -> { ... }
is ProfileLoaded -> { ... }
}
}
:
abstract fun render(viewState VS)
}
abstract class RainbowCakeFragment>
: Fragment() {
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.state.observe(viewLifecycleOwner, Observer { viewState ->
viewState?.let { render(it) }
})
}
class ProfileFragment : RainbowCakeFragment() {
}
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app
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
RainbowCake
abstract class RainbowCakeFragment>
: Fragment() {
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.state.observe(viewLifecycleOwner, Observer { viewState ->
viewState?.let { render(it) }
})
}
abstract fun render(viewState: VS)
}
override fun render(viewState: ProfileViewState) {
when (viewState) {
Loading -> { ... }
is ProfileLoaded -> { ... }
}
}
class ProfileFragment : RainbowCakeFragment() {
}
.exhaustive
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app
override fun render(viewState: ProfileViewState) {
when (viewState) {
Loading -> { ... }
is ProfileLoaded -> { ... }
}
}
class ProfileFragment : RainbowCakeFragment() {
}
.exhaustive
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.loadProfile()
}
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Event handling
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RainbowCake
app
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
}
class ProfileViewModel : RainbowCakeViewModel(Loading)
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RainbowCake
app
class ProfileViewModel : RainbowCakeViewModel(Loading)
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
}
SingleShotLiveData()
events: MutableLiveData =
val
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RainbowCake
app
class ProfileViewModel : RainbowCakeViewModel(Loading)
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
}
SingleShotLiveData()
events: MutableLiveData =
val
[7]
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RainbowCake
app
class ProfileViewModel : RainbowCakeViewModel(Loading)
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected _
val events: LiveData = _events
}
SingleShotLiveData()
val events: MutableLiveData =
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RainbowCake
app
class ProfileViewModel : RainbowCakeViewModel(Loading)
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _events: MutableLiveData =
SingleShotLiveData()
val events: LiveData = _events
}
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RainbowCake
app
class ProfileViewModel : RainbowCakeViewModel(Loading)
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _events: MutableLiveData =
SingleShotLiveData()
val events: LiveData = _events
}
abstract class RainbowCakeFragment<
VS : Any, VE : Any, VM : RainbowCakeViewModel
> : Fragment
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RainbowCake
app
class ProfileViewModel : RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _events: MutableLiveData =
SingleShotLiveData()
val events: LiveData = _events
}
abstract class RainbowCakeFragment<
VS : Any, VE : Any, VM : RainbowCakeViewModel
> : Fragment
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RainbowCake
app
class ProfileViewModel : RainbowCakeViewModel(Loading)
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _events: MutableLiveData =
SingleShotLiveData()
val events: LiveData = _events
}
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RainbowCake
app
class ProfileViewModel : RainbowCakeViewModel(Loading)
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _events: MutableLiveData =
SingleShotLiveData()
val events: LiveData = _events
}
interface OneShotEvent
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RainbowCake
app
class ProfileViewModel RainbowCakeViewModel(Loading)
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
protected val _events: MutableLiveData =
SingleShotLiveData()
val events: LiveData = _events
}
interface OneShotEvent
:
{
object SaveFailedEvent : OneShotEvent
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RainbowCake
private
app
class ProfileViewModel RainbowCakeViewModel(Loading) {
object SaveFailedEvent : OneShotEvent
fun saveProfile() {
_events.value = SaveFailedEvent
}
}
interface OneShotEvent
:
}
val events: LiveData = _events
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
SingleShotLiveData()
val _events: MutableLiveData =
protected
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RainbowCake
private
app
class ProfileViewModel RainbowCakeViewModel(Loading) {
object SaveFailedEvent : OneShotEvent
fun saveProfile() {
_events.value = SaveFailedEvent
}
}
interface OneShotEvent
:
}
val events: LiveData = _events
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
SingleShotLiveData()
val _events: MutableLiveData =
protected
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app
RainbowCake
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
interface OneShotEvent
}
val events: LiveData = _events
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
SingleShotLiveData()
val _events: MutableLiveData =
private
class ProfileViewModel RainbowCakeViewModel(Loading) {
object SaveFailedEvent : OneShotEvent
fun saveProfile() {
_events.value = SaveFailedEvent
}
}
:
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app
RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveData =
SingleShotLiveData()
val events: LiveData = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
interface OneShotEvent
class ProfileViewModel : RainbowCakeViewModel(Loading) {
object SaveFailedEvent : OneShotEvent
fun saveProfile() {
postEvent(SaveFailedEvent)
}
}
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RainbowCake
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RainbowCake
abstract fun provideViewModel(): VM
@CallSuper
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.state.observe(viewLifecycleOwner, Observer { viewState ->
viewState?.let { render(it) }
})
}
abstract fun render(viewState: VS)
override fun provideViewModel() = getViewModelFromFactory()
override fun render(viewState: ProfileViewState) {
when (viewState) {
Loading -> { ... }
is ProfileLoaded -> { ... }
}.exhaustive
}
override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
super.onViewCreated(view, savedInstanceState)
viewModel.loadProfile()
}
class ProfileFragment : RainbowCakeFragment() {
}
}
@CallSuper
override fun onAttach(context: Context) {
super.onAttach(context)
viewModel = provideViewModel()
}
protected lateinit var viewModel: VM
abstract class RainbowCakeFragment> : Fragment() {
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app
RainbowCake
class ProfileFragment : RainbowCakeFragment() {
}
}
@CallSuper
override fun onAttach(context: Context) {
super.onAttach(context)
viewModel = provideViewModel()
}
protected lateinit var viewModel: VM
abstract class RainbowCakeFragment>
: Fragment() {
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RainbowCake
@CallSuper
override fun onAttach(context: Context) {
super.onAttach(context)
viewModel = provideViewModel()
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
abstract class RainbowCakeFragment>
: Fragment() {
protected lateinit var viewModel: VM
class ProfileFragment : RainbowCakeFragment() {
}
override fun onEvent(event: OneShotEvent) {
when (event) {
is SaveFailedEvent -> showErrorMessage()
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RainbowCake
@CallSuper
override fun onAttach(context: Context) {
super.onAttach(context)
viewModel = provideViewModel()
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
abstract class RainbowCakeFragment>
: Fragment() {
protected lateinit var viewModel: VM
class ProfileFragment : RainbowCakeFragment() {
}
override fun onEvent(event: OneShotEvent) {
when (event) {
is SaveFailedEvent -> showErrorMessage()
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RainbowCake
@CallSuper
override fun onAttach(context: Context) {
super.onAttach(context)
viewModel = provideViewModel()
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
abstract class RainbowCakeFragment>
: Fragment() {
class ProfileFragment : RainbowCakeFragment() {
}
override fun onEvent(event: OneShotEvent) {
when (event) {
is SaveFailedEvent -> showErrorMessage()
}
}
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Fragment
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Fragment 1
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app
RainbowCake
class ProfileViewModel : RainbowCakeViewModel(Loading) {
object SaveFailedEvent : OneShotEvent
fun saveProfile() {
postEvent(SaveFailedEvent)
}
}
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveData =
SingleShotLiveData()
val events: LiveData = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
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app
RainbowCake
class ProfileViewModel : RainbowCakeViewModel(Loading) {
object SaveFailedEvent : OneShotEvent
fun saveProfile() {
postEvent(SaveFailedEvent)
}
}
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveData =
QueuedSingleShotLiveData()
val events: LiveData = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
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Fragment
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Fragment 1
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Fragment 1 2
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Fragment 1 2
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RainbowCake
interface LiveDataCollection {
fun observe(owner: LifecycleOwner, observer: Observer)
}
interface MutableLiveDataCollection : LiveDataCollection {
fun setValue(value: T?)
fun postValue(value: T?)
}
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RainbowCake
class MutableLiveDataCollectionImpl(
private val factory: () -> MutableLiveData
) : MutableLiveDataCollection {
}
interface LiveDataCollection {
fun observe(owner: LifecycleOwner, observer: Observer)
}
interface MutableLiveDataCollection : LiveDataCollection {
fun setValue(value: T?)
fun postValue(value: T?)
}
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RainbowCake
class MutableLiveDataCollectionImpl(
private val factory: () -> MutableLiveData
) : MutableLiveDataCollection {
}
interface LiveDataCollection {
fun observe(owner: LifecycleOwner, observer: Observer)
}
interface MutableLiveDataCollection : LiveDataCollection {
fun setValue(value: T?)
fun postValue(value: T?)
}
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RainbowCake
class MutableLiveDataCollectionImpl(
private val factory: () -> MutableLiveData
) : MutableLiveDataCollection {
private val activeLiveData: MutableSet> = mutableSetOf()
interface LiveDataCollection {
fun observe(owner: LifecycleOwner, observer: Observer)
}
interface MutableLiveDataCollection : LiveDataCollection {
fun setValue(value: T?)
fun postValue(value: T?)
}
}
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RainbowCake
/* ... */
interface LiveDataCollection {
fun observe(owner: LifecycleOwner, observer: Observer)
}
interface MutableLiveDataCollection : LiveDataCollection {
fun setValue(value: T?)
fun postValue(value: T?)
}
}
class MutableLiveDataCollectionImpl(
private val factory: () -> MutableLiveData
) : MutableLiveDataCollection {
private val activeLiveData: MutableSet> = mutableSetOf()
override fun observe(owner: LifecycleOwner, observer: Observer) {
}
val liveData = factory()
activeLiveData += liveData
// ...
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RainbowCake
val liveData = factory()
activeLiveData += liveData
// ...
interface LiveDataCollection {
fun observe(owner: LifecycleOwner, observer: Observer)
}
interface MutableLiveDataCollection : LiveDataCollection {
fun setValue(value: T?)
fun postValue(value: T?)
}
}
override fun setValue(value: T?) {
activeLiveData.forEach { it.setValue(value) }
}
override fun postValue(value: T?) {
activeLiveData.forEach { it.postValue(value) }
}
class MutableLiveDataCollectionImpl(
private val factory: () -> MutableLiveData
) : MutableLiveDataCollection {
private val activeLiveData: MutableSet> = mutableSetOf()
override fun observe(owner: LifecycleOwner, observer: Observer) { }
/* ... */
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveData =
QueuedSingleShotLiveData()
val events: LiveData = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveData =
QueuedSingleShotLiveData()
val events: LiveData = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val events: LiveData = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val events: LiveData = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val events: LiveDataCollection = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
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abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val _events: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val events: LiveDataCollection = _events
protected fun postEvent(event: OneShotEvent) {
_events.postValue(event)
}
}
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
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Fragment 1
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val viewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::ActiveOnlySingleShotLiveData)
val events: LiveDataCollection = viewEvents
protected fun postEvent(event: OneShotEvent) {
viewEvents.postValue(event)
}
}
private val queuedViewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val queuedEvents: LiveDataCollection = queuedViewEvents
protected fun postQueuedEvent(event: QueuedOneShotEvent) {
queuedViewEvents.postValue(event)
}
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val viewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::ActiveOnlySingleShotLiveData)
val events: LiveDataCollection = viewEvents
protected fun postEvent(event: OneShotEvent) {
viewEvents.postValue(event)
}
}
private val queuedViewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val queuedEvents: LiveDataCollection = queuedViewEvents
protected fun postQueuedEvent(event: QueuedOneShotEvent) {
queuedViewEvents.postValue(event)
}
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val viewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::ActiveOnlySingleShotLiveData)
val events: LiveDataCollection = viewEvents
protected fun postEvent(event: OneShotEvent) {
viewEvents.postValue(event)
}
}
private val queuedViewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val queuedEvents: LiveDataCollection = queuedViewEvents
protected fun postQueuedEvent(event: QueuedOneShotEvent) {
queuedViewEvents.postValue(event)
}
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val viewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::ActiveOnlySingleShotLiveData)
val events: LiveDataCollection = viewEvents
protected fun postEvent(event: OneShotEvent) {
viewEvents.postValue(event)
}
}
private val queuedViewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val queuedEvents: LiveDataCollection = queuedViewEvents
protected fun postQueuedEvent(event: QueuedOneShotEvent) {
queuedViewEvents.postValue(event)
}
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abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val viewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::ActiveOnlySingleShotLiveData)
val events: LiveDataCollection = viewEvents
protected fun postEvent(event: OneShotEvent) {
viewEvents.postValue(event)
}
}
private val queuedViewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val queuedEvents: LiveDataCollection = queuedViewEvents
protected fun postQueuedEvent(event: QueuedOneShotEvent) {
queuedViewEvents.postValue(event)
}
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abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val viewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::ActiveOnlySingleShotLiveData)
val events: LiveDataCollection = viewEvents
protected fun postEvent(event: OneShotEvent) {
viewEvents.postValue(event)
}
}
private val queuedViewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val queuedEvents: LiveDataCollection = queuedViewEvents
protected fun postQueuedEvent(event: QueuedOneShotEvent) {
queuedViewEvents.postValue(event)
}
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RainbowCake
abstract class RainbowCakeViewModel(
initialState: VS
) : ViewModel() {
private val viewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::ActiveOnlySingleShotLiveData)
val events: LiveDataCollection = viewEvents
protected fun postEvent(event: OneShotEvent) {
viewEvents.postValue(event)
}
}
private val queuedViewEvents: MutableLiveDataCollection =
MutableLiveDataCollectionImpl(::QueuedSingleShotLiveData)
val queuedEvents: LiveDataCollection = queuedViewEvents
protected fun postQueuedEvent(event: QueuedOneShotEvent) {
queuedViewEvents.postValue(event)
}
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RainbowCake
interface OneShotEvent
interface QueuedOneShotEvent : OneShotEvent
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
}
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
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interface OneShotEvent
interface QueuedOneShotEvent : OneShotEvent
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
}
protected open fun onEvent(event: OneShotEvent) {}
}
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
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RainbowCake
interface OneShotEvent
interface QueuedOneShotEvent : OneShotEvent
abstract class RainbowCakeFragment>
: Fragment() {
override fun onAttach(context: Context) {
// ...
viewModel.queuedEvents.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
}
protected open fun onEvent(event: OneShotEvent) {}
}
viewModel.events.observe(this, Observer { event ->
event?.let { onEvent(it) }
})
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Fragment
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But… these are all hacks!
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RainbowCake
rainbowcake/rainbowcake
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RainbowCake
rainbowcake/rainbowcake
rainbowcake.dev
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RainbowCake
rainbowcake/rainbowcake
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RainbowCake
rainbowcake/rainbowcake
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zsmb13
zsmb.co/talks
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Handling View State and
Events with RainbowCake
zsmb.co/talks
zsmb13
Márton Braun › Built on Jetpack
› Single view state
› Two event streams
› Many LiveData hacks