Saving UI state with ViewModel SavedState and Dagger
This repository contains a sample project that demonstrate the topic discussed in my article about ViewModel SavedState module, which part of the Android architecture lifecycle components.
Saved state use cases in the sample
To simulate a process stop, switch to Logcat and at the lefthand corner press the Stop button to stop the process while making sure that the right process is selected in the dropdown box.
Commit List screen
You will notice that CommitListViewModel is making use of SavedStateHandle to save the last seen page in the list.
If the app recovers from a process stop, the handle will load the last seen page. We then load the data up to that page.
Commit Detail screen
In this case, we're saving the state of the whole commit response object so that the next time the app recovers from a process stop, it will restore that last commit response object and will skip making a request to Github.
When you launch the app, pay attention to the logs in Logcat. You will see that when the activity is started for the first time, it will make the request
and then store the result in SavedStateHandle that is passed to CommitDetailViewModel. Then navigate away from the activity by simply
going to the home screen and then navigate back. You'll see in the logs that the previously stored response is loaded from
SavedStateHandle - indicating that the state has been restored after process death.
Libraries and architecture
The app is utilizing the MVVM design pattern for the UI with the help of the following libraries:
- AndroidX
- Architecture Components - ViewModel, Lifecycle, Navigation
- Material components library
- Constraint layout
- Retrofit2 + OkHttp
- Moshi
- Dagger2 + Hilt
- Timber
- Glide
- Kotlin coroutines
- Epoxy
License
Copyright 2020 Nimrod Dayan nimroddayan.com
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.