This simple Android app showcases how you might use a ViewModel and LiveData in your apps. You can get the article that accompanies this project on medium or developerlife.com.

The sample just has 1 Java file — MainActivity.java. This Activity loads its state from a StateViewModel, which contains two pieces of data.

Data # 1 - There’s a UUID String that is generate the first time this StateViewModel is created and this is displayed in the UI. This String does not change for the lifetime of the Activity. It is stable across configuration changes. So as you rotate the screen, and the Activity is destroyed and then recreated (but not finished), the same UUID String will be displayed in the UI. When you finish the Activity by pressing the back button, or by going to the task switcher and swiping the Activity away, then the ViewModel will be destroyed and onCleared() will be called.

Data # 2 - The ViewModel also creates a ScheduledExecutor that runs a simple task every second. This task simply updates a counter, and it generates a log message (“tick”, or “tock”). This Executor also sets the value of this counter in a CounterLiveData object. The UI actually subscribes to this LiveData object and when it changes the UI gets updated with the current count. This too is stable across configuration changes. When the Activity is finally finished, the onCleared() method actually shuts the executor down. Also, you have to be mindful of which thread the CounterLiveData’s value is set.

The Internet Engineering Task Force (IETF) points out that "Master-slave is an oppressive metaphor that will and should never become fully detached from history" as well as "In addition to being inappropriate and arcane, the master-slave metaphor is both technically and historically inaccurate." There's lots of more accurate options depending on context and it costs me nothing to change my vocabulary, especially if it is one less little speed bump to getting a new person excited about tech.

You might say, "I'm all for not using master in master-slave technical relationships, but this is clearly an instance of master-copy, not master-slave" but that may not be the case. Turns out the original usage of master in Git very likely came from another version control system (BitKeeper) that explicitly had a notion of slave branches.

• https://dev.to/lukeocodes/change-git-s-default-branch-from-master-19le
• https://www.hanselman.com/blog/EasilyRenameYourGitDefaultBranchFromMasterToMain.aspx

#blacklivesmatter