Mobile App Development 2022W Lecture 10
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Video
Video from the lecture given on February 11, 2022 is now available:
Video is also available through Brightspace (Resources->Zoom Meetings (Recordings, etc.)->Cloud Recordings tab). Note that here you'll also see chat messages.
Notes
Lecture 10
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introduce Assignment 2
continue with Tutorial 5
Go ahead and download android studio before next Wednesday
- give it time to run and update itself
Plain text files can have different line endings
- CR, \r <--- old MacOS (like, really old)
- LF, \n <--- Linux, UNIX, modern macOS
- CR+LF, \r\n <--- windows
When you have a controller in Storyboard that can send events, those events are received by functions that are marked with "@IBAction"
- you then have to connect the function to the correct storyboard outlet
for the sent event
AnalysisResult view in textanalyzer-2 corresponds to
updateAnalysis in textanalyzer-3.
- updateAnalysis is called in three places
- when the first view is displayed
- when the user types anything into the input field
- when a menu item is selected
- but, when is AnalysisResult called?
- it is run whenever it needs to be, automatically
- it will run when Contentview is put on the screen
(because AnalysisResult is included), and it will run
whenever mode and userInput change
- i.e., when a menu item is selected and when a user types
- but these calls are implicit, not explicit, we don't
have to put them in manually, they just happen
Remember, in SwiftUI, when a @State variable changes, any views dependent on those state variables are automatically updated (i.e., their code is re-run)
When you have to do updates manually, it is very easy to skip or to do the wrong ones
- then your interface is stale, doesn't reflect the underlying app state
- leads to lots of bugs
That's why the modern way is to do things more declaratively
- tell the system what the screen looks like based on data
- the framework figures out when the screen needs to be updated based
on changes to designated data
@State variables are the actual "state"
@Binding variables are references to @State variables
- essentially pointers/call by reference
@State variables are really objects under the hood which do extra work whenever the object's properties are read from or written to
- the set's and get's are overridden with extra functionality