Data binding
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Presentation by DataBinding done by Leonid from GDG and me at "Sweetest aMazing" session at Google Cloud Next event.
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Data binding
- 1. Data Binding
- 2. Who we are? Leonid Olevsky leonid.olevsky@gmail.com Yonatan Levin levinyon@gmail.com Android Academy
- 4. Today findViewById Coordinates between the model and the views Create untestable code And more...
- 5. What is Data Binding? Model View ViewModel (MVVM) Ongoing link between an element in the user interface and a value When a variable’s value is updated, the display on the user’s screen changes automatically
- 6. Dependencies It's a support library - Android 2.1 (API level 7+) Gradle 1.3.0-beta4 or higher is required Beta release
- 7. Dependencies In a top-level build.gradle add In each module
- 8. Simple usage - Binding Data
- 9. Simple usage - Binding Data
- 11. Simple usage - Binding Data The magic Other option
- 12. Simple usage - Binding Events
- 14. More options Referencing static fields and methods in expressions
- 15. More options - include
- 16. Expression Language Mathematical + - / * % String concatenation + Logical && || Binary & | ^ Unary + - ! ~ Shift >> >>> << Comparison == > < >= <= instanceof Grouping () Literals - character, String, numeric, null Cast Method calls Field access Array access [] Ternary operator ?:
- 17. Expression Language Not supported this super new Explicit generic invocation
- 18. Observable Observable Objects listen for changes of all properties on that object ObservableFields listen for changes of a field of that object Observable Collections listen for changes on dynamic structures to hold data
- 20. ObservableFields
- 23. Our app
- 24. Architecture StarwarsActivity CrawlLoader OpeningCrawl mCrawlLoader.startLoading() new OpeningCrawl onLoadFinishListener.onLoadFinish(openingCrawl) Every ~5 seconds findViewById(R.id.asw_tv_episode); findViewById(R.id.asw_tv_crawl); mEpisodeTextView.setText(...); mCrawlTextView.setText(...); mCrawlTextView.startAnimation();
- 25. Data Binding could be the mess
- 26. Downside - Define stuff in XML - Not debuggable - XML not unit tested - Run-time errors instead compile time - Bad IDE support
- 27. MVP - The Best Simple Friend
- 28. Why MVP? - Decoupled layers - Easy to debug - Fully testable business logic, data model
- 29. MVP vs DataBinding Presenter react on what happen in the view, retrieves data, formats and display back in the view Data Binding will take over the main responsibilities of the presenter (react and display). Rest - will go to the enhanced Model - ViewModel
- 31. MVVM Architecture StarwarsActivity CrawlLoader OpeningCrawl mCrawlLoader.startLoading() new OpeningCrawl onLoadFinishListener.onLoadFinish(openingCrawl) Every ~5 seconds StarWarsViewModel
- 35. StarWarsActivity
- 36. StarWarsActivity - no leak
- 41. StarWarsViewModel - decide * runOnUiThread - might be avoided using OttoBus event
- 42. CrawlLoader
- 43. So what we got? Clean Debuggable code Decoupled layer Fully testable UI logic Fun :)
- 44. Q?
- 45. Thank you! Leonid Olevsky leonid.olevsky@gmail.com Yonatan Levin levinyon@gmail.com Android Academy
Editor's Notes
- The presenter acts upon the model and the view. It retrieves data from repositories (the model), and formats it for display in the view. The thing is that Data Binding framework will take over the main responsibilities of the Presenter (“acting upon the model and the view”), while the remainder is left to the enhanced Model – the ViewModel (“retreiving data from repositories and formatting”).
- The ViewModel is a standard Java class whose sole responsibility is to represent the data behind a single View. It can merge data from multiple sources (Models) and prepare that data for presentation.
- All the binding and updating of data to the view is done through the Data Binding Framework. The ObservableField class allow the View to react on changes to the model, and the XML references to fields allow the framework to push changes back to the ViewModel when the user acts upon the View. You can also programmatically subscribe to changes in fields. One great advantage of representing the visual state of the View in a standard Java class like this is clear: You can easily unit test the visual behaviour.