defHLT / kotlin-anko-view-controllers

kotlin-anko-view-controllers

This package is Android-specific, and therefore is not cross-platform.

This package greatly simplifies creating different screens in an app by providing an alternative to Activity called ViewController, which has the following differences:

• Lightweight - ViewController is simply an interface with one primary function - make(activity:VCActivity):View, which builds the views and returns the heirarchy.
• Data retention - ViewControllers are built to hold information that should be displayed between view recreations by being stored statically. This completely removes the need for storing things using Bundle and Parcelable, which are both time consuming to implement and reduce type safety.
• Data passing - ViewControllers are built to allow easy sending of information between different views, allowing you to pass information through the constructor. This completely removes the need for passing things using Bundle and Parcelable, which are both time consuming to implement and reduce type safety.

Example Project

An example project that uses components from this library as well as some sibling libraries:

kotlin-components-starter

Example Top-Level Activity

class MainActivity : VCActivity() {

    companion object {
         // This creates a new stack of view controllers.
        val stack = VCStack().apply{
            //Push an initial view controller onto the stack.
            //This view controller is defined below.
            push(StackDemoVC(this))
        }
        
        //ContainerVC is a view controller that displays a container of other view controllers.
        //The most important type of container (and most common) is VCStack.
        val mainVC = ContainerVC(stack) 
    }

    override val viewController: ViewController
        get() = mainVC
}

Example View Controller

//AnkoViewController is a view controller whose view is created using Anko.  This is the most common class to extend from.
//Notice how we are passing in information through our constructor.
class StackDemoVC(val stack: VCStack, val depth: Int = 1) : AnkoViewController() {

    //This function simply defines a title for this view.  You can make other things use this later.
    override fun getTitle(resources: Resources): String {
        return "Stack Demo ($depth)"
    }

    //This function actually creates the view.
    override fun createView(ui: AnkoContext<VCActivity>): View = ui.verticalLayout {
        gravity = Gravity.CENTER

        textView("This view controller has a depth of $depth.") {
            //I typically make a separate file called "Style.kt" which defines extension functions for each view
            //named things like "styleDefault" to handle styling.
            styleDefault()
        }

        button("Go deeper") {
            styleDefault()
            onClick {
                //This pushes a new view controller onto the stack.
                stack.push(StackDemoVC(stack, depth + 1))
            }
        }

        button("Go back") {
            styleDefault()
            onClick {
                //This removes a view controller from the stack, going back to the previous view controller.
                stack.pop()
            }
        }
    }
}