How to implement CanSnail for custom views?

[Austin Guest]

Hi all. I'm working on a prototype for a location sharing app for activists.

The first user story is to enable a big red/green "go button" that:

(1) when pressed quickly will flash green add the user's location to a map viewable by all users.

(2) when long-pressed will turn (and stay) green whilst turning on passive-location sharing until long-pressed again (at which point it turns red again)

Cribbing off the excellent work of 47 Degrees, I cobbled together a basic custom CircleView class that works for case (2), but not for case (1). The problem is that case (1) requires that I combine a tweak on the custom view with a standard macroid `delay` snail -- which don't seem to know how to combine together. Specifically...

Given this tweak:

def cvColorChange(color: Int) = Tweak[CircleView] ({ cv ⇒  cv.invalidate(); cv.setColor(color) })

and this effort to snail it: 

goButton <~ cvColor(off) <~
  On.click {
     goButton <~ cvColorChange(off) <~~ delay(100) <~ cvColorChange(on)
  } <~

i get this error message:

Don't know how to snail macroid.Ui[Option[org.tlc.whereat.ui.components.CircleView]] with macroid.Snail[android.view.View]. 
Try importing an instance of CanSnail[macroid.Ui[Option[org.tlc.whereat.ui.components.CircleView]], macroid.Snail[android.view.View], ...]. 

i made a few efforts to implement the implicits involved in CanSnail, but got very lost very quickly. can anyone help?

here are some links for:

* the activity in question

* the layout for the activity

* the custom view for the go button

for those who like long bits of code in emails, here is the same but in the email:

activity:

package org.tlc.whereat.ui.main

import android.app.Activity
import android.os.Bundle
import com.fortysevendeg.macroid.extras.ResourcesExtras._
import macroid.FullDsl._
import macroid.{Contexts, Ui}
import org.tlc.whereat.R
import org.tlc.whereat.ui.components.CircleView._

class MainActivity
  extends Activity
  with Contexts[Activity]
  with MainLayout
  with MainTweaks {

  override def onCreate(savedInstanceState: Bundle) = {

    super.onCreate(savedInstanceState)

    setContentView(layout)

    val off = resGetColor(R.color.go_button_off)
    val on = resGetColor(R.color.go_button_on)

//    runUi {
//      goButton <~ cvColor(off) <~
//        On.click {
//           goButton <~ cvColorChange(off) <~~ delay(100) <~ cvColorChange(on)
//        } <~
//
          /*TODO:
          * The call to `delay(100)` on line 34 above triggers the following error message:
          *
          * Don't know how to snail
          *   macroid.Ui[Option[org.tlc.whereat.ui.components.CircleView]] with macroid.Snail[android.view.View].
          * Try importing an instance of
          *   CanSnail[macroid.Ui[Option[org.tlc.whereat.ui.components.CircleView]], macroid.Snail[android.view.View], ...].
          *
          * How can I fix this?
          * */
        On.longClick {
          toastSharingStatus(goButton, on, off) ~
          ( goButton <~ toggleGoButton(on,off) ) ~
          Ui(true)
        }
    }
  }
}

layout:

package org.tlc.whereat.ui.main

import android.widget.LinearLayout
import macroid.FullDsl._
import macroid.{ActivityContext, AppContext}
import org.tlc.whereat.ui.components.CircleView
import org.tlc.whereat.ui.main.MainStyles._

trait MainLayout {

  var goButton = slot[CircleView]

  def layout(implicit appContext: AppContext, context: ActivityContext) = {

    getUi {
      l[LinearLayout](
        w[CircleView] <~
          wire(goButton) <~ goButtonStyle
      ) <~ goButtonWrapperStyle
    }
  }
}

custom view:

package org.tlc.whereat.ui.components

import android.content.Context
import android.graphics.Paint.Style
import android.graphics.{Canvas, Paint}
import android.util.AttributeSet
import android.view.View
import macroid.FullDsl._
import macroid.{AppContext, Snail, Tweak}

class CircleView(context: Context, attr: AttributeSet, defStyleAttr: Int)
  extends View(context, attr, defStyleAttr) {

  def this(context: Context) = this(context, null, 0)
  def this(context: Context, attr: AttributeSet) = this(context, attr, 0)

  private val paint = { val p = new Paint(); p.setStyle(Style.FILL); p}
  def setColor(color: Int) = paint.setColor(color)
  def getColor: Int = paint.getColor

  override def onDraw(canvas: Canvas): Unit = {
    super.onDraw(canvas)
    canvas.drawCircle(getWidth / 2, getHeight / 2, getWidth / 2, paint)
  }

}

object CircleView {
  type W = CircleView

  def cvColor(color: Int) = Tweak[W] (_.setColor(color))
  def cvColorChange(color: Int) = Tweak[W] ({ cv ⇒  cv.invalidate(); cv.setColor(color) })
  def delayedCvColorChange(color: Int, time: Int): Snail[W] = cvColorChange(color) ++ delay(time)

  def toggleGoButton(on: Int, off: Int) = Tweak[W] { cv ⇒
    cv.invalidate()
    val next = if (cv.getColor == on) off else on
    cv.setColor(next)
  }
  def toastSharingStatus(cv: Option[CircleView], on: Int, off: Int)(implicit appContext: AppContext) = {
    val msg = if (cv.get.getColor == on) "off" else "on"
    toast(s"Location sharing turned $msg.") <~ fry
  }
}

--

Austin Guest
guest....@gmail.com

@aguestuser
831-917-6400

[Nick Stanchenko]

Hi Austin,

Thanks for the detailed post! This is how issues should be reported, period :)

I think you might be missing an implicit scala.concurrent.ExecutionContext in scope. Could you try importing scala.concurrent.ExecutionContext.Implicits.global?

To my defense, the @implicitNotFound message does suggest that at the end of the line :)

Nick