I don't understand what is wrong - kotlin

Question

I am new in kotlin and i don't understand what is wrong, when i do a "CLICK" in the imageView (val_jugadorX.alpha = 0.5f) i can't unselect it again (val_jugadorX.alpha = 1f)
fun comprobarSeleccion(val_jugadorX: ImageView): Boolean{
// si el boleano es false, no está seleccionado
// si el boleano es verdadero, está seleccionado
var devolver: Boolean = false
if (val_jugadorX.alpha == 1f){
val_jugadorX.setOnClickListener {
val_jugadorX.alpha = 0.5f
println("Ahora está seleccionado")
devolver = true
}
}else if(val_jugadorX.alpha== 0.5f) {
val_jugadorX.setOnClickListener{
val_jugadorX.alpha = 1f
println("Ahora no está selccio")
devolver = false
}
}
return devolver
}

Answer 1

You're setting a click listener based on the ImageView's current alpha, and that click listener changes the alpha. But it doesn't call comprobarSeleccion again to set a new click listener based on its new alpha. You probably want to do something like this:
fun comprobarSeleccion(val_jugadorX: ImageView): Boolean{
// si el boleano es false, no está seleccionado
// si el boleano es verdadero, está seleccionado
var devolver: Boolean = false
if (val_jugadorX.alpha == 1f){
val_jugadorX.setOnClickListener {
val_jugadorX.alpha = 0.5f
println("Ahora está seleccionado")
devolver = true
// now the alpha has changed, we need a new click listener
comprobarSeleccion(val_jugadorX)
}
} ...
}
Although something like this might be better (maybe set up during initialisation):
someImageView.setOnClickListener {
with(someImageView) {
val selected = alpha == 1f
// update display
alpha = if (selected) 0.5f else 1f
// handle the selection change event
setSelected(selected)
}
}
That way you just set a click listener once, and it handles things depending on its current state. By having a separate setSelected function, you can tell another part of the app that this selection state has changed:
var devolver = false
fun setSelected(selected: Boolean) {
println(if (selected) "Ahora está seleccionado" else "Ahora no está selccio")
devolver = selected
// any other stuff that needs to happen because of the selection change
}
That fixes your other problem - in your example, devolver is a local variable inside comprobarSeleccion. You set it to false, then return it (i.e. return false). If a click listener changes it later, nothing can access it. Next time you call comprobarSeleccion you get a new devolver set to false again.
By making it a top-level variable, your setSelected function can change it (or your click listener can if you want) and everything else can see its current value.