Google Android Study Jam 學習筆記(2)

2022-06-11

1 minute read

學習範圍

單元 2 課程 3

Kotlin 語法

list

宣告

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val numbers: List<Int> = listOf(1, 2, 3, 4, 5, 6)

其他

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println("List: $numbers") // = println("List: " + numbers)
println("Size: ${numbers.size}")
println("First element: ${numbers[0]}")
println("First: ${numbers.first()}")
println("Last: ${numbers.last()}")
println("Contains 4? ${numbers.contains(4)}") // true
println("Contains 7? ${numbers.contains(7)}") // false
println("Reversed list: ${colors.reversed()}")
println("Sorted list: ${colors.sorted()}")

mutablelist

宣告

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val entrees = mutableListOf<String>() // val entrees: MutableList<String> = mutableListOf()

其他

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println("Add noodles: ${entrees.add("noodles")}")
val moreItems = listOf("ravioli", "lasagna", "fettuccine")
println("Add list: ${entrees.addAll(moreItems)}") // "Add list: true"
println("Remove spaghetti: ${entrees.remove("spaghetti")}")
println("Remove first element: ${entrees.removeAt(0)}")
entrees.clear()
println("Empty? ${entrees.isEmpty()}")

while

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val guestsPerFamily = listOf(2, 4, 1, 3)
var totalGuests = 0
var index = 0
while (index < guestsPerFamily.size) {
    totalGuests += guestsPerFamily[index]
    index++
}
println("Total Guest Count: $totalGuests")

for

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for (name in names) println(name)
for (item in 5 downTo 1) print(item)
for (item in 3..6 step 2) print(item)

vararg
將類型相同、數量可變的引數傳遞給函式或建構函式

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// 只能將一個參數標示為 vararg，且通常是清單中的最後一個參數。
class Vegetables(vararg val toppings: String) : Item("Vegetables", 5) {

Android Studio

RecycleView
MaterialCardView

其他

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