Google Android Study Jam 學習筆記(3)

2022-06-13

1 minute read

學習範圍

單元 3 課程 1

Kotlin 語法

Set

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 val tmp = <list>.toSet()
 val set1 = setOf(1,2,3)
 val set2 = mutableSetOf(3,2,1)

可以用 contains()、intersect()、union()

Map

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 fun main() {
     val peopleAges = mutableMapOf<String, Int>(
         "Fred" to 30,
         "Ann" to 23
     )
     peopleAges.put("Barbara", 42)
     peopleAges["Joe"] = 51
     val filteredNames = peopleAges.filter { it.key.length < 4 }
     println(peopleAges.map { "${it.key} is ${it.value}" }.joinToString(", ") )
     println(peopleAges)
     peopleAges.forEach { print("${it.key} is ${it.value}, ") }
 }

Lambda

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fun main() {
    val triple: (Int) -> Int = { a: Int -> a * 3 }
    println(triple(5))
    val peopleNames = listOf("Fred", "Ann", "Barbara", "Joe")
    println(peopleNames.sortedWith { str1: String, str2: String -> str1.length - str2.length })
    val words = listOf("about", "acute", "awesome", "balloon", "best", "brief", "class", "coffee", "creative")
    val filteredWords = words.filter { it.startsWith("b", ignoreCase = true) }.shuffled().take(2)
}

Android Studio

activity life cycle