「Android/kotlin/配列」の版間の差分

2020年10月1日 (木) 16:45時点における版

配列

for-in

var names:Array<String>
if (names.isNotEmpty()) {
    for (name: String in names) {
        Log.d("test", "name=" + name)
    }
}

foreach

names:Array.forEach {
        Log.d("test", "name=" + it)
}

配列プロパティ値取得

User.kt

class User {
    var name: String = ""
}

var user = User()
user.name = "taro"
var user2 = User()
user2.name = "jiro"
var users: ArrayList<User> = arrayListOf(user, user2)
var username = users.firstOrNull { it.name.contains("taro") }?.name ?: "" // taro
for (user: User in users) {
    Log.i("test", "user.name=" + user.name)
}

配列プロパティ条件一致で更新

var user = User()
user.name = "taro"
var user2 = User()
user2.name = "jiro"
var users: ArrayList<User> = arrayListOf(user, user2)
users.firstOrNull {it.name == "taro"}?.name = "saburo" // taroをsaburoへ
for (user: User in users) {
    Log.i("test", "user.name=" + user.name)
}

mutableリストに文字列追加

val names  = mutableListOf<String>()
for (i in 1..10000) names.add("name" + i)