Android/kotlin/配列

配列

自分はforeachはbreakなどが使えないので、for-inのほうが好き

for-in

val names:ArrayList<String> = arrayListOf("taro", "jiro")
if (names.isNotEmpty()) {
    for (name: String in names) {
        Log.d("test", "name=$name")
    }
}

or

foreach

names.forEach { name ->
     Log.d("test", "name=$name")
}

itを使う場合

names.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)

配列をnullでいれて、空の配列用意

private var names: ArrayList<string?>? = null
names = ArrayList()
names!!.add("taro") // データ挿入