「Android/kotlin/配列」の版間の差分
提供: 初心者エンジニアの簡易メモ
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| (同じ利用者による、間の13版が非表示) | |||
| 行1: | 行1: | ||
| − | == | + | ==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=== | ||
<pre> | <pre> | ||
| − | + | val names:ArrayList<String> = arrayListOf("taro", "jiro") | |
if (names.isNotEmpty()) { | if (names.isNotEmpty()) { | ||
for (name: String in names) { | for (name: String in names) { | ||
| − | Log.d("test", "name= | + | Log.d("test", "name=$name") |
} | } | ||
| + | } | ||
| + | </pre> | ||
| + | |||
| + | or | ||
| + | |||
| + | ===foreach=== | ||
| + | <pre> | ||
| + | names.forEach { name -> | ||
| + | Log.d("test", "name=$name") | ||
| + | } | ||
| + | </pre> | ||
| + | |||
| + | itを使う場合 | ||
| + | <pre> | ||
| + | names.forEach { | ||
| + | Log.d("test", "name=$it") | ||
} | } | ||
</pre> | </pre> | ||
| 行22: | 行40: | ||
user2.name = "jiro" | user2.name = "jiro" | ||
var users: ArrayList<User> = arrayListOf(user, user2) | var users: ArrayList<User> = arrayListOf(user, user2) | ||
| + | var username = users.firstOrNull { it.name.contains("taro") }?.name ?: "" // taro | ||
for (user: User in users) { | for (user: User in users) { | ||
Log.i("test", "user.name=" + user.name) | Log.i("test", "user.name=" + user.name) | ||
} | } | ||
| − | |||
</pre> | </pre> | ||
| + | |||
| + | ==配列プロパティ条件一致で更新== | ||
| + | <pre> | ||
| + | var user = User() | ||
| + | user.name = "taro" | ||
| + | var user2 = User() | ||
| + | user2.name = "jiro" | ||
| + | var users: ArrayList<User> = arrayListOf(user, user2) | ||
| + | users.firstOrNull {it.name == "taro"}?.name = "saburo" // taroをsaburoへ | ||
| + | for (user: User in users) { | ||
| + | Log.i("test", "user.name=" + user.name) | ||
| + | } | ||
| + | </pre> | ||
| + | |||
| + | ==mutableリストに文字列追加== | ||
| + | val names = mutableListOf<String>() | ||
| + | for (i in 1..10000) names.add("name" + i) | ||
| + | |||
| + | ==配列をnullでいれて、空の配列用意== | ||
| + | private var names: ArrayList<string?>? = null | ||
| + | names = ArrayList() | ||
| + | names!!.add("taro") // データ挿入 | ||
2021年2月10日 (水) 18:01時点における最新版
目次
配列
自分はforeachはbreakなどが使えないので、for-inのほうが好き
for-in
val names:ArrayList<String> = arrayListOf("taro", "jiro")
if (names.isNotEmpty()) {
for (name: String in names) {
Log.d("test", "name=$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
