KotlinでAndroid開発を気持ちよくしよう

Cybozu Meetup #10 モバイル で発表した内容
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Kotlin はまだ使っていませんか？使っているけれど Java と比べて何が良いかがはっきりしませんか？
実は Java で当たり前な面倒くさい事いっぱいあるけれど Kotlin では当たり前な便利な事がいっぱいあります！
日々の開発が楽になり、「もっと早く Kotlin の事を知っとけばよかった！」と皆様が思うように説明させて頂きます。
Kotlin で Android の開発を気持ちよくしましょう。

Transcript

1. KotlinͰAndroid։ൃ Λؾ࣋ͪΑ͘͠Α͏ Benoît Quenaudon @oldergod
4. Data Class
5. public final class Task { @NonNulla private final String id; @Nullableb private final String title; @Nullablec private final String description; private final boolean completed; public Task(@Nullable String title, @Nullable String description, @NonNull String id, boolean completed) { this.id = id; this.title = title; this.description = description; this.completed = completed; }a }l
6. this.description = description; this.completed = completed; }a @NonNulld public String getId() { return id; }b @Nullablee public String getTitle() { return title; }c @Nullablef public String getTitleForList() { if (!Strings.isNullOrEmpty(title)) { return title; } else { return description; }z }d @Nullableg public String getDescription() { return description; }e public boolean isCompleted() { return completed; }f public boolean isActive() { return !completed; }g public boolean isEmpty() { return Strings.isNullOrEmpty(title) && Strings.isNullOrEmpty(description); }h }l
7. }e public boolean isCompleted() { return completed; }f public boolean isActive() { return !completed; }g public boolean isEmpty() { return Strings.isNullOrEmpty(title) && Strings.isNullOrEmpty(description); }h @Overrideh public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Task task = (Task) o; return Objects.equal(id, task.id) && Objects.equal(title, task.title) && Objects.equal(description, task.description); }i @Overridei public int hashCode() { return Objects.hashCode(id, title, description); }j @Overridej public String toString() { return "Task with title " + title; }k }l
8. public final class Task { @NonNulla private final String id; @Nullableb private final String title; @Nullablec private final String description; private final boolean completed; public Task(@Nullable String title, @Nullable String description, @NonNull String id, boolean completed) { this.id = id; this.title = title; this.description = description; this.completed = completed; }a @NonNulld public String getId() { return id; }b @Nullablee public String getTitle() { return title; }c @Nullablef public String getTitleForList() { if (!Strings.isNullOrEmpty(title)) { return title; } else { return description; } }d @Nullableg public String getDescription() { return description; }e public boolean isCompleted() { return completed; }f public boolean isActive() { return !completed; }g public boolean isEmpty() { return Strings.isNullOrEmpty(title) && Strings.isNullOrEmpty(description); }h @Overrideh public boolean equals(Object o) { if (this == o) return true; if (o == null || getClass() != o.getClass()) return false; Task task = (Task) o; return Objects.equal(id, task.id) && Objects.equal(title, task.title) && Objects.equal(description, task.description); }i @Overridei public int hashCode() { return Objects.hashCode(id, title, description); }j @Overridej public String toString() { return "Task with title " + title; }k }l
9. @Getter @AllArgsConstructor @EqualsAndHashCode @ToString public final class Task { @NonNull private final String id; @Nullable private final String title; @Nullable private final String description; private final boolean completed; @Nullable public String getTitleForList() { if (!Strings.isNullOrEmpty(title)) { return title; } else { return description; } } public boolean isActive() { return !completed; } public boolean isEmpty() { return Strings.isNullOrEmpty(title) && Strings.isNullOrEmpty(description); } } Lombok
10. @AutoValue public abstract class Task { @NonNull abstract String getId(); @Nullable abstract String getTitle(); @Nullable abstract String getDescription(); abstract boolean isCompleted(); public static Task create(@Nullable String title, @Nullable String description, @NonNull String id, boolean completed) { return new AutoValue_Task(id, title, description, completed); } public boolean isActive() { return !isCompleted(); } @Nullable public String getTitleForList() { if (!Strings.isNullOrEmpty(getTitle())) { return getTitle(); } else { return getDescription(); } } public boolean isEmpty() { return Strings.isNullOrEmpty(getTitle()) && Strings.isNullOrEmpty(getDescription()); } } AutoValue
11. data class Task( val id: String, val title: String?, val description: String?, val completed: Boolean ) { val titleForList = if (title.isNotNullNorEmpty()) { title } else { description } val active = !completed val empty = title.isNullOrEmpty() && description.isNullOrEmpty() } Kotlin
12. data class Task( val id: String, val title: String?, val description: String?, var completed: Boolean )
13. data class Task( val id: String, val title: String?, val description: String?, var completed: Boolean ) • constructor • getters • setters (var only) • toString • equals & hashCode • copy • componentN
14. data class Task( val id: String, val title: String?, val description: String?, var completed: Boolean ) • constructor • getters • setters (var only) • toString • equals & hashCode • copy • componentN
15. data class Task( val id: String, val title: String?, val description: String?, var completed: Boolean ) • constructor • getters • setters (var only) • toString • equals & hashCode • copy • componentN
16. data class Task( val id: String, val title: String?, val description: String?, var completed: Boolean ) • constructor • getters • setters (var only) • toString • equals & hashCode • copy • componentN
17. data class Task( val id: String, val title: String?, val description: String?, var completed: Boolean ) • constructor • getters • setters (var only) • toString • equals & hashCode • copy • componentN
18. data class Task( val id: String, val title: String?, val description: String?, var completed: Boolean ) • constructor • getters • setters (var only) • toString • equals & hashCode • copy • componentN
19. data class Task( val id: String, val title: String?, val description: String?, var completed: Boolean ) • constructor • getters • setters (var only) • toString • equals & hashCode • copy • componentN
20. Sealed Class
21. sealed class ViewHolder { data class HeaderViewHolder(val text: String) : ViewHolder() class ItemViewHolder(val data: String) : ViewHolder() object LoadingViewHolder : ViewHolder() }z
22. sealed class ViewHolder { data class HeaderViewHolder(val text: String) : ViewHolder() class ItemViewHolder(val data: String) : ViewHolder() object LoadingViewHolder : ViewHolder() }z
23. sealed class ViewHolder { data class HeaderViewHolder(val text: String) : ViewHolder() class ItemViewHolder(val data: String) : ViewHolder() object LoadingViewHolder : ViewHolder() }z
24. sealed class ViewHolder { data class HeaderViewHolder(val text: String) : ViewHolder() class ItemViewHolder(val data: String) : ViewHolder() object LoadingViewHolder : ViewHolder() }z
25. sealed class ViewHolder { data class HeaderViewHolder(val text: String) : ViewHolder() class ItemViewHolder(val data: String) : ViewHolder() object LoadingViewHolder : ViewHolder() }z
26. sealed class ViewHolder(val root: View) : RecyclerView.ViewHolder(view) { class HeaderViewHolder(root: View) : ViewHolder(root) class ItemViewHolder(root: View) : ViewHolder(root) class LoadingViewHolder(root: View) : ViewHolder(root) }z
27. sealed class ViewHolder(val root: View) : RecyclerView.ViewHolder(view) { class HeaderViewHolder(root: View) : ViewHolder(root) class ItemViewHolder(root: View) : ViewHolder(root) class LoadingViewHolder(root: View) : ViewHolder(root) }z
28. sealed class ViewHolder(val root: View) : RecyclerView.ViewHolder(view) { class HeaderViewHolder(root: View) : ViewHolder(root) class ItemViewHolder(root: View) : ViewHolder(root) class LoadingViewHolder(root: View) : ViewHolder(root) }z
29. override fun onBindViewHolder(holder: ViewHolder, position: Int) { return when (holder) { is HeaderViewHolder -> { /*****/ } is ItemViewHolder -> { /*****/ } is LoadingViewHolder -> { /*****/ } } }
30. sealed class ViewHolder(val root: View) : RecyclerView.ViewHolder(view) { class HeaderViewHolder(root: View) : ViewHolder(root) class ItemViewHolder(root: View) : ViewHolder(root) class LoadingViewHolder(root: View) : ViewHolder(root) }d
31. sealed class ViewHolder(val root: View) : RecyclerView.ViewHolder(view) { class HeaderViewHolder(root: View) : ViewHolder(root) class ItemViewHolder(root: View) : ViewHolder(root) class LoadingViewHolder(root: View) : ViewHolder(root) class FooterViewHolder(root: View) : ViewHolder(root) }d
32. override fun onBindViewHolder(holder: ViewHolder, position: Int) { return when (holder) { is HeaderViewHolder -> { /*****/ } is ItemViewHolder -> { /*****/ } is LoadingViewHolder -> { /*****/ } } }
33. override fun onBindViewHolder(holder: ViewHolder, position: Int) { return when (holder) { is HeaderViewHolder -> { /*****/ } is ItemViewHolder -> { /*****/ } is LoadingViewHolder -> { /*****/ } }z }d
34. override fun onBindViewHolder(holder: ViewHolder, position: Int) { return when (holder) { is HeaderViewHolder -> { /*****/ } is ItemViewHolder -> { /*****/ } is LoadingViewHolder -> { /*****/ } is FooterViewHolder -> { /*****/ }f }z }d
35. override fun onBindViewHolder(holder: ViewHolder, position: Int) { return when (holder) { is HeaderViewHolder -> { /*****/ } is ItemViewHolder -> { /*****/ } is LoadingViewHolder -> { /*****/ } is FooterViewHolder -> { /*****/ }f }z }d
36. override fun onBindViewHolder(holder: ViewHolder, position: Int) { return when (holder) { is HeaderViewHolder -> { /*****/ } is ItemViewHolder -> { /*****/ } is LoadingViewHolder -> { /*****/ } is FooterViewHolder -> { val footerVH = holder as FooterViewHolder footerVH.stuff() }f }z }d
37. override fun onBindViewHolder(holder: ViewHolder, position: Int) { return when (holder) { is HeaderViewHolder -> { /*****/ } is ItemViewHolder -> { /*****/ } is LoadingViewHolder -> { /*****/ } is FooterViewHolder -> { holder.stuff() }f }z }d
38. override fun onBindViewHolder(holder: ViewHolder, position: Int) { return when (holder) { is HeaderViewHolder -> { /*****/ } is ItemViewHolder -> { /*****/ } is LoadingViewHolder -> { /*****/ } is FooterViewHolder -> { /*****/ }f }z }d
39. Collections API
40. List<Action> actions; List<Task> tasks = new ArrayList<>(actions.size()); for (Action action : actions) { Task task = new Task(action.title(), action.description()); tasks.add(task); }
41. List<Action> actions; List<Task> tasks = new ArrayList<>(actions.size()); for (Action action : actions) { Task task = new Task(action.title(), action.description()); tasks.add(task); }
42. List<Action> actions; List<Task> tasks = new ArrayList<>(actions.size()); for (Action action : actions) { Task task = new Task(action.title(), action.description()); tasks.add(task); }
43. List<Action> actions; List<Task> tasks = new ArrayList<>(actions.size()); for (Action action : actions) { Task task = new Task(action.title(), action.description()); tasks.add(task); }
44. List<Action> actions; List<Task> tasks = new ArrayList<>(actions.size()); for (Action action : actions) { Task task = new Task(action.title(), action.description()); tasks.add(task); }
45. List<Action> actions; List<Task> tasks = new ArrayList<>(actions.size()); for (Action action : actions) { Task task = new Task(action.title(), action.description()); tasks.add(task); }
46. valaactions:zList<Action> valbtasksz= ArrayList(actions.size) for (action in actions) { valctask = Task(action.title, action.description) tasks.add(task) }
47. valaactions:zList<Action> valbtasksz= actions.map { Task(it.title, it.description) }
48. • map() • filter() • find() • distinct() • any() • groupBy() • zip() • …
49. • map() • filter() • find() • distinct() • any() • groupBy() • zip() • … val list: List<Int> = listOf(1, 2, 3) val map: Map<String, Int> = mapOf("a" to 1, "b" to 2) val set: Set<String> = setOf("a", "b", “c")
50. • map() • filter() • find() • distinct() • any() • groupBy() • zip() • … val list: List<Int> = listOf(1, 2, 3) val map: Map<String, Int> = mapOf("a" to 1, "b" to 2) val set: Set<String> = setOf("a", "b", “c")
51. Lazy Delegate
52. private lateinit var viewModel: TaskViewModel private lateinit var taskId: String override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) viewModel = ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) taskId = arguments?.getString(ARGUMENT_EDIT_TASK_ID) }c
53. private lateinit var viewModel: TaskViewModel private lateinit var taskId: String override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) viewModel = ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) taskId = arguments?.getString(ARGUMENT_EDIT_TASK_ID) }c
54. private lateinit var viewModel: TaskViewModel private lateinit var taskId: String override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) viewModel = ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) taskId = arguments?.getString(ARGUMENT_EDIT_TASK_ID) }c
55. private lateinit var viewModel: TaskViewModel private lateinit var taskId: String override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) viewModel = ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) taskId = arguments?.getString(ARGUMENT_EDIT_TASK_ID) }c
56. private val viewModel: TaskViewModel by lazy { ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) }x private val taskId: String by lazy { arguments?.getString(ARGUMENT_EDIT_TASK_ID) }y override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) }c
57. private val viewModel: TaskViewModel by lazy { ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) }x private val taskId: String by lazy { arguments?.getString(ARGUMENT_EDIT_TASK_ID) }y override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) }c
58. private val viewModel: TaskViewModel by lazy { ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) }x private val taskId: String by lazy { arguments?.getString(ARGUMENT_EDIT_TASK_ID) }y override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) }c
59. private val viewModel: TaskViewModel by lazy { ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) }x private val taskId: String by lazy { arguments?.getString(ARGUMENT_EDIT_TASK_ID) }y override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) }c
60. private val viewModel: TaskViewModel by lazy { ViewModelProviders .of(this, ViewModelFactory()) .get(TaskViewModel::class.java) }x private val taskId: String by lazy { arguments?.getString(ARGUMENT_EDIT_TASK_ID) }y override fun onViewCreated(view: View, savedInstanceState: Bundle?) { super.onViewCreated(view, savedInstanceState) }
61. Operators
62. class TaskDetailFragment(val taskId: String) : Fragment()
63. class TaskDetailFragment(val taskId: String) : Fragment() val fragment = TaskDetailFragment(taskId)
64. class TaskDetailFragment(val taskId: String) : Fragment() val fragment = TaskDetailFragment(taskId)
65. class TaskDetailFragment(val taskId: String) : Fragment() val fragment = TaskDetailFragment(taskId)
66. val fragment = TaskDetailFragment()
67. val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId)
68. val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle
69. class TaskDetailFragment : Fragment() { companion object { fun newInstance(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c
70. class TaskDetailFragment : Fragment() { companion object { fun newInstance(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment.newInstance(taskId)
71. class TaskDetailFragment : Fragment() { companion object { fun newInstance(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment.newInstance(taskId)
72. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment.newInstance(taskId)
73. class Foo() { operator fun invoke(): String { return "invoked !" } } fun main(args: Array<String>) { val foo: Foo = Foo() println(foo()) // invoked ! }
74. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment.newInstance(taskId)
75. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment.newInstance(taskId)
76. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment(taskId)
77. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment(taskId)
78. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle() bundle.putString(ARGUMENT_TASK_ID, taskId) fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment(taskId)
79. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle().apply { this.putString(ARGUMENT_TASK_ID, taskId) }p fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment(taskId)
80. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() val bundle = Bundle().apply { putString(ARGUMENT_TASK_ID, taskId) }p fragment.arguments = bundle return fragment }a }b }c val fragment = TaskDetailFragment(taskId)
81. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment() fragment.arguments = Bundle().apply { putString(ARGUMENT_TASK_ID, taskId) }p return fragment }a }b }c val fragment = TaskDetailFragment(taskId)
82. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { val fragment = TaskDetailFragment().apply { arguments = Bundle().apply { putString(ARGUMENT_TASK_ID, taskId) }p }p return fragment }a }b }c val fragment = TaskDetailFragment(taskId)
83. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String): TaskDetailFragment { return TaskDetailFragment().apply { arguments = Bundle().apply { putString(ARGUMENT_TASK_ID, taskId) }p }p }a }b }c val fragment = TaskDetailFragment(taskId)
84. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String) = TaskDetailFragment().apply { arguments = Bundle().apply { putString(ARGUMENT_TASK_ID, taskId) }p }p }a }b }c val fragment = TaskDetailFragment(taskId)
85. class TaskDetailFragment : Fragment() { companion object { operator fun invoke(taskId: String) = TaskDetailFragment().apply { arguments = Bundle().apply { putString(ARGUMENT_TASK_ID, taskId) }p }p }a }b }c val fragment = TaskDetailFragment(taskId)
86. Fin Benoît Quenaudon @oldergod