Using Kotlin in Android

Kotlin examples for study group in Taiwan Kotlin User Group

Transcript

1. Using Kotlin in Android Ivan W.
2. Outline • Null Safety • Data Class • Default Argument / Implementation 2
3. Null Safety • Eliminate the danger of null references from code • Nullable types and Non-Null Types var a: String = "abc" a = null // compilation error var b: String? = "abc" b = null // ok 3 Nullable types Non-Null types
4. Example 1 4 Bundle args = getArguments(); if (args != null) { Bundle data = args.getBundle(KEY_DATA); if (data != null) { Log.d(TAG, data.getString(KEY_NAME)); } } Java
5. Example 1 5 Bundle args = getArguments(); if (args != null) { Bundle data = args.getBundle(KEY_DATA); if (data != null) { Log.d(TAG, data.getString(KEY_NAME)); } } Log.d(TAG, arguments?.getBundle(KEY_DATA)?.getString(KEY_NAME)) Java Kotlin
6. Data Class • It automatically generates ◦ equals() / hashCode() ◦ getters and setters ◦ toString() ◦ copy()
7. Example 2 7 Java Kotlin See example See example
8. Default Argument / Implementation 8 • Java overloads can be replaced with one function in Kotlin
9. Example 3 9 private void sendInfo(String content, long Time, String tag) { /* ... */ } private void sendInfo(String content, long Time) { /* ... */ } private void sendInfo(String content, String tag) { /* ... */ } private void sendInfo(String content) { /* ... */ } Java
10. Example 3 10 private fun sendInfo( content: String, time: Long = Date().time, tag: String = TAG ) { … } sendInfo("content", time = Date().time) Kotlin
11. Example 4 11 Java Kotlin See example See example
12. Thank you! 12