10 Extension Functions of Kotlin in Android Development

10 Extension Functions of Kotlin in Android Development

Transcript

1. 10 Extension Functions of Kotlin in Android Development @magiepooh
2. About me @magiepooh @magie_pooh Takuma Fujita
3. Company CyberAgent, Inc.
4. 10 Extension Functions of Kotlin in Android Development @magiepooh
5. What’s Kotlin?
6. Kotlin • By JetBrains • Lambdas • Nullable(NonNull) • Higher-Order Functions (Stream) • Extension Functions
7. Kotlin • By JetBrains • Lambdas -> Retrolambda • Nullable(NonNull) • Higher-Order Functions (Stream) • Extension Functions
8. Kotlin • By JetBrains • Lambdas -> Retrolambda • Nullable(NonNull) -> Optional • Higher-Order Functions (Stream) • Extension Functions
9. Kotlin • By JetBrains • Lambdas -> Retrolambda • Nullable(NonNull) -> Optional • Higher-Order Functions (Stream) -> RxJava • Extension Functions
10. Kotlin • By JetBrains • Lambdas -> Retrolambda • Nullable(NonNull) -> Optional • Higher-Order Functions (Stream) -> RxJava • Extension Functions
11. Functions in Kotlin
12. Functions in Kotlin fun sum(a: Int, b: Int): Int {
 return a + b
 }
13. Functions in Kotlin fun sum(a: Int, b: Int): Int {
 return a + b
 }
14. Functions in Kotlin fun sum(a: Int, b: Int): Int {
 return a + b
 }
15. Functions in Kotlin fun sum(a: Int, b: Int): Int {
 return a + b
 }
16. Functions in Kotlin fun sum(a: Int, b: Int): Int = a + b
17. Functions in Kotlin fun sum(a: Int, b: Int): Int = a + b
18. Functions in Kotlin fun sum(a: Int, b: Int) = a + b
19. Extension Functions
20. Extension Functions static void toast(Context context, String text) { Toast.makeText(context, text, Toast.LENGTH_SHORT).show(); }
21. Extension Functions void toast(Context context, String text) { Toast.makeText(context, text, Toast.LENGTH_SHORT).show(); }
22. Extension Functions fun toast(Context context, String text) { Toast.makeText(context, text, Toast.LENGTH_SHORT).show(); }
23. Extension Functions fun toast(Context context, String text) { Toast.makeText(context, text, Toast.LENGTH_SHORT).show(); }
24. Extension Functions fun toast(context: Context, text: String) { Toast.makeText(context, text, Toast.LENGTH_SHORT).show() }
25. fun Activity.toast(context: Context, text: String) { Toast.makeText(context, text, Toast.LENGTH_SHORT).show() } Extension Functions
26. fun Activity.toast(context: Context, text: String) { Toast.makeText(context, text, Toast.LENGTH_SHORT).show() } Extension Functions
27. fun Activity.toast(context: Context, text: String) { Toast.makeText(this, text, Toast.LENGTH_SHORT).show() } Extension Functions
28. fun Activity.toast(context: Context, text: String) { Toast.makeText(this, text, Toast.LENGTH_SHORT).show() } Extension Functions
29. fun Activity.toast(text: String) { Toast.makeText(this, text, Toast.LENGTH_SHORT).show() } Extension Functions
30. fun Activity.toast(text: String) { Toast.makeText(this, text, Toast.LENGTH_SHORT).show() } override fun onCreate(savedInstanceState : Bundle?) { toast(“Hello, Toast!”) } Extension Functions
31. fun Activity.toast(text: String) = Toast.makeText(this, text, Toast.LENGTH_SHORT).show() override fun onCreate(savedInstanceState : Bundle?) { toast(“Hello, Toast!”) } Extension Functions
32. Some Extension Functions
33. toVisible
34. toVisible fun View.toVisible() { visibility = View.VISIBLE } textView.toVisible()
35. toVisible fun View.toVisible() { visibility = View.VISIBLE } textView.toVisible() textView.toGone() textView.isVisible() textView.isGone()
36. setFragment
37. setFragment fun FragmentActivity.setFragment(fragment: Fragment, containerId: Int) = supportFragmentManager .beginTransaction() .add(containerId, fragment) .commit()
38. setFragment fun FragmentActivity.setFragment(fragment: Fragment, containerId: Int) = supportFragmentManager .beginTransaction() .add(containerId, fragment) .commit() setFragment(MainFragment.newInstance(), android.R.id.content)
39. setFragment fun FragmentActivity.setFragment(fragment: Fragment, containerId: Int) = supportFragmentManager .beginTransaction() .add(containerId, fragment) .commit() setFragment(MainFragment.newInstance(), android.R.id.content)
40. setFragment fun FragmentActivity.setFragment(fragment: Fragment, containerId: Int = android.R.id.content) = supportFragmentManager .beginTransaction() .add(containerId, fragment) .commit() setFragment(MainFragment.newInstance(), android.R.id.content)
41. setFragment fun FragmentActivity.setFragment(fragment: Fragment, containerId: Int = android.R.id.content) = supportFragmentManager .beginTransaction() .add(containerId, fragment) .commit() setFragment(MainFragment.newInstance())
42. setFragment fun FragmentActivity.setFragment(fragment: Fragment, containerId: Int = android.R.id.content) = supportFragmentManager .beginTransaction() .add(containerId, fragment) .commit() setFragment(MainFragment.newInstance()) setFragment(MainFragment.newInstance(), R.id.my_content)
43. getString
44. getString(Java) getActivity().getResources().getString(resId)
45. getString fun Fragment.getString(@StringRes resId: Int) = getActivity().getResources().getString(resId)
46. getString fun Fragment.getString(@StringRes resId: Int) = activity.resources.getString(resId)
47. let
48. let public inline fun <T, R> T.let(f: (T) -> R): R = f(this)
49. let someObject?.let { // `it` is non-null }
50. Compat
51. isAttachedToWindow
52. isAttachedToWindow fun View.isAttachedToWindowCompat () = if (Build.VERSION.SDK_INT < 19) { ViewCompat.isAttachedToWindow(this) } else { isAttachedToWindow() }
53. Cast
54. WindowManager
55. WindowManager(Java) WindowManager windowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE)
56. WindowManager fun Context.getWindowManager() = getSystemService(Context.WINDOW_SERVICE) as WindowManager
57. WindowManager fun Context.getWindowManager() = getSystemService(Context.WINDOW_SERVICE) as WindowManager
58. WindowManager fun Context.getWindowManager() = getSystemService(Context.WINDOW_SERVICE) as WindowManager val windowManager = getWindowManager() val display = windowManager.getDefaultDisplay() val width = display.width val height = display.height
59. Extension Properties
60. WindowManager fun Context.getWindowManager() = getSystemService(Context.WINDOW_SERVICE) as WindowManager val windowManager = getWindowManager() val display = windowManager.getDefaultDisplay() val width = display.width val height = display.height
61. WindowManager val Context.windowManager = get() = getSystemService(Context.WINDOW_SERVICE) as WindowManager val windowManager = getWindowManager() val display = windowManager.getDefaultDisplay() val width = display.width val height = display.height
62. WindowManager val Context.windowManager = get() = getSystemService(Context.WINDOW_SERVICE) as WindowManager val display = windowManager.getDefaultDisplay() val width = display.width val height = display.height
63. Extends Library
64. Glide Extension http://www.example.com/12345?width=300&height=300
65. Glide Extension http://www.example.com/12345?width=300&height=300
66. Glide Extension fun RequestManager.loadOptimize(url: String?, width: Int, height: Int): DrawableTypeRequest<String> = load(url?.let { "$it?width=$width&height=$height" })
67. Glide Extension fun RequestManager.loadOptimize(url: String?, width: Int, height: Int): DrawableTypeRequest<String> = load(url?.let { "$it?width=$width&height=$height" })
68. Glide Extension fun RequestManager.loadOptimize(url: String?, width: Int, height: Int): DrawableTypeRequest<String> = load(url?.let { "$it?width=$width&height=$height" })
69. Glide Extension fun RequestManager.loadOptimize(url: String?, width: Int, height: Int): DrawableTypeRequest<String> = load(url?.let { "$it?width=$width&height=$height" }) Glide.with(context) .loadOptimize(url, 300, 300) .into(imageView)
70. Listener
71. addOnPageChangeListener
72. ViewPager# OnPageChangeListener(Java) pager.addOnPageChangeListener(new OnPageChangeListener() { @Override public void onPageSelected(int position) { // no op } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { // no op } @Override public void onPageScrollStateChanged(int state) { onStateChange(state); } });
73. ViewPager# OnPageChangeListener(Java) pager.addOnPageChangeListener(new OnPageChangeListener() { @Override public void onPageSelected(int position) { // no op } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { // no op } @Override public void onPageScrollStateChanged(int state) { onStateChange(state); } });
74. ViewPager# OnPageChangeListener(Java) pager.addOnPageChangeListener(new OnPageChangeListener() { @Override public void onPageSelected(int position) { // no op } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { // no op } @Override public void onPageScrollStateChanged(int state) { onStateChange(state); } });
75. fun ViewPager.addOnPageChangeListener( onPageScrolled: (position: Int, positionOffset: Float, positionOffsetPixels: Int) -> Unit = { position, positionOffset, positionOffsetPixels -> }, onPageScrollStateChanged: (state: Int) -> Unit = {}, onPageSelected: (position: Int) -> Unit = {} ) = addOnPageChangeListener(object : ViewPager.OnPageChangeListener { override fun onPageScrolled(position: Int, positionOffset: Float, positionOffsetPixels: Int) { onPageScrolled(position, positionOffset, positionOffsetPixels) } override fun onPageScrollStateChanged(state: Int) { onPageScrollStateChanged(state) } override fun onPageSelected(position: Int) { onPageSelected(position) } })
76. OnPageChangeListener(Java) pager.addOnPageChangeListener(new OnPageChangeListener() { @Override public void onPageSelected(int position) { // no op } @Override public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) { // no op } @Override public void onPageScrollStateChanged(int state) { onStateChange(state); } });
77. Extends addOnPageChangeListener pager.addOnPageChangeListener(onPageScrollStateChanged = { onStateChange(state) })
78. Extends addOnPageChangeListener pager.addOnPageChangeListener(onPageScrollStateChanged = { onStateChange(state) })
79. Animator
80. Animator(Java) anim.addListener(new AnimatorListener() { ... @Override public void onAnimationEnd(Animator animation) { animDrawable.stop() } ... }); anim.setDuration(300) .start();
81. Animator fun Animator.addListener( onAnimationStart: (Animator) -> Unit = {}, onAnimationEnd: (Animator) -> Unit = {}, onAnimationCancel: (Animator) -> Unit = {}, onAnimationRepeat: (Animator) -> Unit = {}): Animator { addListener(object : Animator.AnimatorListener { override fun onAnimationStart(animation: Animator) { onAnimationStart(animation) } // ….. }) return this }
82. Animator fun Animator.addListener( onAnimationStart: (Animator) -> Unit = {}, onAnimationEnd: (Animator) -> Unit = {}, onAnimationCancel: (Animator) -> Unit = {}, onAnimationRepeat: (Animator) -> Unit = {}): Animator { addListener(object : Animator.AnimatorListener { override fun onAnimationStart(animation: Animator) { onAnimationStart(animation) } // ….. }) return this }
83. Animator fun Animator.addListener( onAnimationStart: (Animator) -> Unit = {}, onAnimationEnd: (Animator) -> Unit = {}, onAnimationCancel: (Animator) -> Unit = {}, onAnimationRepeat: (Animator) -> Unit = {}): Animator { addListener(object : Animator.AnimatorListener { override fun onAnimationStart(animation: Animator) { onAnimationStart(animation) } // ….. }) return this }
84. Animator anim .addListener(onAnimationEnd = { animDrawable.stop() }) .setDuration(300) .start();
85. Animator anim .addListener(onAnimationEnd = { animDrawable.stop() }) .setDuration(300) .start();
86. Thank you !!