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@MOLSJEROEN GETTING THE MOST OUT OF ANDROID KTX

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@MOLSJEROEN

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@MOLSJEROEN WHAT AND WHY CRASH COURSE WRITE YOUR OWN DISCOVER MORE

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WHAT AND WHY

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@MOLSJEROEN ANDROID CAN SOMETIMES BE TEDIOUS view.addOnLayoutChangeListener( object : View.OnLayoutChangeListener { override fun onLayoutChange( view: View, left: Int, top: Int, right: Int, bottom: Int, oldLeft: Int, oldTop: Int, oldRight: Int, oldBottom: Int) { view.removeOnLayoutChangeListener(this) doOnWidthAndHeightKnown() } })

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@MOLSJEROEN ANDROID CAN SOMETIMES BE TEDIOUS view.addOnLayoutChangeListener( object : View.OnLayoutChangeListener { override fun onLayoutChange( view: View, left: Int, top: Int, right: Int, bottom: Int, oldLeft: Int, oldTop: Int, oldRight: Int, oldBottom: Int) { view.removeOnLayoutChangeListener(this) doOnWidthAndHeightKnown() } })

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@MOLSJEROEN ANDROID CAN SOMETIMES BE TEDIOUS view.addOnLayoutChangeListener( object : View.OnLayoutChangeListener { override fun onLayoutChange( view: View, left: Int, top: Int, right: Int, bottom: Int, oldLeft: Int, oldTop: Int, oldRight: Int, oldBottom: Int) { view.removeOnLayoutChangeListener(this) doOnWidthAndHeightKnown() } })

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@MOLSJEROEN ANDROID CAN SOMETIMES BE TEDIOUS view.addOnLayoutChangeListener( object : View.OnLayoutChangeListener { override fun onLayoutChange( view: View, left: Int, top: Int, right: Int, bottom: Int, oldLeft: Int, oldTop: Int, oldRight: Int, oldBottom: Int) { view.removeOnLayoutChangeListener(this) doOnWidthAndHeightKnown() } })

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@MOLSJEROEN KTX TO THE RESCUE view.doOnLayout { doOnWidthAndHeightKnown() }

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@MOLSJEROEN KTX UNDER THE HOOD inline fun View.doOnLayout( crossinline action: (view: View) -> Unit ) { if (ViewCompat.isLaidOut(this) && !isLayoutRequested) { action(this) } else { doOnNextLayout { action(it) } } }

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@MOLSJEROEN KTX UNDER THE HOOD inline fun View.doOnLayout( crossinline action: (view: View) -> Unit ) { if (ViewCompat.isLaidOut(this) && !isLayoutRequested) { action(this) } else { doOnNextLayout { action(it) } } }

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@MOLSJEROEN KTX UNDER THE HOOD inline fun View.doOnLayout( crossinline action: (view: View) -> Unit ) { if (ViewCompat.isLaidOut(this) && !isLayoutRequested) { action(this) } else { doOnNextLayout { action(it) } } }

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@MOLSJEROEN KTX UNDER THE HOOD inline fun View.doOnLayout( crossinline action: (view: View) -> Unit ) { if (ViewCompat.isLaidOut(this) && !isLayoutRequested) { action(this) } else { doOnNextLayout { action(it) } } }

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@MOLSJEROEN KTX UNDER THE HOOD inline fun View.doOnNextLayout( crossinline action: (view: View) -> Unit ) { addOnLayoutChangeListener(object : View.OnLayoutChangeListener { override fun onLayoutChange( view: View, left: Int, top: Int, right: Int, bottom: Int, oldLeft: Int, oldTop: Int, oldRight: Int, oldBottom: Int ) { view.removeOnLayoutChangeListener(this) action(view) } }) }

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@MOLSJEROEN WHAT IS KTX

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@MOLSJEROEN WHAT IS KTX

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@MOLSJEROEN WHAT IS KTX

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@MOLSJEROEN HOW TO USE KTX repositories { google() } dependencies { implementation "androidx.core:core:1.2.0" }

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@MOLSJEROEN HOW TO USE KTX repositories { google() } dependencies { implementation "androidx.core:core:1.2.0" }

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@MOLSJEROEN HOW TO USE KTX repositories { google() } dependencies { implementation “androidx.core:core-ktx:1.2.0” }

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CRASH COURSE

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@MOLSJEROEN ANIMATIONS animator.addListener(object : Animator.AnimatorListener { override fun onAnimationStart(animation: Animator?) = doSomething(animation!!) override fun onAnimationRepeat(animation: Animator?) = doSomething(animation!!) override fun onAnimationEnd(animation: Animator?) = doSomething(animation!!) override fun onAnimationCancel(animation: Animator?) = doSomething(animation!!) })

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@MOLSJEROEN ANIMATIONS val animator = ObjectAnimator.ofFloat(view, ALPHA, 0f, 1f) animator.doOnStart { doSomething(it) } animator.doOnRepeat { doSomething(it) } animator.doOnCancel { doSomething(it) } animator.doOnEnd { doSomething(it) }

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@MOLSJEROEN ANIMATIONS val animator = ObjectAnimator.ofFloat(view, View.ALPHA, 0f, 1f) animator.doOnPause { doSomething(it) } animator.doOnResume { doSomething(it) }

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@MOLSJEROEN SYSTEM SERVICES // requires android M val layoutInflater = context .getSystemService(LayoutInflater::class.java)

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@MOLSJEROEN SYSTEM SERVICES // requires android M val layoutInflater = context .getSystemService(LayoutInflater::class.java) // any Android version context.getSystemService()

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@MOLSJEROEN SHAREDPREFERENCES sharedPrefs.edit().putBoolean("key", true).apply()

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@MOLSJEROEN SHAREDPREFERENCES sharedPrefs.edit().putBoolean("key", true).apply() sharedPrefs.edit { putBoolean("key", true) } sharedPrefs.edit(commit = true) { putBoolean("key", true) }

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@MOLSJEROEN COLORS val red = Color.parseColor("#ff0000") val colorDrawable = ColorDrawable(red)

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@MOLSJEROEN COLORS val red = Color.parseColor("#ff0000") val colorDrawable = ColorDrawable(red) val red = "#ff0000".toColorInt() val colorDrawable = red.toDrawable()

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@MOLSJEROEN URI AND FILE val uri = “https://jeroenmols.com/blog”.toUri() val file = uri.toFile() val fileUri = file.toUri()

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@MOLSJEROEN VIEW view.doOnLayout { } view.doOnNextLayout { } view.doOnPreDraw { } view.doOnAttach { } view.doOnDetach { } view.marginStart view.marginEnd view.marginLeft view.marginRight view.marginTop view.marginBottom

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@MOLSJEROEN VIEW view.updateLayoutParams { width = 200 // strong typed access height = 200 } view.updatePadding(right = 10) // only assign one val bitmap = view.drawToBitmap()

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@MOLSJEROEN VIEW VISIBILITY if (view.visibility == View.VISIBLE) { // do something } view.visibility = View.VISIBLE

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@MOLSJEROEN VIEW VISIBILITY if (view.visibility == View.VISIBLE) { // do something } view.visibility = View.VISIBLE if (view.isVisible) { // do something } view.isVisible = false // View.GONE

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@MOLSJEROEN VIEWGROUP viewGroup.contains(view) viewGroup.forEach { } viewGroup.isEmpty() viewGroup.isNotEmpty() viewGroup += view viewGroup -= view

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@MOLSJEROEN TEXTVIEW editText.addTextChangedListener(object : TextWatcher { override fun afterTextChanged(s: Editable?) = doWork() override fun beforeTextChanged(s: CharSequence?, start: Int,…) = doWork() override fun onTextChanged(s: CharSequence?, start: Int,…) = doWork() })

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@MOLSJEROEN TEXTVIEW editText.addTextChangedListener(object : TextWatcher { override fun afterTextChanged(s: Editable?) = doWork() override fun beforeTextChanged(s: CharSequence?, start: Int,…) = doWork() override fun onTextChanged(s: CharSequence?, start: Int,…) = doWork() }) editText.doOnTextChanged { text, start, count, after -> doWork() } editText.doAfterTextChanged { doWork() } editText.doBeforeTextChanged { text, start, count, after -> doWork() }

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@MOLSJEROEN VIEWMODELS - ACTIVITY // scoped to activity val viewmodel = ViewModelProviders.of(this) .get(MyViewModel::class.java)

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@MOLSJEROEN VIEWMODELS - ACTIVITY // scoped to activity val viewmodel = ViewModelProviders.of(this) .get(MyViewModel::class.java) // scoped to activity val viewModel by viewModels()

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@MOLSJEROEN VIEWMODELS - FRAGMENT // scoped to fragment val viewModel = ViewModelProviders.of(this) .get(MyViewModel::class.java) // scoped to activity val viewModel = ViewModelProviders.of(requireActivity()) .get(MyViewModel::class.java)

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@MOLSJEROEN VIEWMODELS - FRAGMENT // scoped to fragment val viewModel = ViewModelProviders.of(this) .get(MyViewModel::class.java) // scoped to activity val viewModel = ViewModelProviders.of(requireActivity()) .get(MyViewModel::class.java) // scoped to fragment val viewModel by viewModels() // scoped to activity val activityViewModel by activityViewModels()

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@MOLSJEROEN VIEWMODELS - FACTORY val viewModel = ViewModelProviders.of(this, VModelFactory()) .get(MyViewModel::class.java)

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@MOLSJEROEN VIEWMODELS - FACTORY val viewModel = ViewModelProviders.of(this, VModelFactory()) .get(MyViewModel::class.java) val viewModel by viewModels() { VModelFactory() }

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@MOLSJEROEN FRAGMENT TRANSACTIONS fragmentManager.beginTransaction() .replace(R.id.container, Fragment()).commit()

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@MOLSJEROEN FRAGMENT TRANSACTIONS fragmentManager.beginTransaction() .replace(R.id.container, Fragment()).commit() fragmentManager.commit { replace(R.id.container, Fragment()) } fragmentManager.commit(allowStateLoss = true) { replace(R.id.container, Fragment()) }

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@MOLSJEROEN COROUTINE SCOPES AppCompatActivity().lifecycleScope.launch { } Fragment().lifecycleScope.launch { } ViewModel().viewModelScope.launch { }

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@MOLSJEROEN AND MANY MORE Benchmark Graphics Spannable SparseArrays Ranges Menu Lifecycle Livedata & flow Navigation Paging Preferences Room Slices Sqlite Workmanager Playcore … bit.ly/ktx-extensions

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WRITE YOUR OWN

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@MOLSJEROEN LIMIT DECIMALS IN EDITTEXT fun EditText.limitDecimalsTo(numDecimals: Int) { filters += InputFilter { s, start, end, d, dstart, dend -> val newText = s.subSequence(start, end).toString() val result = StringBuilder(d) .replace(dstart, dend, newText).toString() val regex = “[0-9]*((\\.[0-9]{0,$numDecimals})?)||(\\.)?" .toRegex() if (regex.matches(result)) null else "" } } editText.limitDecimalsTo(2)

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@MOLSJEROEN LIMIT DECIMALS IN EDITTEXT fun EditText.limitDecimalsTo(numDecimals: Int) { filters += InputFilter { s, start, end, d, dstart, dend -> val newText = s.subSequence(start, end).toString() val result = StringBuilder(d) .replace(dstart, dend, newText).toString() val regex = “[0-9]*((\\.[0-9]{0,$numDecimals})?)||(\\.)?" .toRegex() if (regex.matches(result)) null else "" } } editText.limitDecimalsTo(2)

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@MOLSJEROEN LIMIT DECIMALS IN EDITTEXT fun EditText.limitDecimalsTo(numDecimals: Int) { filters += InputFilter { s, start, end, d, dstart, dend -> val newText = s.subSequence(start, end).toString() val result = StringBuilder(d) .replace(dstart, dend, newText).toString() val regex = “[0-9]*((\\.[0-9]{0,$numDecimals})?)||(\\.)?" .toRegex() if (regex.matches(result)) null else "" } } editText.limitDecimalsTo(2)

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@MOLSJEROEN TOAST fun Fragment.toast(@StringRes message: Int) = Toast.makeText(context, message, LENGTH_SHORT).show() fun Fragment.toast(message: String) = Toast.makeText(context, message, LENGTH_SHORT).show() toast(R.id.mymessage) toast("Hello there")

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@MOLSJEROEN TOAST fun Fragment.toast(@StringRes message: Int) = Toast.makeText(context, message, LENGTH_SHORT).show() fun Fragment.toast(message: String) = Toast.makeText(context, message, LENGTH_SHORT).show() toast(R.id.mymessage) toast("Hello there")

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@MOLSJEROEN FLOAT fun Float.isDecimalNumber() = this % 1 > 0.0001 fun Float.decimalsOrRound(digits: Int) = if (isDecimalNumber()) { String.format("%.${digits}f", this) } else { String.format("%.0f", this) } 12.3f.isDecimalNumber() 12.3001f.decimalsOrRound(2)

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@MOLSJEROEN FLOAT fun Float.isDecimalNumber() = this % 1 > 0.0001 fun Float.decimalsOrRound(digits: Int) = if (isDecimalNumber()) { String.format("%.${digits}f", this) } else { String.format("%.0f", this) } 12.3f.isDecimalNumber() 12.3001f.decimalsOrRound(2)

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@MOLSJEROEN TABSELECTED LISTENER fun TabLayout.doOnTabSelected(listener: (text: String) -> Unit) { clearOnTabSelectedListeners() addOnTabSelectedListener(object : TabLayout.OnTabSelectedListener { override fun onTabReselected(tab: TabLayout.Tab?) = Unit override fun onTabUnselected(tab: TabLayout.Tab?) = Unit override fun onTabSelected(tab: TabLayout.Tab?) = listener.invoke(tab!!.text.toString()) }) } tabLayout.doOnTabSelected { doSomething() }

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@MOLSJEROEN TABSELECTED LISTENER fun TabLayout.doOnTabSelected(listener: (text: String) -> Unit) { clearOnTabSelectedListeners() addOnTabSelectedListener(object : TabLayout.OnTabSelectedListener { override fun onTabReselected(tab: TabLayout.Tab?) = Unit override fun onTabUnselected(tab: TabLayout.Tab?) = Unit override fun onTabSelected(tab: TabLayout.Tab?) = listener.invoke(tab!!.text.toString()) }) } tabLayout.doOnTabSelected { doSomething() }

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DISCOVER MORE

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@MOLSJEROEN LEARN MORE ABOUT KTX bit.ly/ktx-docs bit.ly/ktx-extensions bit.ly/ktx-source

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WRAP UP

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@MOLSJEROEN IDIOMATIC CODE SIMPLIFY DEVELOPMENT REDUCE ERRORS WRITE YOUR OWN GET INSPIRED

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@MOLSJEROEN HTTPS://JEROENMOLS.COM/BLOG

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@MOLSJEROEN IMAGE CREDITS Welcome image by Clement127 https://flic.kr/p/QdpUY8 Official Android and Google logo's Font awesome https://fontawesome.com/

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MOLSJEROEN