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+Christina Lee @RunChristinaRun +Jake Wharton @JakeWharton Kotlin is here Life is great and everything will be OK

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MainActivity.java public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); }1 }2

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MainActivity.java public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); }1 }2

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MainActivity.java public class MainActivity extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); }1 }2

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MainActivity.java public class MainActivity extends Activity { @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); }1 }2 @Nullable

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MainActivity.java public class MainActivity extends Activity { @Override protected void onCreate(@Nullable Bundle savedInstanceState) { super.onCreate(savedInstanceState); }1 }2

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MainActivity.kt class MainActivity : Activity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) }1 }2

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MainActivity.kt class MainActivity : Activity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) }1 }2

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MainActivity.kt class MainActivity : Activity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) }1 }2

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TextView.java public float getAlpha() { // Retrieve value... }

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TextView.java public float getAlpha() { // Retrieve value... } public void setAlpha(float alpha) { // Set value... }

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TextView.java public float getAlpha() { // Retrieve value... } public void setAlpha(float alpha) { // Set value... } TextView tv = // ... Log.d("MainActivity", "Alpha: " + tv.getAlpha()); tv.setAlpha(0f); MainActivity.java

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TextView.java public float getAlpha() { // Retrieve value... } public void setAlpha(float alpha) { // Set value... } MainActivity.kt val tv = // ... Log.d("MainActivity", "Alpha: " + tv.alpha) tv.alpha = 0f

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TextView.java public float getAlpha() { // Retrieve value... }1 public void setAlpha(float alpha) { // Set value... }2 MainActivity.kt val tv = // ... Log.d("MainActivity", "Alpha: " + tv.alpha) tv.alpha = 0f

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TextView.java public float getAlpha() { // Retrieve value... }1 public void setAlpha(float alpha) { // Set value... }2 MainActivity.kt val tv = // ... Log.d("MainActivity", "Alpha: " + tv.alpha) tv.alpha = 0f

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TextView.java public float getAlpha() { // Retrieve value... }1 public void setAlpha(float alpha) { // Set value... }2 MainActivity.kt val tv = // ... Log.d("MainActivity", "Alpha: " + tv.alpha) tv.alpha = 0f

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MainActivity.java LinearLayout views = // ... for (int i = 0; i < views.getChildCount(); i++) { View view = views.getChildAt(i); // TODO do something with view }

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MainActivity.kt val views = // ... for (index in 0 until views.childCount) { val view = views.getChildAt(index) // TODO do something with view }

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MainActivity.kt val views = // ... for (index in 0 until views.childCount) { val view = views.getChildAt(index) // TODO do something with view }1

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MainActivity.kt val views = // ... for (index in 0 until views.childCount) { val view = views.getChildAt(index) // TODO do something with view }1

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MainActivity.kt val views = // ... for (index in 0 until views.childCount) { val view = views.getChildAt(index) // TODO do something with view }

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MainActivity.kt val views = // ... for (index in 0 until views.childCount) {Z val view = views.getChildAt(index) // TODO do something with view }1 ViewGroups.kt fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3 . Each ->

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MainActivity.kt val views = // ... views.forEach {Zview -> // TODO do something with view }1 ViewGroups.kt fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3 val = views.getChildAt(i)

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MainActivity.kt val views = // ... views.forEach {Zview -> // TODO do something with view }1 ViewGroups.kt fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3

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MainActivity.kt val views = // ... views.forEach {Zview -> // TODO do something with view }1 ViewGroups.kt fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3

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MainActivity.kt val views = // ... views.forEach {Zview -> // TODO do something with view }1 ViewGroups.kt fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3

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MainActivity.kt val views = // ... views.forEach {Zview -> // TODO do something with view }1 ViewGroups.kt fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3

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MainActivity.kt val views = // ... views.forEach {Zview -> // TODO do something with view }1 ViewGroups.kt inline fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3 inline

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MainActivity.kt val views = // ... views.forEach {Zview -> // TODO do something with view }1 ViewGroups.kt inline fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3

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MainActivity.kt val views = // ... views.forEach {Zview -> /* ... */ }1 views.forEachIndexed { index, view -> /* ... */ }1 ViewGroups.kt inline fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3 inline fun ViewGroup.forEachIndexed(action: (Int, View) -> Unit) { for (index in 0 until childCount) { action(index, getChildAt(index)) } } / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... views.forEach {Zview -> /* ... */ }1 views.forEachIndexed { index, view -> /* ... */ }1 ViewGroups.kt inline fun ViewGroup.forEach(action: (View) -> Unit) { for (index in 0 until childCount) { action(getChildAt(index)) }2 }3 inline fun ViewGroup.forEachIndexed(action: (Int, View) -> Unit) { for (index in 0 until childCount) { action(index, getChildAt(index)) } } / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... / / T O D O d o s o m e t h i n g w i t h v i e w ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index)

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MainActivity.kt val views = // ... val first = views[0] ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views.get(0) views.minusAssign(first) views.plusAssign(first) if (views.contains(first)) doSomething() ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 / / T O D O d o s o m e t h i n g w i t h v i e w in

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() Log.d("MainActivity", "View count: ${views.size}") ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 val ViewGroup.size: Int get() = childCount / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() Log.d("MainActivity", "View count: ${views.size}") ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 val ViewGroup.size: Int get() = childCount / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() Log.d("MainActivity", "View count: ${views.size}") ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 val ViewGroup.size: Int get() = childCount / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() Log.d("MainActivity", "View count: ${views.size}") ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 val ViewGroup.size: Int get() = childCount / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... val first = views[0] views -= first views += first if (first in views) doSomething() Log.d("MainActivity", "View count: ${views.size}") ViewGroups.kt operator fun ViewGroup.get(index: Int): View? = getChildAt(index) operator fun ViewGroup.minusAssign(child: View) = removeView(child) operator fun ViewGroup.plusAssign(child: View) = addView(child) operator fun ViewGroup.contains(child: View) = indexOfChild(child) != -1 val ViewGroup.size: Int get() = childCount / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... / / T O D O d o s o m e t h i n g w i t h v i e w ViewGroups.kt fun ViewGroup.children() = object : Iterable { override fun iterator() = object : Iterator { var index = 0 override fun hasNext() = index < childCount override fun next() = getChildAt(index++) } }

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MainActivity.kt val views = // ... for (view in views.children()) { // TODO do something with view }1 ViewGroups.kt fun ViewGroup.children() = object : Iterable { override fun iterator() = object : Iterator { var index = 0 override fun hasNext() = index < childCount override fun next() = getChildAt(index++) }2 }3 / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... for (view in views.children()) { // TODO do something with view }1 val visibleHeight = views.children() .filter { it.visibility == View.VISIBLE } .sumBy { it.measuredHeight } ViewGroups.kt fun ViewGroup.children() = object : Iterable { override fun iterator() = object : Iterator { var index = 0 override fun hasNext() = index < childCount override fun next() = getChildAt(index++) }2 }3 / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.kt val views = // ... for (view in views.children()) { // TODO do something with view } val visibleHeight = views.children() .filter { it.visibility == View.VISIBLE } .sumBy { it.measuredHeight } ViewGroups.kt fun ViewGroup.children() = object : Iterable { override fun iterator() = object : Iterator { var index = 0 override fun hasNext() = index < childCount override fun next() = getChildAt(index++) } } / / T O D O d o s o m e t h i n g w i t h v i e w

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MainActivity.java Trace.beginSection(sectionName); expensiveCalculation(); Trace.endSection();

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MainActivity.java Trace.beginSection(sectionName); expensiveCalculation(); Trace.endSection(); Traces.kt inline fun trace(sectionName: String, body: () -> Unit) { Trace.beginSection(sectionName) try { body() }2finally { Trace.endSection() }3 }4

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Traces.kt inline fun trace(sectionName: String, body: () -> Unit) {Z Trace.beginSection(sectionName) try { body() }2finally { Trace.endSection() }3 }4 MainActivity.kt trace("foo") { expensiveCalculation() }1

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Traces.kt inline fun trace(sectionName: String, body: () -> T): T {Z Trace.beginSection(sectionName) try { return body() }2finally { Trace.endSection() }3 }4 Unit MainActivity.kt trace("foo") { expensiveCalculation() }1 T T return

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Traces.kt inline fun trace(sectionName: String, body: () -> T): T {Z Trace.beginSection(sectionName) try { return body() }2finally { Trace.endSection() }3 }4 MainActivity.kt val result = trace("foo") { expensiveCalculation() }1 val result = T T return

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Traces.kt inline fun trace(sectionName: String, body: () -> T): T {Z Trace.beginSection(sectionName) try { return body() }2finally { Trace.endSection() }3 }4 MainActivity.kt val result = trace("foo") { expensiveCalculation() }1

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MainActivity.java SQLiteDatabase db = // ... db.beginTransaction(); try { db.delete("users", "first_name = ?", new String[] { "jake" }); } finally { db.endTransaction(); }1

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MainActivity.java SQLiteDatabase db = // ... db.beginTransaction(); try { db.delete("users", "first_name = ?", new String[] { "jake" }); db.setTransactionSuccessful(); } finally { db.endTransaction(); }1

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SQLiteDatabase db = // ... db.beginTransaction(); try { db.delete("users", "first_name = ?", new String[] { "jake" }); db.setTransactionSuccessful(); } finally { db.endTransaction(); }1 Databases.kt inline fun SQLiteDatabase.transaction(body: () -> Unit) { beginTransaction() try { body() setTransactionSuccessful() } finally { endTransaction() }2 }1

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MainActivity.kt val db = // ... db.transaction {4 db.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: () -> Unit) { beginTransaction() try { body()X setTransactionSuccessful() } finally { endTransaction() }2 }1 1 SQLiteDatabase db.beginTransaction(); try new String[] { } db.setTransactionSuccessful(); finally { db.endTransaction(); }1

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MainActivity.kt val db = // ... db.transaction {4 db.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: () -> Unit) { beginTransaction() try { body()X setTransactionSuccessful() } finally { endTransaction() }2 }1 1

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MainActivity.kt val db = // ... db.transaction {4 db.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: () -> Unit) { beginTransaction() try { body()X setTransactionSuccessful() } finally { endTransaction() }2 }1 1

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MainActivity.kt val db = // ... db.transaction {4 db.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: (SQLiteDatabase) -> Unit) { beginTransaction() try { body()X setTransactionSuccessful() } finally { endTransaction() }2 }1 1 SQLiteDatabase

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MainActivity.kt val db = // ... db.transaction {4 db.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: (SQLiteDatabase) -> Unit) { beginTransaction() try { body(this)X setTransactionSuccessful() } finally { endTransaction() }2 }1 1 SQLiteDatabase body(this)X

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MainActivity.kt val db = // ... db.transaction {4 it.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: (SQLiteDatabase) -> Unit) { beginTransaction() try { body(this) setTransactionSuccessful() } finally { endTransaction() }2 }1 1 it.delete SQLiteDatabase body(this)X

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MainActivity.kt val db = // ... db.transaction {4 it.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: (SQLiteDatabase) -> Unit) { beginTransaction() try { body(this)F setTransactionSuccessful() } finally { endTransaction() }2 }1 1

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MainActivity.kt val db = // ... db.transaction {4 it.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: (SQLiteDatabase) -> Unit) { beginTransaction() try { body(this)F setTransactionSuccessful() } finally { endTransaction() }2 }1 1

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MainActivity.kt val db = // ... db.transaction {4 it.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: (SQLiteDatabase) -> Unit) { beginTransaction() try { body(this)F setTransactionSuccessful() } finally { endTransaction() }2 }1 1

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MainActivity.kt val db = // ... db.transaction {4 it.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: SQLiteDatabase.() -> Unit) { beginTransaction() try { body(this)F setTransactionSuccessful() } finally { endTransaction() }2 }1 1 SQLiteDatabase.() -> Unit

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MainActivity.kt val db = // ... db.transaction {4 it.delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: SQLiteDatabase.() -> Unit) { beginTransaction() try { body() setTransactionSuccessful() } finally { endTransaction() }2 }1 1 SQLiteDatabase.() -> Unit body()F

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it. MainActivity.kt val db = // ... db.transaction {4 delete("users", "first_name = ?", arrayOf("jake")) }3 Databases.kt inline fun SQLiteDatabase.transaction(body: SQLiteDatabase.() -> Unit) { beginTransaction() try { body() setTransactionSuccessful() } finally { endTransaction() }2 }1 1 delete SQLiteDatabase.() -> Unit body()F

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MainActivity.kt val db = // ... db.transaction {4 delete("users", "first_name = ?", arrayOf("jake"))G }3 Databases.kt inline fun SQLiteDatabase.transaction(body: SQLiteDatabase.() -> Unit) { beginTransaction() try { body() setTransactionSuccessful() } finally { endTransaction() }2 }1 1

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MainActivity.kt = // ... "jake" Databases.kt inline fun SQLiteDatabase.transaction(body: SQLiteDatabase.() -> Unit) { beginTransaction() try { body() setTransactionSuccessful() } finally { endTransaction() }2 }1 1 class UserPersistence(private val db: SQLiteDatabase) { fun deleteByFirstName(name: String) { db.transaction { delete("users", "first_name = ?", arrayOf(name))G }3 } } UserPersistence.kt

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MainActivity.kt = // ... "jake" Databases.kt inline fun SQLiteDatabase.transaction(body: SQLiteDatabase.() -> Unit) { beginTransaction() try { body() setTransactionSuccessful() } finally { endTransaction() }2 }1 1 class UserPersistence(private val db: SQLiteDatabase) { fun deleteByFirstName(name: String) { db.transaction { delete("users", "first_name = ?", arrayOf(name))G }3 } } UserPersistence.kt

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class UserPersistence(private val db: SQLiteDatabase) { fun deleteByFirstName(name: String) { db.transaction { delete("users", "first_name = ?", arrayOf(name))G }3 }2 }1 UserPersistence.kt

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class UserPersistence(private val db: SQLiteDatabase) { private val deleteByFirstName = db.compileStatement( "DELETE FROM users WHERE first_name = ?") fun deleteByFirstName(name: String) { db.transaction { deleteByFirstName.bindString(1, name) deleteByFirstName.execute() }3 }2 }1 UserPersistence.kt delete(" ", " , arrayOf( ))G

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sssssssssssss class UserPersistence(private val db: SQLiteDatabase) { private val deleteByFirstName = db.compileStatement( "DELETE FROM users WHERE first_name = ?") fun deleteByFirstName(name: String) { db.transaction { deleteByFirstName.bindString(1, name) deleteByFirstName.execute() }3 }2 }1 UserPersistence.kt

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sssssssssssss class UserPersistence(private val db: SQLiteDatabase) { private val deleteByFirstName by lazy { db.compileStatement("DELETE FROM users WHERE first_name = ?") } fun deleteByFirstName(name: String) { db.transaction { deleteByFirstName.bindString(1, name) deleteByFirstName.execute() }3 }2 }1 UserPersistence.kt

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sssssssssssss class UserPersistence(private val db: SQLiteDatabase) { private val deleteByFirstName by lazy { db.compileStatement("DELETE FROM users WHERE first_name = ?") }X fun deleteByFirstName(name: String) { db.transaction { deleteByFirstName.bindString(1, name) deleteByFirstName.execute() }3 }2 }1 UserPersistence.kt

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private val deleteByFirstName by lazy { db.compileStatement("DELETE FROM users WHERE first_name = ?") }X

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private val deleteByFirstName by lazy { db.compileStatement("DELETE FROM users WHERE first_name = ?") }X private val name by Delegates.observable("jane") { old, new, prop -> println("Name changed from $old to $new") }

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private val deleteByFirstName by lazy { db.compileStatement("DELETE FROM users WHERE first_name = ?") }X private val name by Delegates.observable("jane") { old, new, prop -> println("Name changed from $old to $new") } private val address by Delegates.notNull()

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private val deleteByFirstName by lazy { db.compileStatement("DELETE FROM users WHERE first_name = ?") }X private val name by Delegates.observable("jane") { old, new, prop -> println("Name changed from $old to $new") } private val address by Delegates.notNull() private val nameView by bindView(R.id.name)

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private val deleteByFirstName by lazy { db.compileStatement("DELETE FROM users WHERE first_name = ?") }X private val name by Delegates.observable("jane") { old, new, prop -> println("Name changed from $old to $new") } private val address by Delegates.notNull() private val nameView by bindView(R.id.name)

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class MyListener : TransitionListener { override fun onTransitionEnd(transition: Transition) { } override fun onTransitionResume(transition: Transition) { } override fun onTransitionPause(transition: Transition) { } override fun onTransitionCancel(transition: Transition) { } override fun onTransitionStart(transition: Transition) { }Y }X

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class MyListener : TransitionListener { override fun onTransitionStart(transition: Transition) { }Y }X

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class MyListener : TransitionListener { override fun onTransitionStart(transition: Transition) { }Y }X object EmptyTransitionListener : TransitionListener { override fun onTransitionEnd(transition: Transition) {} override fun onTransitionResume(transition: Transition) {} override fun onTransitionPause(transition: Transition) {} override fun onTransitionCancel(transition: Transition) {} override fun onTransitionStart(transition: Transition) {} }

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class MyListener : TransitionListener { override fun onTransitionStart(transition: Transition) { }Y }X object EmptyTransitionListener : TransitionListener { override fun onTransitionEnd(transition: Transition) {} override fun onTransitionResume(transition: Transition) {} override fun onTransitionPause(transition: Transition) {} override fun onTransitionCancel(transition: Transition) {} override fun onTransitionStart(transition: Transition) {} }

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class MyListener : TransitionListener {T override fun onTransitionStart(transition: Transition) { }Y }X object EmptyTransitionListener : TransitionListener { override fun onTransitionEnd(transition: Transition) {} override fun onTransitionResume(transition: Transition) {} override fun onTransitionPause(transition: Transition) {} override fun onTransitionCancel(transition: Transition) {} override fun onTransitionStart(transition: Transition) {} }G

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class MyListener : TransitionListener by EmptyTransitionListener {T override fun onTransitionStart(transition: Transition) { }Y }X object EmptyTransitionListener : TransitionListener { override fun onTransitionEnd(transition: Transition) {} override fun onTransitionResume(transition: Transition) {} override fun onTransitionPause(transition: Transition) {} override fun onTransitionCancel(transition: Transition) {} override fun onTransitionStart(transition: Transition) {} }G

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class MyListener : TransitionListener by EmptyTransitionListener {T override fun onTransitionStart(transition: Transition) { }Y }X object EmptyTransitionListener : TransitionListener { override fun onTransitionEnd(transition: Transition) {} override fun onTransitionResume(transition: Transition) {} override fun onTransitionPause(transition: Transition) {} override fun onTransitionCancel(transition: Transition) {} override fun onTransitionStart(transition: Transition) {} }G

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class PaymentRobot { fun amount(value: Long) { // TODO Espresso interactions } fun recipient(value: String) { // TODO Espresso interactions } fun send() { // TODO Espresso interactions } } PaymentRobot.kt

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@Test fun sendMoney() { PaymentRobot().apply { amount(4_00) recipient("foo@example.com") send() } } PaymentTest.kt

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class PaymentRobot { fun amount(value: Long) { // TODO Espresso interactions } fun recipient(value: String) { // TODO Espresso interactions } fun send() { // TODO Espresso interactions } } PaymentRobot.kt

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class PaymentRobot { fun amount(value: Long) { // TODO Espresso interactions } fun recipient(value: String) { // TODO Espresso interactions } fun send() { // TODO Espresso interactions } } PaymentRobot.kt fun payment(body: PaymentRobot.() -> Unit) = PaymentRobot().apply(body)

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class PaymentRobot { fun amount(value: Long) { // TODO Espresso interactions } fun recipient(value: String) { // TODO Espresso interactions } fun send() { // TODO Espresso interactions } } PaymentRobot.kt fun payment(body: PaymentRobot.() -> Unit) = PaymentRobot().apply(body)

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@Test fun sendMoney() { PaymentRobot().apply {T amount(4_00) recipient("foo@example.com") send() }T }G PaymentTest.kt p

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@Test fun sendMoney() { payment {T amount(4_00) recipient("foo@example.com") send() }T }G PaymentTest.kt

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sealed class Payloads { }G

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sealed class Payloads { data class Favorite(val favorited: Boolean) : Payloads() }G

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sealed class Payloads { data class Favorite(val favorited: Boolean) : Payloads() data class Retweet(val retweeted: Boolean) : Payloads() }G

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sealed class Payloads { data class Favorite(val favorited: Boolean) : Payloads() data class Retweet(val retweeted: Boolean) : Payloads() data class CountUpdate( val favorites: Long, val retweets: Long, val replies: Long) : Payloads() }G

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { }1

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { payloads.forEach { }2 }1

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { payloads.forEach { when (it) { }3 }2 }1

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { payloads.forEach { when (it) { is Favorite -> holder.favoriteIcon.isActivated = it.favorited }3 }2 }1

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { payloads.forEach { when (it) { is Favorite -> holder.favoriteIcon.isActivated = it.favorited }3 }2 }1

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { payloads.forEach { when (it) { is Favorite -> holder.favoriteIcon.isActivated = it.favorited }3 }2 }1 sealed class Payloads { data class Favorite(val favorited: Boolean) : Payloads() data class Retweet(val retweeted: Boolean) : Payloads() data class CountUpdate( val favorites: Long, val retweets: Long, val replies: Long) : Payloads() }G

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { payloads.forEach { when (it) { is Favorite -> holder.favoriteIcon.isActivated = it.favorited }3 }2 }1

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { payloads.forEach { when (it) { is Favorite -> holder.favoriteIcon.isActivated = it.favorited is Retweet -> holder.retweetIcon.isActivated = it.retweeted }3 }2 }1

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override fun onBindViewHolder(holder: TweetViewHolder, position: Int, payloads: List) { payloads.forEach { when (it) { is Favorite -> holder.favoriteIcon.isActivated = it.favorited is Retweet -> holder.retweetIcon.isActivated = it.retweeted is CountUpdate -> { holder.apply { favoriteCount.text = it.favorites.toString() retweetCount.text = it.retweets.toString() replyCount.text = it.replies.toString() }5 }4 }3 }2 }1

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It takes great salesmanship to convince a customer to buy something from you that isn't built or isn't finished. Fred Wilson

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Step 3 Step 2 Step 1

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Step 1 Step 3 You Step 2

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Step 3 Management Step 2 Step 1

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Team Step 3 Step 2 Step 1

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You Get excited.

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Never doubt that a small group of thoughtful, committed citizens can change the world; indeed,
 it's the only thing 
 that ever has. Margaret Mead (Def. not talking about tech)

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Be enthusiastic

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Adoption is work. If you want it, you need to earn it.

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Management Be persuasive.

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I call it my billion- dollar mistake. Sir Charles Antony Richard Hoare

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One of the most feared expressions in modern times is 'The computer is down.' Norman Ralph Augustine

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Jake Wharton @JakeWharton Type systems are a form of tests. I declare an expected type and the tests (aka compiler) validates the actual ones. 6:43 PM - 11 Jan 2017 74 Follow 16

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Team Do the work.

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Ellen Shapiro @designatednerd My style: “I’m the idiot who went down the rabbit hole first, and I’m here to tell you which path leads to fluffy bunnies vs. angry moles.” 14 Mar Ellen Shapiro @designatednerd My favorite bit of any talk I give is talking about the dumb shit I did so the audience doesn’t do it. Makes the hair pulled out worth it. 4:56 PM - 14 Mar 2017 1 Follow

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Define success

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http://blog.danlew.net/

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On-boarding should be a first class citizen

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Show up

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What’s next? Kotlin documentation and koans https://kotlinlang.org/ Android Kotlin documentation https://developer.android.com/kotlin/index.html Kotlin In Action Dimitry Jemerov, Svetlana Isakova

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+Christina Lee @RunChristinaRun #KotlinIsHere Thank you! +Jake Wharton @JakeWharton

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