In Part 1 we dealt with the simplest form of initialization with the primary constructor: class Planet( val diameter: Int, val distanceToSun: Double, val mass: Double ) But wait: there is more: Init block The primary constructor cannot contain any code so init block for the rescue: class Planet( val diameter: Int, val distanceToSun: Double,…
Dependency Add the following to your dependencies implementation(org.jetbrains.kotlinx:kotlinx-datetime:0.2.0) Usage import kotlinx.datetime.* val today = Clock.System.todayAt(TimeZone.currentSystemDefault()) If you target Android devices running below API 26, you need to use Android Gradle plugin 4.0 or newer and enable core library desugaring. https://github.com/Kotlin/kotlinx-datetime
In Passing data between fragments using SafeArgs I showed You how to pass data between -well- fragments. This included all basic / built-in types like Strings and Integers. In this part I will show you how you can pass custom objects.
In Log4j2 for Kotlin I’ve showed you how to configure a basic logger with log4j2. If you use a PatternLayout like this
Motivation Logging is a common good practice in software engineering. It enables you to monitor applications in production to gather information about crashes and other malfunctions for further analysis. It is the “little brother” of debugging and often a precursor for setting up test cases which can lead to reproducing the bugs on the developers…
If you are using Gradle and you want to run a Kotlin script you have to add the following to your build.gradle file dependencies { implementation “org.jetbrains.kotlin:kotlin-stdlib” implementation ‘org.jetbrains.kotlin:kotlin-script-runtime:1.4.32’ }
Sending data private void openVideoActivity(String video) { Intent newActivity = new Intent(this, PlayerActivity.class); newActivity.putExtra(“videoId”, video); startActivity(newActivity); } Retrieving data final String videoID = getIntent().getExtras().getString(“videoID”); In Kotlin it looks like this: val intent = Intent(this, NewActivity::class.java).apply { putExtra(“EXTRA_MESSAGE”, “Test 123”) } startActivity(intent) Retrieving val message = intent.getStringExtra(“EXTRA_MESSAGE”) Further Reading Passing data between fragments using SafeArgs…
Code class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) Log.d(“LifecycleTest”, “onCreate”) } override fun onStart() { super.onStart() Log.d(“LifecycleTest”, “onStart”) } override fun onResume() { super.onResume() Log.d(“LifecycleTest”, “onResume”) } override fun onPause() { super.onPause() Log.d(“LifecycleTest”, “onPause”) } override fun onSaveInstanceState(outState: Bundle) { super.onSaveInstanceState(outState) Log.d(“LifecycleTest”, “onSaveInstanceState”) } override fun onRestoreInstanceState(savedInstanceState: Bundle) { Log.d(“LifecycleTest”,…
Conditionals This is a pretty quick one: Kotlin has the standard Java if / else if / else statements val age = 12 if (age < 5) { println(“Go to kindergarten”) } else if (age == 5) { println(“Go to pre-school”) } else if (age > 5 && age <= 17) { println(“Go to grade…
Motivation I wanted to try writing an Android app. In spite of using plain old Java I wanted to give the new kid on the block Kotlin (from the Jetbrains folks) a try. First observations Coming from a Python background it’s good to see that Kotlin doesn’t use semi-colons! But the curly braces from Java…