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Kotlin for Android - Documentation and Code Snippets

All you need to start creating Android app in Kotlin. Kotlin Syntax Print to console print("Amit Shekhar") println("Amit Shekhar") Constants and Variables var name = "Amit Shekhar" val name = "Amit Shekhar" Assigning the null value var otherName : String? otherName = null Verify if value is null text?.let { val length = text.length } // or simply val length = text?.length Concatenation of strings var firstName = "Amit" var lastName = "Shekhar" var message = "My name is: $firstName$lastName" New line in string val text = """ |First Line |Second Line |Third Line """.

How to get currently running applications in android ?

Use this code in your app’s `src/MainActivity.kt' file. import import import android.content.Context import android.os.Bundle import android.widget.TextView import import java.util.* class MainActivity : AppCompatActivity() { override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) setContentView(R.layout.activity_main) title = "KotlinApp" val textView: TextView = findViewById( val activityManager = getSystemService(Context.ACTIVITY_SERVICE) as ActivityManager val recentTasks: List<RunningTaskInfo> = Objects.requireNonNull(activityManager).getRunningTasks(Int.MAX_VALUE) for (i in recentTasks.indices) { textView.text = "Application executed: ${recentTasks[i].baseActivity!!.toShortString()}ID: ${recentTasks[i].id}" } } } Make sure you have a TextView with id textView in your XML layout.

How do you animate the change of background color of a view on Android ?

The idea is to use this code snippet. ColorDrawable[] colorDrawables = { new ColorDrawable(Color.RED), new ColorDrawable(Color.BLUE), new ColorDrawable(Color.GREEN) }; TransitionDrawable transitionDrawable = new TransitionDrawable(colorDrawables); textView.setBackground(transitionDrawable); transitionDrawable.startTransition(2000); In this code snippet, we created a list of colorDrawables, then feed them to the TransitionDrawable. And now we have an animating color change, so we pass it to the setBackground to get the animating colors in the background. Got the idea ? let’s create a complete code example.

How to change background color of selected item in listview in android ?

The main idea is to use view.setBackgroundColor(getColor(R.color.colorAccent)) to the selected view (list item). Let’s see a complete example. use this xml code in res/layout/activity_main.xml. <?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="" xmlns:tools="" android:layout_width="match_parent" android:layout_height="match_parent" android:padding="8dp" tools:context=".MainActivity"> <ListView android:id="@+id/listView" android:layout_width="match_parent" android:layout_height="match_parent" /> </RelativeLayout> use this Kotlin code in src/MainActivity.kt. import android.os.Build import import android.os.Bundle import android.widget.ArrayAdapter import android.widget.ListView class MainActivity : AppCompatActivity() { var operatingSystem: Array<String> = arrayOf("Android", "IPhone", "WindowsMobile", "Blackberry", "WebOS", "Ubuntu", "Windows7", "Max OS X") override fun onCreate(savedInstanceState: Bundle?

How to Change Listview Item Color in Android

The idea is to create an a list item xml, and give it the design choices you want. If you want to change the list item color, use this xml code android:textColor="@android:color/holo_orange_dark". If you want to change the text to italic or bold, use this xml android:textStyle="italic|bold". And even if you want to change the font itself, you can by this font-family property in xml android:fontFamily="sans-serif-condensed". Now, you got the idea.