Android imageView Zoom-in and Zoom-Out using Kotlin?

This example demonstrates how to implement Android imageView zoom-in and Zoom out using kotlin.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
   android:layout_width="match_parent"
   android:layout_height="match_parent"
   android:gravity="center"
   android:orientation="vertical"
   android:padding="16dp"
   tools:context=".MainActivity">
   <ImageView
      android:id="@+id/imageView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:src="@drawable/image" />
</LinearLayout>

Step 3 − Add the following code to src/MainActivity.kt

import android.os.Bundle
import android.view.MotionEvent
import android.view.ScaleGestureDetector
import android.view.ScaleGestureDetector.SimpleOnScaleGestureListener
import android.widget.ImageView
import androidx.appcompat.app.AppCompatActivity
import kotlin.math.max
import kotlin.math.min
class MainActivity : AppCompatActivity() {
   private lateinit var scaleGestureDetector: ScaleGestureDetector
   private var scaleFactor = 1.0f
   private lateinit var imageView: ImageView
   override fun onCreate(savedInstanceState: Bundle?) {
      super.onCreate(savedInstanceState)
      setContentView(R.layout.activity_main)
      title = "KotlinApp"
      imageView = findViewById(R.id.imageView)
      scaleGestureDetector = ScaleGestureDetector(this, ScaleListener())
   }
   override fun onTouchEvent(motionEvent: MotionEvent): Boolean {
      scaleGestureDetector.onTouchEvent(motionEvent)
      return true
   }
   private inner class ScaleListener : SimpleOnScaleGestureListener() {
      override fun onScale(scaleGestureDetector: ScaleGestureDetector): Boolean {
         scaleFactor *= scaleGestureDetector.scaleFactor
         scaleFactor = max(0.1f, min(scaleFactor, 10.0f))
         imageView.scaleX = scaleFactor
         imageView.scaleY = scaleFactor
         return true
      }
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.q11">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click the Run icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen