How to Zoom-in and zoom-out ImageView in Kotlin

In this android kotlin source code example, we are going to Zoom-in and zoom-out ImageView in Android Kotlin.

You can copy and adopt this source code example to your Kotlin android project without reinventing the wheel.

Below is a step by step source code to Zoom-in and zoom-out ImageView in Android Kotlin.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".imageView.ImageViewActivity10">

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/profilepic"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.kt

import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import android.widget.ImageView
import com.bluapp.kotlinview.R
import android.view.ScaleGestureDetector
import android.view.MotionEvent


class ImageViewActivity10 : AppCompatActivity() {
    private var mScaleGestureDetector: ScaleGestureDetector? = null
    private var mScaleFactor = 1.0f
    private var imageView: ImageView? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_image_view10)
        imageView = findViewById<ImageView>(R.id.imageView)
        mScaleGestureDetector = ScaleGestureDetector(this, ScaleListener())
    }

    override fun onTouchEvent(motionEvent: MotionEvent): Boolean {
        mScaleGestureDetector?.onTouchEvent(motionEvent)
        return true
    }

    private inner class ScaleListener : ScaleGestureDetector.SimpleOnScaleGestureListener() {
        override fun onScale(scaleGestureDetector: ScaleGestureDetector): Boolean {
            mScaleFactor *= scaleGestureDetector.scaleFactor
            mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f))
            imageView?.setScaleX(mScaleFactor)
            imageView?.setScaleY(mScaleFactor)
            return true
        }
    }
}

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