Android Studio (Kotlin)放大缩小imageView

import android.os.Bundle
import android.view.GestureDetector
import android.view.MotionEvent
import android.widget.ImageView
import androidx.appcompat.app.AppCompatActivity

class MainActivity : AppCompatActivity() {

    private lateinit var imageView: ImageView
    private lateinit var gestureDetector: GestureDetector

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        imageView = findViewById(R.id.imageView)
        gestureDetector = GestureDetector(this, object : GestureDetector.SimpleOnGestureListener() {
            override fun onDoubleTap(e: MotionEvent?): Boolean {
                zoomImage(e?.x ?: 0f, e?.y ?: 0f)
                return true
            }
        })

        imageView.setOnTouchListener { _, event ->
            gestureDetector.onTouchEvent(event)
            true
        }
    }

    private fun zoomImage(x: Float, y: Float) {
        val scaleFactor = if (imageView.scaleType == ImageView.ScaleType.FIT_CENTER) 2.0f else 1.0f
        imageView.scaleType = ImageView.ScaleType.MATRIX
        val matrix = imageView.imageMatrix
        val centerX = imageView.width / 2f
        val centerY = imageView.height / 2f
        matrix.postScale(scaleFactor, scaleFactor, centerX, centerY)
        imageView.imageMatrix = matrix
    }
}