一 示例

二 代码

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <com.example.test.ui.video.ui.image.topfit.TopFitImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@color/purple_200"
        android:scaleType="fitXY" />

    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="largeWidthStretch"
            android:text="2/1宽高比" />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="equalWidthStretch"
            android:text="1/1宽高比" />
    </LinearLayout>

</FrameLayout>

package com.example.test.ui.video.ui.image.topfit

import android.content.Context
import android.graphics.Bitmap
import android.util.AttributeSet


class TopFitImageView : androidx.appcompat.widget.AppCompatImageView {
    constructor(context: Context?) : super(context!!)
    constructor(context: Context?, attrs: AttributeSet?) : super(context!!, attrs)
    constructor(context: Context?, attrs: AttributeSet?, defStyleAttr: Int) : super(
        context!!,
        attrs,
        defStyleAttr
    )

    val minWHRatio = 1
    val maxWHRatio = 2

    override fun onMeasure(widthMeasureSpec: Int, heightMeasureSpec: Int) {
        val drawable = drawable
        if (drawable != null) {
            val whRatio = drawable.intrinsicWidth.toFloat() / drawable.intrinsicHeight.toFloat()
            val width = MeasureSpec.getSize(widthMeasureSpec)
            var height = (width / whRatio).toInt()
            if (whRatio > maxWHRatio) {
                height = width / maxWHRatio
            } else if (whRatio < minWHRatio) {
                height = width
            }
            setMeasuredDimension(width, height)
        } else {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec)
        }
    }

    override fun setImageBitmap(bm: Bitmap?) {
        if (bm != null && bm.width > 0 && bm.height > 0) {
            var height = bm.height
            val whRatio = bm.width / bm.height
//            if (whRatio > maxWHRatio) {
//                height = bm.width / maxWHRatio
//            } else
            if (whRatio < minWHRatio) {
                height = bm.width
            }
            super.setImageBitmap(Bitmap.createBitmap(bm, 0, 0, bm.width, height))
            return
        }
        super.setImageBitmap(bm)
    }

}