View-＞Bitmap缩放到自定义ViewGroup的任意区域(Matrix方式绘制Bitmap)-Activity代码

const val TAG = "Yang"
class MainActivity : AppCompatActivity() {
    var mRealView : MyImageView ?= null
    var mRelativeLayout : MyRelativeLayout ?= null
    var tempBitmap : Bitmap ?= null
    var mHandler = Handler(Looper.getMainLooper())
    var screenWidth = 0
    var screenHeight = 0
    var srcRect = RectF()
    var destRect = RectF()
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        mRealView = findViewById(R.id.real_iv)
        mRelativeLayout = findViewById(R.id.real_rl)
        // 屏幕宽高的一半作为临时RectF, 用于压缩Bitmap
        screenWidth = resources.displayMetrics.widthPixels
        screenHeight = resources.displayMetrics.heightPixels
        val tempRect = RectF(0f, 0f, screenWidth.toFloat() / 2, screenHeight.toFloat() / 2)
        
        
        CoroutineScope(Dispatchers.IO).launch {
            tempBitmap = getBitmap(resources, tempRect, R.drawable.fake)
            withContext(Dispatchers.Main) {
                mRelativeLayout?.post {
                    // 获取初始区域的RectF
                    srcRect.set(
                        0f,
                        0f,
                        mRelativeLayout?.width?.toFloat()!!,
                        mRelativeLayout?.height?.toFloat()!!
                    )
                    // 获取结束区域的RectF
                    mRelativeLayout?.forEach { childView ->
                        if (childView is MyImageView) {
                            destRect.set(
                                0f,
                                0f,
                                 childView.width.toFloat(),
                                childView.height.toFloat()
                            )
                        }
                    }
                    scaleRectFun(tempBitmap, srcRect, destRect)
                }
            }
        }
    }
    
    fun scaleRectFun(tempBitmap: Bitmap?, srcRect : RectF, destRect: RectF){
        tempBitmap?.let { bitmap->
            mRelativeLayout?.setBitmap(bitmap)
            val animator = ValueAnimator.ofFloat(0f, 1f)
            animator.duration = 5000L
            animator.interpolator = DecelerateInterpolator()
            animator.addUpdateListener {
                val value = it.animatedValue as Float
                // 中心缩放
                mRelativeLayout?.setDestRectCenterWithTranslate(srcRect, destRect, value)
                // 左上角不带平移缩放
                // mRelativeLayout?.setDestRectLeftTopNoTranslate(srcRect, destRect, value)
                // 左上角平移缩放
                // mRelativeLayout?.setDestRectLeftTopWithTranslate(srcRect, destRect, value)
                // 右上角不带平移缩放
                // mRelativeLayout?.setDestRectRightTopNoTranslate(srcRect, destRect, value)
                // 右上角平移缩放
                // mRelativeLayout?.setDestRectRightTopWithTranslate(srcRect, destRect, value)
                // 左下角不带平移缩放
                // mRelativeLayout?.setDestRectLeftBottomNoTranslate(srcRect, destRect, value)
                // 左下角平移缩放
                // mRelativeLayout?.setDestRectLeftBottomWithTranslate(srcRect, destRect, value)
                // 右下角不带平移缩放
                // mRelativeLayout?.setDestRectRightBottomNoTranslate(srcRect, destRect, value)
                // 右下角平移缩放
                // mRelativeLayout?.setDestRectRightBottomWithTranslate(srcRect, destRect, value)
            }
            animator.start()
        }
    }
}
fun getBitmap(resources : Resources, destRect : RectF, imageId: Int): Bitmap? {
    var imageWidth = -1
    var imageHeight = -1
    val preOption = BitmapFactory.Options().apply {
        // 只获取图片的宽高
        inJustDecodeBounds = true
        BitmapFactory.decodeResource(resources, imageId, this)
    }
    imageWidth = preOption.outWidth
    imageHeight = preOption.outHeight
    // 计算缩放比例
    val scaleMatrix = Matrix()
    // 确定未缩放Bitmap的RectF
    var srcRect = RectF(0f, 0f, imageWidth.toFloat(), imageHeight.toFloat())
    // 通过目标RectF, 确定缩放数值，存储在scaleMatrix中
    scaleMatrix.setRectToRect(srcRect, destRect, Matrix.ScaleToFit.CENTER)
    // 缩放数值再映射到原始Bitmap上，得到缩放后的RectF
    scaleMatrix.mapRect(srcRect)

    val finalOption = BitmapFactory.Options().apply {
        if (imageHeight > 0 && imageWidth > 0) {
            inPreferredConfig = Bitmap.Config.RGB_565
            inSampleSize = calculateInSampleSize(
                imageWidth,
                imageHeight,
                srcRect.width().toInt(),
                srcRect.height().toInt()
            )
        }
    }
    return BitmapFactory.decodeResource(resources, imageId, finalOption)
}

fun calculateInSampleSize(fromWidth: Int, fromHeight: Int, toWidth: Int, toHeight: Int): Int {
    var bitmapWidth = fromWidth
    var bitmapHeight = fromHeight
    if (fromWidth > toWidth|| fromHeight > toHeight) {
        var inSampleSize = 2
        // 计算最大的inSampleSize值，该值是2的幂，并保持原始宽高大于目标宽高
        while (bitmapWidth >= toWidth && bitmapHeight >= toHeight) {
            bitmapWidth /= 2
            bitmapHeight /= 2
            inSampleSize *= 2
        }
        return inSampleSize
    }
    return 1
}