Android用setRectToRect实现Bitmap基于Matrix矩阵scale缩放RectF动画，Kotlin（二）

 

文章 https://zhangphil.blog.csdn.net/article/details/135980821 实现了基于Matrix缩放Bitmap的动画，但是从左上角（0,0）位置开始的，现在实现从中心点位置开始缩放：

 

<?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:background="@android:color/darker_gray"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <ImageView
        android:id="@+id/iv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true"
        android:src="@mipmap/mypic" />

    <ImageView
        android:id="@+id/result"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

 

 

import android.graphics.Bitmap
import android.graphics.Canvas
import android.graphics.Color
import android.graphics.Matrix
import android.graphics.RectF
import android.graphics.drawable.BitmapDrawable
import android.os.Bundle
import android.widget.ImageView
import androidx.appcompat.app.AppCompatActivity
import kotlinx.coroutines.CoroutineScope
import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.delay
import kotlinx.coroutines.launch
import kotlinx.coroutines.withContext


class MainActivity : AppCompatActivity() {
    private var mSrcImageView: ImageView? = null
    private var result: ImageView? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)
        mSrcImageView = findViewById(R.id.iv)
        result = findViewById(R.id.result)
    }

    override fun onResume() {
        super.onResume()

        result?.postDelayed({
            val srcBmp = (mSrcImageView?.drawable as BitmapDrawable).bitmap
            matrixAnimScale(srcBmp)
        }, 800)
    }

    private fun matrixAnimScale(srcBmp: Bitmap) {
        val delayTime = 1L //动画之间的间隔。
        val step = 100f //100次缩放绘制，每步延时delayTime毫秒，总计 delayTime*step 毫秒完成动画。

        val deltaW: Float = mSrcImageView!!.width / step
        val deltaH: Float = mSrcImageView!!.height / step

        CoroutineScope(Dispatchers.IO).launch {
            var w = 0f
            var h = 0f

            for (i in 0 until step.toInt()) {
                delay(delayTime)

                w += deltaW
                h += deltaH

                val bmp = Bitmap.createBitmap(mSrcImageView!!.width, mSrcImageView!!.height, Bitmap.Config.ARGB_8888)
                val c = Canvas(bmp)
                c.drawColor(Color.BLUE)

                val src = RectF(0f, 0f, srcBmp.width.toFloat(), srcBmp.height.toFloat())
                val dst = RectF(0f, 0f, w, h)

                val mx = Matrix()
                mx.setRectToRect(src, dst, Matrix.ScaleToFit.CENTER)
                //移动矩阵到中心位置点缩放。
                mx.postTranslate(mSrcImageView!!.width / 2f - dst.width() / 2f, mSrcImageView!!.height / 2f - dst.height() / 2f)

                c.drawBitmap(srcBmp, mx, null)

                withContext(Dispatchers.Main) {
                    result?.setImageBitmap(bmp)
                }
            }
        }
    }
}

 

开始从中心点缩放：

 

 

 

逐渐变大：

 

 

变大过程：

 

 

最终：

 

 

 

https://zhangphil.blog.csdn.net/article/details/135980821