android - How set bitmap or drawable in screen, when app go in background

Question

When I minimize the application, I need the picture to be installed on the screen (foreground) - as soon as I minimize it. Now I'm trying to call the method for setting the picture in Activity onStop, but the installation occurs after the application is restored. How to make the picture be installed immediately when minimized?

In the example below, the screen goes from normal (user active - onResume) to blurred (go to background - onStop).

UPDATED: See code here:

// Class for generate blur screen (as screenshot)

class BlurScreenSetter {

fun addView(view: View) {
    val bitmap = takeScreenshot(view)
    val blur = fastblur(bitmap!!, 50)
    view.foreground = blur?.toDrawable(view.resources)
}

private fun takeScreenshot(view: View): Bitmap? {
    val bitmap = Bitmap.createBitmap(view.width, view.height, Bitmap.Config.ARGB_8888)
    val canvas = Canvas(bitmap)
    view.draw(canvas)
    return bitmap
}

private fun fastblur(sentBitmap: Bitmap, radius: Int): Bitmap? {
    val bitmap = sentBitmap.copy(sentBitmap.config, true)
    if (radius < 1) {
        return null
    }
    val w = bitmap.width
    val h = bitmap.height
    val pix = IntArray(w * h)

    bitmap.getPixels(pix, 0, w, 0, 0, w, h)
    val wm = w - 1
    val hm = h - 1
    val wh = w * h
    val div = radius + radius + 1
    val r = IntArray(wh)
    val g = IntArray(wh)
    val b = IntArray(wh)
    var rsum: Int
    var gsum: Int
    var bsum: Int
    var x: Int
    var y: Int
    var i: Int
    var p: Int
    var yp: Int
    var yi: Int
    var yw: Int
    val vmin = IntArray(Math.max(w, h))
    var divsum = div + 1 shr 1
    divsum *= divsum
    val dv = IntArray(256 * divsum)
    i = 0
    while (i < 256 * divsum) {
        dv[i] = i / divsum
        i++
    }
    yi = 0
    yw = yi
    val stack = Array(div) { IntArray(3) }
    var stackpointer: Int
    var stackstart: Int
    var sir: IntArray
    var rbs: Int
    val r1 = radius + 1
    var routsum: Int
    var goutsum: Int
    var boutsum: Int
    var rinsum: Int
    var ginsum: Int
    var binsum: Int
    y = 0
    while (y < h) {
        bsum = 0
        gsum = bsum
        rsum = gsum
        boutsum = rsum
        goutsum = boutsum
        routsum = goutsum
        binsum = routsum
        ginsum = binsum
        rinsum = ginsum
        i = -radius
        while (i <= radius) {
            p = pix[yi + Math.min(wm, Math.max(i, 0))]
            sir = stack[i + radius]
            sir[0] = p and 0xff0000 shr 16
            sir[1] = p and 0x00ff00 shr 8
            sir[2] = p and 0x0000ff
            rbs = r1 - Math.abs(i)
            rsum += sir[0] * rbs
            gsum += sir[1] * rbs
            bsum += sir[2] * rbs
            if (i > 0) {
                rinsum += sir[0]
                ginsum += sir[1]
                binsum += sir[2]
            } else {
                routsum += sir[0]
                goutsum += sir[1]
                boutsum += sir[2]
            }
            i++
        }
        stackpointer = radius
        x = 0
        while (x < w) {
            r[yi] = dv[rsum]
            g[yi] = dv[gsum]
            b[yi] = dv[bsum]
            rsum -= routsum
            gsum -= goutsum
            bsum -= boutsum
            stackstart = stackpointer - radius + div
            sir = stack[stackstart % div]
            routsum -= sir[0]
            goutsum -= sir[1]
            boutsum -= sir[2]
            if (y == 0) {
                vmin[x] = Math.min(x + radius + 1, wm)
            }
            p = pix[yw + vmin[x]]
            sir[0] = p and 0xff0000 shr 16
            sir[1] = p and 0x00ff00 shr 8
            sir[2] = p and 0x0000ff
            rinsum += sir[0]
            ginsum += sir[1]
            binsum += sir[2]
            rsum += rinsum
            gsum += ginsum
            bsum += binsum
            stackpointer = (stackpointer + 1) % div
            sir = stack[stackpointer % div]
            routsum += sir[0]
            goutsum += sir[1]
            boutsum += sir[2]
            rinsum -= sir[0]
            ginsum -= sir[1]
            binsum -= sir[2]
            yi++
            x++
        }
        yw += w
        y++
    }
    x = 0
    while (x < w) {
        bsum = 0
        gsum = bsum
        rsum = gsum
        boutsum = rsum
        goutsum = boutsum
        routsum = goutsum
        binsum = routsum
        ginsum = binsum
        rinsum = ginsum
        yp = -radius * w
        i = -radius
        while (i <= radius) {
            yi = Math.max(0, yp) + x
            sir = stack[i + radius]
            sir[0] = r[yi]
            sir[1] = g[yi]
            sir[2] = b[yi]
            rbs = r1 - Math.abs(i)
            rsum += r[yi] * rbs
            gsum += g[yi] * rbs
            bsum += b[yi] * rbs
            if (i > 0) {
                rinsum += sir[0]
                ginsum += sir[1]
                binsum += sir[2]
            } else {
                routsum += sir[0]
                goutsum += sir[1]
                boutsum += sir[2]
            }
            if (i < hm) {
                yp += w
            }
            i++
        }
        yi = x
        stackpointer = radius
        y = 0
        while (y < h) {

            // Preserve alpha channel: ( 0xff000000 & pix[yi] )
            pix[yi] = -0x1000000 and pix[yi] or (dv[rsum] shl 16) or (dv[gsum] shl 8) or dv[bsum]
            rsum -= routsum
            gsum -= goutsum
            bsum -= boutsum
            stackstart = stackpointer - radius + div
            sir = stack[stackstart % div]
            routsum -= sir[0]
            goutsum -= sir[1]
            boutsum -= sir[2]
            if (x == 0) {
                vmin[y] = Math.min(y + r1, hm) * w
            }
            p = x + vmin[y]
            sir[0] = r[p]
            sir[1] = g[p]
            sir[2] = b[p]
            rinsum += sir[0]
            ginsum += sir[1]
            binsum += sir[2]
            rsum += rinsum
            gsum += ginsum
            bsum += binsum
            stackpointer = (stackpointer + 1) % div
            sir = stack[stackpointer]
            routsum += sir[0]
            goutsum += sir[1]
            boutsum += sir[2]
            rinsum -= sir[0]
            ginsum -= sir[1]
            binsum -= sir[2]
            yi += w
            y++
        }
        x++
    }
    bitmap.setPixels(pix, 0, w, 0, 0, w, h)
    return bitmap
}

}

// Observe in custom Application class

in onCreate

registerActivityLifecycleCallbacks(object : ActivityLifecycleCallbacks {

override fun onActivityPaused(activity: Activity) {
                BlurScreenSetter().addView((activity as AppCompatActivity).window.decorView)
            }

            override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {}
            override fun onActivityStarted(activity: Activity) {}
            override fun onActivityResumed(activity: Activity) {}
            override fun onActivityStopped(activity: Activity) {}
            override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {}
            override fun onActivityDestroyed(activity: Activity) {}

question from:https://stackoverflow.com/questions/65651236/how-set-bitmap-or-drawable-in-screen-when-app-go-in-background

Answer 1

If you. want hide the content of screen use this flag before setContentView()

getWindow().addFlags(WindowManager.LayoutParams.FLAG_SECURE);

For custom bitmap --> Use your own logic.

place ImageView when onPause() when onResume() hide that imageView