android dialog背景模糊化效果实现方法

最近做项目有这样的需求: 在activity中启动一个dialog时, 启动的dialog的背景设为启动acitivity的模糊化图片.

实现思路:

1. 截屏, 获取当前activity的界面
2. 将获取的照片进行模糊化
3. 将模糊化的图片设为dialog的背景

1.截屏, 获取当前activity的界面

private Bitmap takeScreenShot(Activity activity) {
  View view = activity.getWindow().getDecorView();
  view.setDrawingCacheEnabled(true);
  view.buildDrawingCache();
  Bitmap b1 = view.getDrawingCache();

  // 获取屏幕长和高
  int width = activity.getResources().getDisplayMetrics().widthPixels;
  int height = activity.getResources().getDisplayMetrics().heightPixels;

  Bitmap bmp = Bitmap.createBitmap(b1, 0, 0, width, height);
  view.destroyDrawingCache();
  return bmp;
 }

这里需要注意: 默认dialog是全屏, activity也是全屏没有状态栏. 如果有状态栏需要获取状态栏大小, 在创建图片的时候减去状态栏大小.

2.将获取的图片进行模糊化, 这里的模糊算法, 是从网上查到, 具体是进行高斯模糊. 具体代码在下面的工具类中.

3.设置模糊图片为dialog的背景

//blurBackgroundDrawer为模糊后的背景图片
 Window window = getWindow();
 window.setBackgroundDrawable(new BitmapDrawable(mContext.getResources(), blurBackgroundDrawer));

注意: 模糊化图片可能会比较慢, 刚开始测得时候在3 - 4秒之间, 解决办法是将获取到的屏幕进行缩小,然后在进行模糊, 模糊完后, 再将图片放大.

下面是将背景模糊化效果封装成的工具类代码, 使用方法: 只需要将其考到工程中, 在需要模糊化效果的地方调用:
Bitmap bmp = getBlurBackgroundDrawer(activity); 即可.

public class FastBlurUtility {

 /**
  * 获得模糊化的背景图片
  * @param activity 获取模糊化的背景activity
  * @return 模糊化的背景图片
  */
 public static Bitmap getBlurBackgroundDrawer(Activity activity) {
  Bitmap bmp = takeScreenShot(activity);
  return startBlurBackground(bmp);
 }

 /**
  * 截屏
  * @param activity 截屏的activity
  * @return 截屏图片
  */
 private static Bitmap takeScreenShot(Activity activity) {
  View view = activity.getWindow().getDecorView();
  view.setDrawingCacheEnabled(true);
  view.buildDrawingCache();
  Bitmap b1 = view.getDrawingCache();

  // 获取屏幕长和高
  int width = activity.getResources().getDisplayMetrics().widthPixels;
  int height = activity.getResources().getDisplayMetrics().heightPixels;

  Bitmap bmp = Bitmap.createBitmap(b1, 0, 0, width, height);
  view.destroyDrawingCache();
  return bmp;
 }

 private static Bitmap startBlurBackground(Bitmap bkg) {
  long startMs = System.currentTimeMillis();
  float radius = 20; //模糊程度

  Bitmap overlay = fastblur(small(bkg), (int) radius);

  Log.i("FastBlurUtility", "=====blur time:" + (System.currentTimeMillis() - startMs));
  return big(overlay);
 }

 /**
  * 放大图片
  * @param bitmap 需要放大的图片
  * @return 放大的图片
  */
 private static Bitmap big(Bitmap bitmap) {
  Matrix matrix = new Matrix();
  matrix.postScale(4f, 4f);
  Bitmap resizeBmp = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
  return resizeBmp;
 }

 /**
  * 缩小图片
  * @param bitmap 需要缩小的图片
  * @return 缩小的图片
  */
 private static Bitmap small(Bitmap bitmap) {
  Matrix matrix = new Matrix();
  matrix.postScale(0.25f, 0.25f);
  Bitmap resizeBmp = Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, true);
  return resizeBmp;
 }

 /**
  * 将图片模糊化
  * @param sentBitmap 需要模糊的图片
  * @param radius  模糊程度
  * @return 模糊后的图片
  */
 private static Bitmap fastblur(Bitmap sentBitmap, int radius) {

  Bitmap bitmap = sentBitmap.copy(sentBitmap.getConfig(), true);

  if (radius < 1) {
   return (null);
  }

  int w = bitmap.getWidth();
  int h = bitmap.getHeight();

  int[] pix = new int[w * h];
  bitmap.getPixels(pix, 0, w, 0, 0, w, h);

  int wm = w - 1;
  int hm = h - 1;
  int wh = w * h;
  int div = radius + radius + 1;

  int r[] = new int[wh];
  int g[] = new int[wh];
  int b[] = new int[wh];
  int rsum, gsum, bsum, x, y, i, p, yp, yi, yw;
  int vmin[] = new int[Math.max(w, h)];

  int divsum = (div + 1) >> 1;
  divsum *= divsum;
  int dv[] = new int[256 * divsum];
  for (i = 0; i < 256 * divsum; i++) {
   dv[i] = (i / divsum);
  }

  yw = yi = 0;

  int[][] stack = new int[div][3];
  int stackpointer;
  int stackstart;
  int[] sir;
  int rbs;
  int r1 = radius + 1;
  int routsum, goutsum, boutsum;
  int rinsum, ginsum, binsum;

  for (y = 0; y < h; y++) {
   rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
   for (i = -radius; i <= radius; i++) {
    p = pix[yi + Math.min(wm, Math.max(i, 0))];
    sir = stack[i + radius];
    sir[0] = (p & 0xff0000) >> 16;
    sir[1] = (p & 0x00ff00) >> 8;
    sir[2] = (p & 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];
    }
   }
   stackpointer = radius;

   for (x = 0; x < w; x++) {

    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 & 0xff0000) >> 16;
    sir[1] = (p & 0x00ff00) >> 8;
    sir[2] = (p & 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++;
   }
   yw += w;
  }
  for (x = 0; x < w; x++) {
   rinsum = ginsum = binsum = routsum = goutsum = boutsum = rsum = gsum = bsum = 0;
   yp = -radius * w;
   for (i = -radius; i <= radius; i++) {
    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;
    }
   }
   yi = x;
   stackpointer = radius;
   for (y = 0; y < h; y++) {
    pix[yi] = (0xff000000 & pix[yi]) | (dv[rsum] << 16) | (dv[gsum] << 8) | 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;
   }
  }

  bitmap.setPixels(pix, 0, w, 0, 0, w, h);

  return (bitmap);
 }
}

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