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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