Android(安卓)背景虚化实现

需求：

弹出dialog或者其他一个页面，UI背景显示虚化。

注意：这里虚化并不等于暗化，暗化比较简单通过设置FLAG_DIM_BEHIND即可。

在Andorid 4.1 之前（SDK_INT <16），背景虚化可以使用FLAG_BLUR_BEHIND实现的，但是后续版本Android不再支持，因此才有这篇文章的做法。

解决方案：

step1：获取当前UI的bitmap

step2：将bitmap进行虚化处理

step3：将虚化的bitmap设置为背景即可

这里提供一个工具类，帮助完成前两步，最后一步虚化的bitmap怎么使用，就又使用者来决定了。

示例代码：

/**使用示例如下1. 直接调用BlurUtil的getBlurBackground即可，注意这里需要传入的是一个activity对象2. dialog注意要设置全屏才能达到显示效果，因为设置的是dialog背景*/public class MainActivity extends AppCompatActivity {    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        findViewById(R.id.textView).setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View v) {                //通过工具类，获取虚化的bitmap                Bitmap bitmap = BlurUtil.getBlurBackground(MainActivity.this);                //将虚化的bitmap 设置为背景                CustDialog dialog = new CustDialog(MainActivity.this, R.style.Dialog_Fullscreen, bitmap);                dialog.setTitle("blur behind dialog");                dialog.show();            }        });    }}

实际效果：

BlurUtil源码：

/**这是BlurUtil的源码，对外提供一个getBlurBackground的public方法。*/import android.app.Activity;import android.content.Context;import android.graphics.Bitmap;import android.os.Build.VERSION;import android.renderscript.Allocation;import android.renderscript.Element;import android.renderscript.RenderScript;import android.renderscript.ScriptIntrinsicBlur;import android.view.View;public class BlurUtil {public static Bitmap getBlurBackground(Activity activity) {Bitmap originBitmap = getBackground(activity);Bitmap blurBitmap = BlurUtil.apply(activity, originBitmap, 25);return blurBitmap;}private static Bitmap getBackground(Activity activity) {View decorView = activity.getWindow().getDecorView();decorView.setDrawingCacheQuality(View.DRAWING_CACHE_QUALITY_LOW);decorView.setDrawingCacheEnabled(true);decorView.buildDrawingCache();Bitmap image = decorView.getDrawingCache();return image;}private static Bitmap apply(Context context, Bitmap sentBitmap) {return apply(context, sentBitmap, 10);}private static Bitmap apply(Context context, Bitmap sentBitmap, int radius) {        Bitmap bitmap = Bitmap.createScaledBitmap(sentBitmap, sentBitmap.getWidth()/2, sentBitmap.getHeight()/2, false);if (VERSION.SDK_INT > 16) {final RenderScript rs = RenderScript.create(context);final Allocation input = Allocation.createFromBitmap(rs, bitmap, Allocation.MipmapControl.MIPMAP_NONE,Allocation.USAGE_SCRIPT);final Allocation output = Allocation.createTyped(rs, input.getType());final ScriptIntrinsicBlur script = ScriptIntrinsicBlur.create(rs, Element.U8_4(rs));script.setRadius(radius);script.setInput(input);script.forEach(output);output.copyTo(bitmap);                                                //After finishing everything, we destroy the Renderscript.                        rs.destroy();return bitmap;}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++) {// Preserve alpha channel: ( 0xff000000 & pix[yi] )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);}}

需求：

解决方案：

示例代码：

实际效果：

BlurUtil源码：

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