Android 背景虚化

首先是生成背景的Bitmap：

    private Bitmap createViewBitmap(View view) {
        view.setDrawingCacheEnabled(true);
        view.buildDrawingCache();
        Bitmap bitmap = view.getDrawingCache();
        Bitmap cacheBitmap = null;
        if (bitmap != null)
            cacheBitmap = Bitmap.createBitmap(bitmap);
        view.destroyDrawingCache();
        view.setDrawingCacheEnabled(false);
        return cacheBitmap;
    }

其次是将Bitmap进行虚化：
其中的setRadius最大只能设置为25，否则报错，len是进行虚化的次数，设置16是这个效果比较适合项目。

    private Bitmap blurBitmap(Bitmap bitmap) {
        if (bitmap != null) {
            mRenderScript = RenderScript.create(mContext);
            Bitmap outBitmap = Bitmap.createBitmap(bitmap, 0, 0,
                    bitmap.getWidth(), bitmap.getHeight());
            int len = 16;
            for (int i = 0; i < len; i++) {
                ScriptIntrinsicBlur scriptIntrinsicBlur =
                        ScriptIntrinsicBlur.create(mRenderScript, Element.U8_4(mRenderScript));
                final Allocation inAllocation =
                        Allocation.createFromBitmap(mRenderScript, bitmap),
                        outAllocation = Allocation.createFromBitmap(mRenderScript, outBitmap);
                scriptIntrinsicBlur.setRadius(25);
                scriptIntrinsicBlur.setInput(inAllocation);
                scriptIntrinsicBlur.forEach(outAllocation);
                outAllocation.copyTo(outBitmap);
                bitmap.recycle();
                bitmap = Bitmap.createBitmap(outBitmap, 0, 0,
                        outBitmap.getWidth(), outBitmap.getHeight());
            }
            mRenderScript.destroy();
            mRenderScript = null;
            return outBitmap;
        }
        return null;
    }

将生成的Bitmap保存到本地，下次就不用再重新虚化了：

        try {
            File photoDir = new File(Environment.getExternalStorageDirectory() + "/ima g");
            photoDir.mkdir();
            File file = new File(photoDir, "home_page_dialog_background.png");
            Log.d("tag",file.getPath());
            file.createNewFile();
            FileOutputStream fos = new FileOutputStream(file);
            mDialogBackground.compress(Bitmap.CompressFormat.PNG,100, fos);
            fos.flush();
            fos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }