Android毛半透明效果側滑菜單

Android毛半透明效果側滑菜單
實現目標相信大家都知道毛半透明效果是怎樣的，也可以說是高斯模糊效果。如下：
這是一個透明，且會對背景進行高斯模糊的效果，看起來就像是毛玻璃一樣，其實不光是側滑菜單，只要是view，理論上都可以實現這樣的效果，接下來我們就來實現這個效果。第一步：架構搭建我使用的android studio，所以要建立這樣一個帶側滑菜單的項目非常簡單，在建立項目的步驟中，執行到這一步，選擇Navigation Drawer Activity就可以了：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"brush:java;">mNavigationDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager().findFragmentById(R.id.navigation_drawer);這個NavigationDrawerFragment就是我們的側滑菜單實現的類，可以不去管它。然後需要擷取到這個Fragment中的View，擷取View的觀察者並且註冊PreDraw監聽事件：

mNavigationDrawerFragment.getView().getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {                    });

這個OnPreDrawListener需要實現OnPreDraw方法，就在這個方法中，對當前的View，進行，並且高斯模糊。首先找到根控制項，並建立一個Bitmap對象來儲存。

private FrameLayout view;private Bitmap bitmap;

對view初始化後，開始對view進行，對view的方式如下：

view.buildDrawingCache();bitmap = view.getDrawingCache();

這樣，bitmap中就儲存了當前的view的，接下來我們要對圖片進行高斯模糊，關於高斯模糊的演算法，網上有很多，我就隨便貼一個（複製來的）：

    public static Bitmap doBlur(Bitmap sentBitmap, int radius, boolean canReuseInBitmap) {        // Stack Blur v1.0 from        // http://www.quasimondo.com/StackBlurForCanvas/StackBlurDemo.html        //        // Java Author: Mario Klingemann         // http://incubator.quasimondo.com        // created Feburary 29, 2004        // Android port : Yahel Bouaziz         // http://www.kayenko.com        // ported april 5th, 2012        // This is a compromise between Gaussian Blur and Box blur        // It creates much better looking blurs than Box Blur, but is        // 7x faster than my Gaussian Blur implementation.        //        // I called it Stack Blur because this describes best how this        // filter works internally: it creates a kind of moving stack        // of colors whilst scanning through the image. Thereby it        // just has to add one new block of color to the right side        // of the stack and remove the leftmost color. The remaining        // colors on the topmost layer of the stack are either added on        // or reduced by one, depending on if they are on the right or        // on the left side of the stack.        //        // If you are using this algorithm in your code please add        // the following line:        //        // Stack Blur Algorithm by Mario Klingemann         Bitmap bitmap;        if (canReuseInBitmap) {            bitmap = sentBitmap;        } else {            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++) {                // 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);    }

第一個參數為需要高斯模糊的圖片，第二個參數可以理解為模糊效果大小，第三個參數表示位元影像是否可以重複使用。好了，有了處理好的圖片，就可以設定到Drawer的背景裡了。。。。真的嗎？仔細一想，當然不對，現在截的圖是整個view的圖，而我們的Drawer是慢慢側滑出來的，隨時都可能停止，所以，使用完整的圖肯定是不行的。那麼就需要計算出截取view的圖片的位置，和設定到Drawer的位置，具體可以參考：
從圖上可以看的出來，其中需要的參數都是有聯絡的，也就是說，只要能得到其中的一個參數，其他的就能同時拿到了。Drawer的寬度可以定死，例子中定的是240，現在就只需要擷取到側滑到哪一個位置就能夠算出所有的參數。在View中，有這樣一個方法，叫做getLocationInWindow，可以擷取到當前View在整個Window中的位置，可以想象的到，擷取到的肯定是一個負數，通過Drawer的寬度和這個負數，可以很簡單的算出來顯示的寬度。（View中除了getLocationInWindow，還有很多其他的方法，擷取相對於各種視圖的位置，大家可以研究一下）。
首先擷取到位置：

int[] location = new int[2];mNavigationDrawerFragment.getView().getLocationInWindow(location);blur(bitmap, listView, location[0]);//只傳x座標

blur函數就是我們處理位置的細節了，傳的listView是Fragment裡的唯一一個view：

    private void blur(Bitmap bkg, View view,int width) {        float scaleFactor = 4;//縮放圖片，縮放之後模糊效果更好        float radius = 2;        Bitmap overlay = Bitmap.createBitmap((int) (view.getMeasuredWidth()/scaleFactor),                (int) (view.getMeasuredHeight()/scaleFactor), Bitmap.Config.ARGB_8888);        Canvas canvas = new Canvas(overlay);        canvas.translate(-view.getLeft()/scaleFactor, -view.getTop()/scaleFactor);        canvas.scale(1 / scaleFactor, 1 / scaleFactor);        Paint paint = new Paint();        paint.setFlags(Paint.FILTER_BITMAP_FLAG);        float visibleWidth = slideMenuWidth +width;//可見寬        int visibleHeight = view.getHeight();//可見高        //從view的中截取的地區，+10和下面-10的原因是，高斯模糊的邊有時會有黑影，所以增大模糊地區        Rect src = new Rect(0,0, (int)(visibleWidth)+10, visibleHeight);                RectF dest = new RectF(-width - 10, 0, slideMenuWidth, visibleHeight);//設定Drawer背景的地區                        canvas.drawBitmap(bkg, src, dest, paint);                overlay = ImageUtils.doBlur(overlay, (int)radius, true);//進行高斯模糊操作                if (Build.VERSION.SDK_INT < 16) {//16level以前使用這個方法，在16中被廢棄                                 view.setBackgroundDrawable(new BitmapDrawable(getResources(), overlay));                } else {                        view.setBackground(new BitmapDrawable(getResources(), overlay));                }        }

整個的事件監聽代碼如下：

mNavigationDrawerFragment.getView().getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {            @Override            public boolean onPreDraw() {                if (bitmap == null) {                    view.buildDrawingCache();                    bitmap = view.getDrawingCache();                }                int[] location = new int[2];                mNavigationDrawerFragment.getView().getLocationInWindow(location);                blur(bitmap, listView, location[0]);//只傳x座標                return true;            }        });

到這裡，側滑菜單的毛半透明效果就已經完成了。結語如果能夠理解我上面使用的方法，我相信大家一定能夠舉一反三，實現所有view的毛半透明效果，這個例子的代碼，我會放到github上，這裡就是連結地址：https://github.com/xjyaikj/GlassSlideMenuSample，如果代碼有什麼不對，或者值得最佳化的地方，非常希望您能跟我交流，我的連絡方式在左邊設定檔的下面。