RecyclerView 截屏

截取整個RecyclerView的，使其是一張完整的圖檔。思路就是調用每個ItemView的setDrawingCacheEnabled(true)方法，通過View的getDrawingCache()獲得Bitmap，然後把這些ItemView 産生的Bitmap儲存起來，然後，把這些小的Bitmap整合成一張的大Bitmap。

public static Bitmap shotRecyclerView(RecyclerView view) {
    RecyclerView.Adapter adapter = view.getAdapter();
    Bitmap bigBitmap = null;
    if (adapter != null) {
        int size = adapter.getItemCount();
        int height = 0;
        Paint paint = new Paint();
        int iHeight = 0;
        final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / 1024);
        // Use 1/8th of the available memory for this memory cache.
        final int cacheSize = maxMemory / 8;
        //這個地方用LruCache顯得高大上，實際上用個List也是可以的
        LruCache<String, Bitmap> bitmapCache = new LruCache<>(cacheSize);
        for (int i = 0; i < size; i++) {
            RecyclerView.ViewHolder holder = adapter.createViewHolder(view, adapter.getItemViewType(i));
            adapter.onBindViewHolder(holder, i);
            holder.itemView.measure(
                    View.MeasureSpec.makeMeasureSpec(view.getWidth(), View.MeasureSpec.EXACTLY),
                    View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));
            holder.itemView.layout(0, 0, holder.itemView.getMeasuredWidth(),
                    holder.itemView.getMeasuredHeight());
            holder.itemView.setDrawingCacheEnabled(true);
            holder.itemView.buildDrawingCache();
            Bitmap drawingCache = holder.itemView.getDrawingCache();
            if (drawingCache != null) {
                bitmapCache.put(String.valueOf(i), drawingCache);
            }
            height += holder.itemView.getMeasuredHeight();
        }
        // 這個地方容易出現OOM，關鍵是要看截取RecyclerView的展開的寬高
        bigBitmap = Bitmap.createBitmap(view.getMeasuredWidth(), height, Bitmap.Config.ARGB_8888);
        Canvas bigCanvas = new Canvas(bigBitmap);
        Drawable lBackground = view.getBackground();
        //先畫RecyclerView的背景色
        if (lBackground instanceof ColorDrawable) {
            ColorDrawable lColorDrawable = (ColorDrawable) lBackground;
            int lColor = lColorDrawable.getColor();
            bigCanvas.drawColor(lColor);
        }
        for (int i = 0; i < size; i++) {
            Bitmap bitmap = bitmapCache.get(String.valueOf(i));
            bigCanvas.drawBitmap(bitmap, 0f, iHeight, paint);
            iHeight += bitmap.getHeight();
            bitmap.recycle();
        }
    }
    return bigBitmap;
}