Android滚动截屏，ScrollView截屏

在做分享功能的时候，需要截取全屏内容，一屏展示不完的内容，一般我们会用到 ListView ，ScrollView或Recyclerview

一： 普通截屏的实现

获取当前Window 的 DrawingCache 的方式，即decorView的DrawingCache

  /**
   * shot the current screen ,with the status but the status is trans *
   *
   * @param ctx current activity
   */
  public static Bitmap shotActivity(Activity ctx) {

    View view = ctx.getWindow().getDecorView();
    view.setDrawingCacheEnabled(true);
    view.buildDrawingCache();

    Bitmap bp = Bitmap.createBitmap(view.getDrawingCache(), , , view.getMeasuredWidth(),
        view.getMeasuredHeight());

    view.setDrawingCacheEnabled(false);
    view.destroyDrawingCache();

    return bp;
  }

获取当前View的DrawingCache

   public static Bitmap getViewBp(View v) {
        if (null == v) {
            return null;
        }
        v.setDrawingCacheEnabled(true);
        v.buildDrawingCache();
        if (Build.VERSION.SDK_INT >= ) {
            v.measure(MeasureSpec.makeMeasureSpec(v.getWidth(),
                    MeasureSpec.EXACTLY), MeasureSpec.makeMeasureSpec(
                    v.getHeight(), MeasureSpec.EXACTLY));
            v.layout((int) v.getX(), (int) v.getY(),
                    (int) v.getX() + v.getMeasuredWidth(),
                    (int) v.getY() + v.getMeasuredHeight());
        } else {
            v.measure(MeasureSpec.makeMeasureSpec(, MeasureSpec.UNSPECIFIED),
                    MeasureSpec.makeMeasureSpec(, MeasureSpec.UNSPECIFIED));
            v.layout(, , v.getMeasuredWidth(), v.getMeasuredHeight());
        }
        Bitmap b = Bitmap.createBitmap(v.getDrawingCache(), , , v.getMeasuredWidth(), v.getMeasuredHeight());

        v.setDrawingCacheEnabled(false);
        v.destroyDrawingCache();
        return b;
    }

二：开源方案

在滚动视图中，如果当前View并没有在视图中全部绘制出来，我们可以利用View的ScrollTo()和ScrollBy()方法来移动画布，同时获取当前View的可视部分的DrawingCache，最后进行拼接得到其Bitmap，参考:PGSSoft/scrollscreenshot@[Github]，原理图如下：

三： ScrollView截屏

三个截屏中，ScrollView最简单，因为ScrollView只有一个childView，虽然没有全部显示在界面上，但是已经全部渲染绘制，因此可以直接 调用`scrollView.draw(canvas)`来完成截图，

  /**
   * http://blog.csdn.net/lyy1104/article/details/40048329
   */
  public static Bitmap shotScrollView(ScrollView scrollView) {
    int h = ;
    Bitmap bitmap = null;
    for (int i = ; i < scrollView.getChildCount(); i++) {
      h += scrollView.getChildAt(i).getHeight();
      scrollView.getChildAt(i).setBackgroundColor(Color.parseColor("#ffffff"));
    }
    bitmap = Bitmap.createBitmap(scrollView.getWidth(), h, Bitmap.Config.RGB_565);
    final Canvas canvas = new Canvas(bitmap);
    scrollView.draw(canvas);
    return bitmap;
  }

四： ListView截屏

而ListView就是会回收与重用Item，并且只会绘制在屏幕上显示的ItemView，根据stackoverflow上大神的建议，采用一个List来存储Item的视图，这种方案依然不够好，当Item足够多的时候，可能会发生oom。

/**
   * http://stackoverflow.com/questions/12742343/android-get-screenshot-of-all-listview-items
   */
  public static Bitmap shotListView(ListView listview) {

    ListAdapter adapter = listview.getAdapter();
    int itemscount = adapter.getCount();
    int allitemsheight = ;
    List<Bitmap> bmps = new ArrayList<Bitmap>();

    for (int i = ; i < itemscount; i++) {

      View childView = adapter.getView(i, null, listview);
      childView.measure(
          View.MeasureSpec.makeMeasureSpec(listview.getWidth(), View.MeasureSpec.EXACTLY),
          View.MeasureSpec.makeMeasureSpec(, View.MeasureSpec.UNSPECIFIED));

      childView.layout(, , childView.getMeasuredWidth(), childView.getMeasuredHeight());
      childView.setDrawingCacheEnabled(true);
      childView.buildDrawingCache();
      bmps.add(childView.getDrawingCache());
      allitemsheight += childView.getMeasuredHeight();
    }

    Bitmap bigbitmap =
        Bitmap.createBitmap(listview.getMeasuredWidth(), allitemsheight, Bitmap.Config.ARGB_8888);
    Canvas bigcanvas = new Canvas(bigbitmap);

    Paint paint = new Paint();
    int iHeight = ;

    for (int i = ; i < bmps.size(); i++) {
      Bitmap bmp = bmps.get(i);
      bigcanvas.drawBitmap(bmp, , iHeight, paint);
      iHeight += bmp.getHeight();

      bmp.recycle();
      bmp = null;
    }

    return bigbitmap;
  }

五： RecyclerView截屏

我们都知道，在新的Android版本中，已经可以用RecyclerView来代替使用ListView的场景，相比较ListView，RecyclerView对Item View的缓存支持的更好。可以采用和ListView相同的方案，这里也是在stackoverflow上看到的方案。

/**
   * https://gist.github.com/PrashamTrivedi/809d2541776c8c141d9a
   */
  public static Bitmap shotRecyclerView(RecyclerView view) {
    RecyclerView.Adapter adapter = view.getAdapter();
    Bitmap bigBitmap = null;
    if (adapter != null) {
      int size = adapter.getItemCount();
      int height = ;
      Paint paint = new Paint();
      int iHeight = ;
      final int maxMemory = (int) (Runtime.getRuntime().maxMemory() / );

      // Use 1/8th of the available memory for this memory cache.
      final int cacheSize = maxMemory / ;
      LruCache<String, Bitmap> bitmaCache = new LruCache<>(cacheSize);
      for (int i = ; 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(, View.MeasureSpec.UNSPECIFIED));
        holder.itemView.layout(, , holder.itemView.getMeasuredWidth(),
            holder.itemView.getMeasuredHeight());
        holder.itemView.setDrawingCacheEnabled(true);
        holder.itemView.buildDrawingCache();
        Bitmap drawingCache = holder.itemView.getDrawingCache();
        if (drawingCache != null) {

          bitmaCache.put(String.valueOf(i), drawingCache);
        }
        height += holder.itemView.getMeasuredHeight();
      }

      bigBitmap = Bitmap.createBitmap(view.getMeasuredWidth(), height, Bitmap.Config.ARGB_8888);
      Canvas bigCanvas = new Canvas(bigBitmap);
      Drawable lBackground = view.getBackground();
      if (lBackground instanceof ColorDrawable) {
        ColorDrawable lColorDrawable = (ColorDrawable) lBackground;
        int lColor = lColorDrawable.getColor();
        bigCanvas.drawColor(lColor);
      }

      for (int i = ; i < size; i++) {
        Bitmap bitmap = bitmaCache.get(String.valueOf(i));
        bigCanvas.drawBitmap(bitmap, 0f, iHeight, paint);
        iHeight += bitmap.getHeight();
        bitmap.recycle();
      }
    }
    return bigBitmap;
  }

六： 其他屏幕相关工具

1.获取状态来高度常见方式

 /**
     * get the height of status *
     */
    public static int getStatusH(Activity ctx) {
        Rect s = new Rect();
        ctx.getWindow().getDecorView().getWindowVisibleDisplayFrame(s);
        return s.top;
    }

 /**
     * get the height of status *
     */
    public static int getStatusH(Context ctx) {
        int statusHeight = -;
        try {
            Class<?> clazz = Class.forName("com.android.internal.R$dimen");
            Object object = clazz.newInstance();
            int height = Integer.parseInt(clazz.getField("status_bar_height")
                    .get(object).toString());
            statusHeight = ctx.getResources().getDimensionPixelSize(height);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return statusHeight;
    }

    /**
     * get the height of status *
     */
    public static int getStatusHeight(Activity activity) {
        int resourceId = activity.getResources().getIdentifier("status_bar_height", "dimen", "android");
        return resourceId >  ? activity.getResources().getDimensionPixelSize(resourceId) : ;
    }

2.获取标题栏高度

 /**
     * get the height of title *
     */
    public static int getTitleH(Activity ctx) {
        int contentTop = ctx.getWindow()
                .findViewById(Window.ID_ANDROID_CONTENT).getTop();
        return contentTop - getStatusH(ctx);
    }

3.获取屏幕宽高

 /**
     * get the width of screen **
     */
    public static int getScreenW(Context ctx) {
        int w = ;
        if (Build.VERSION.SDK_INT > ) {
            Point p = new Point();
            ((WindowManager) ctx.getSystemService(Context.WINDOW_SERVICE))
                    .getDefaultDisplay().getSize(p);
            w = p.x;
        } else {
            w = ((WindowManager) ctx.getSystemService(Context.WINDOW_SERVICE))
                    .getDefaultDisplay().getWidth();
        }
        return w;
    }

 /**
     * get the height of screen *
     */
    public static int getScreenH(Context ctx) {
        int h = ;
        if (Build.VERSION.SDK_INT > ) {
            Point p = new Point();
            ((WindowManager) ctx.getSystemService(Context.WINDOW_SERVICE))
                    .getDefaultDisplay().getSize(p);
            h = p.y;
        } else {
            h = ((WindowManager) ctx.getSystemService(Context.WINDOW_SERVICE))
                    .getDefaultDisplay().getHeight();
        }
        return h;
    }

 /**
     * 获得屏幕高度
     *
     * @param context
     * @return
     */
    public static int getScreenWidth(Context context) {
        WindowManager wm = (WindowManager) context
                .getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics outMetrics = new DisplayMetrics();
        wm.getDefaultDisplay().getMetrics(outMetrics);
        return outMetrics.widthPixels;
    }

相关源码：

ScreenUtil@[Github]