Android截屏方案

Android截屏

Android截屏的原理：获取具体需要截屏的区域的Bitmap，然后绘制在画布上，保存为图片后进行分享或者其它用途

在截屏功能中，有时需要截取全屏的内容，有时需要截取超过一屏的内容（比如：Listview，Scrollview，RecyclerView）。下面介绍各种场景获取Bitmap的方法

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(), 0, 0, 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 >= 11) {
            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(0, MeasureSpec.UNSPECIFIED),
                    MeasureSpec.makeMeasureSpec(0, MeasureSpec.UNSPECIFIED));
            v.layout(0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());
        }
        Bitmap b = Bitmap.createBitmap(v.getDrawingCache(), 0, 0, v.getMeasuredWidth(), v.getMeasuredHeight());

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

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]。

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

public static Bitmap shotScrollView(ScrollView scrollView) {
  int h = 0;
  Bitmap bitmap = null;
  for (int i = 0; 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;
}

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。

public static Bitmap shotListView(ListView listview) {

  ListAdapter adapter = listview.getAdapter();
  int itemscount = adapter.getCount();
  int allitemsheight = 0;
  List<Bitmap> bmps = new ArrayList<Bitmap>();

  for (int i = 0; i < itemscount; i++) {

    View childView = adapter.getView(i, null, listview);
    childView.measure(
        View.MeasureSpec.makeMeasureSpec(listview.getWidth(), View.MeasureSpec.EXACTLY),
        View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED));

    childView.layout(0, 0, 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 = 0;

  for (int i = 0; i < bmps.size(); i++) {
    Bitmap bmp = bmps.get(i);
    bigcanvas.drawBitmap(bmp, 0, iHeight, paint);
    iHeight += bmp.getHeight();

    bmp.recycle();
    bmp = null;
  }

  return bigbitmap;
}

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。

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;
    LruCache<String, Bitmap> bitmaCache = 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) {

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

相信有不少小伙伴用BRVH第三方库来做recycleview的适配器的。使用这个库的话再用上面的方法会报角标越界的错误，看了BRVH的源码

public void onBindViewHolder(ViewHolder holder, int positions) {
       int viewType = holder.getItemViewType();
       switch(viewType) {
       case 0:
           this.convert((BaseViewHolder)holder, this.mData.get(holder.getLayoutPosition() - this.getHeaderLayoutCount()));
       case 273:
       case 819:
       case 1365:
           break;
       case 546:
           this.addLoadMore(holder);
           break;
       default:
           this.convert((BaseViewHolder)holder, this.mData.get(holder.getLayoutPosition() - this.getHeaderLayoutCount()));
           this.onBindDefViewHolder((BaseViewHolder)holder, this.mData.get(holder.getLayoutPosition() - this.getHeaderLayoutCount()));
       }

   }

在调用adapter.onBindViewHolder时，因为里面的position参数未使用，里面用的计算holder.getLayoutPosition() - this.getHeaderLayoutCount()的值一直是-1导致角标越界报错。

本人理解，RecyclerView的截屏原理是，首先构造每个item的ViewHolder，然后调用具体设置数据到每个item的方法，此时cache中就存有item的内容，此时绘制就能获取到完整的内容。采用v7包中的onBindViewHolder方法即可，或者是BRVH的convert方法，可以看到BRVH中没有暴露出这个方法，而且唯一暴露出的onBindViewHolder还会报角标越界错误，此时我们就需要在BRVH的基础上暴露出convert即可，代码如下

public class MyAdapter extends BaseQuickAdapter<T> {

       public MyAdapter() {
           super(getItemLayoutResId(), datas);
       }

       /**
        * 用于对外暴露convert方法,构造缓存视图(截屏用)
        * @param viewHolder
        * @param t
        */
       public void startConvert(BaseViewHolder viewHolder, T t){
           convert(viewHolder,t);
       }

       @Override
       protected void convert(BaseViewHolder viewHolder, T t) {
           bindView(viewHolder, t);
       }
   }

然后将上面所述的获取Bitmap方法修改一下

/**
    * 截取recycler view
    */
   public static Bitmap getRecyclerViewScreenshot(RecyclerView view) {
       BaseListFragment.MyAdapter adapter = (BaseListFragment.MyAdapter) view.getAdapter();
       Bitmap bigBitmap = null;
       if (adapter != null) {
           int size = adapter.getData().size();
           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;
           LruCache<String, Bitmap> bitmaCache = new LruCache<>(cacheSize);
           for (int i = 0; i < size; i++) {
               BaseViewHolder holder = (BaseViewHolder) adapter.createViewHolder(view, adapter.getItemViewType(i));
               //此处需要调用convert方法，否则绘制出来的都是空的item
               adapter.startConvert(holder, adapter.getData().get(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) {

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

合成Bitmap

比如四张合成一张

/**
   * 将四张图拼成一张
   *
   * @param pic1 图一
   * @param pic2 图二
   * @param pic3 图三
   * @param pic4 图四
   * @return only_bitmap
   * 详情见说明：{@link com.bertadata.qxb.util.ScreenShotUtils}
   */
  public static Bitmap combineBitmapsIntoOnlyOne(Bitmap pic1, Bitmap pic2, Bitmap pic3, Bitmap pic4, Activity context) {
      int w_total = pic2.getWidth();
      int h_total = pic1.getHeight() + pic2.getHeight() + pic3.getHeight() + pic4.getHeight();
      int h_pic1 = pic1.getHeight();
      int h_pic4 = pic4.getHeight();
      int h_pic12 = pic1.getHeight() + pic2.getHeight();
      //此处为防止OOM需要对高度做限制
      if (h_total > HEIGHTLIMIT) {
          return null;
      }

      Bitmap only_bitmap = Bitmap.createBitmap(w_total, h_total, Bitmap.Config.ARGB_4444);
      Canvas canvas = new Canvas(only_bitmap);
      canvas.drawColor(ContextCompat.getColor(context, R.color.color_content_bg));
      canvas.drawBitmap(pic1, 0, 0, null);
      canvas.drawBitmap(pic2, 0, h_pic1, null);
      canvas.drawBitmap(pic3, 0, h_pic12, null);
      canvas.drawBitmap(pic4, 0, h_total - h_pic4, null);
      return only_bitmap;
  }

图片后期处理

/**
    * 将传入的Bitmap合理压缩后输出到系统截屏目录下
    * 命名格式为：Screenshot+时间戳+启信宝报名.jpg
    * 同时通知系统重新扫描系统文件
    *
    * @param pic1    图一 标题栏截图
    * @param pic2    图二 scrollview截图
    * @param context 用于通知重新扫描文件系统，为提升性能可去掉
    *                详情见说明：{@link com.bertadata.qxb.util.ScreenShotUtils}
    */
   public static void savingBitmapIntoFile(final Bitmap pic1, final Bitmap pic2, final Activity context, final BitmapAndFileCallBack callBack) {
       if (context == null || context.isFinishing()) {
           return;
       }
       Thread thread = new Thread(new Runnable() {
           @Override
           public void run() {
               String fileReturnPath = "";
               int w = pic1.getWidth();
               Bitmap bottom = BitmapFactory.decodeResource(context.getResources(), R.drawable.ic_picture_combine_bottom);
               Bitmap top_banner = BitmapFactory.decodeResource(context.getResources(), R.drawable.ic_picture_combine_top);

               Bitmap bitmap_bottom = anyRatioCompressing(bottom, (float) w / bottom.getWidth(), (float) w / bottom.getWidth());
               Bitmap bitmap_top = anyRatioCompressing(top_banner, (float) w / bottom.getWidth(), (float) w / bottom.getWidth());
               final Bitmap only_bitmap = combineBitmapsIntoOnlyOne(bitmap_top, pic1, pic2, bitmap_bottom, context);

               // 获取当前时间
               SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss-ms", Locale.getDefault());
               String data = sdf.format(new Date());

               // 获取内存路径
               // 设置图片路径+命名规范
               // 声明输出文件
               String storagePath = Environment.getExternalStorageDirectory().getAbsolutePath();
               String fileTitle = "Screenshot_" + data + "_com.bertadata.qxb.biz_info.jpg";
               String filePath = storagePath + "/DCIM/";
               final String fileAbsolutePath = filePath + fileTitle;
               File file = new File(fileAbsolutePath);

               /**
                * 质压与比压结合
                * 分级压缩
                * 输出文件
                */
               if (only_bitmap != null) {
                   try {
                       // 首先，对原图进行一步质量压缩,形成初步文件
                       FileOutputStream fos = new FileOutputStream(file);
                       only_bitmap.compress(Bitmap.CompressFormat.JPEG, 50, fos);

                       // 另建一个文件other_file预备输出
                       String other_fileTitle = "Screenshot_" + data + "_com.bertadata.qxb.jpg";
                       String other_fileAbsolutePath = filePath + other_fileTitle;
                       File other_file = new File(other_fileAbsolutePath);
                       FileOutputStream other_fos = new FileOutputStream(other_file);

                       // 其次，要判断质压之后的文件大小，按文件大小分级进行处理
                       long file_size = file.length() / 1024; // size of file(KB)
                       if (file_size < 0 || !(file.exists())) {
                           // 零级： 文件判空
                           throw new NullPointerException();
                       } else if (file_size > 0 && file_size <= 256) {
                           // 一级： 直接输出
                           deleteFile(other_file);
                           // 通知刷新文件系统，显示最新截取的图文件
                           fileReturnPath = fileAbsolutePath;
                           context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + fileAbsolutePath)));
                       } else if (file_size > 256 && file_size <= 768) {
                           // 二级： 简单压缩:压缩为原比例的3/4，质压为50%
                           anyRatioCompressing(only_bitmap, (float) 3 / 4, (float) 3 / 4).compress(Bitmap.CompressFormat.JPEG, 40, other_fos);
                           deleteFile(file);
                           // 通知刷新文件系统，显示最新截取的图文件
                           fileReturnPath = other_fileAbsolutePath;
                           context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + other_fileAbsolutePath)));
                       } else if (file_size > 768 && file_size <= 1280) {
                           // 三级： 中度压缩：压缩为原比例的1/2，质压为40%
                           anyRatioCompressing(only_bitmap, (float) 1 / 2, (float) 1 / 2).compress(Bitmap.CompressFormat.JPEG, 40, other_fos);
                           deleteFile(file);
                           // 通知刷新文件系统，显示最新截取的图文件
                           fileReturnPath = other_fileAbsolutePath;
                           context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + other_fileAbsolutePath)));
                       } else if (file_size > 1280 && file_size <= 2048) {
                           // 四级： 大幅压缩：压缩为原比例的1/3，质压为40%
                           anyRatioCompressing(only_bitmap, (float) 1 / 3, (float) 1 / 3).compress(Bitmap.CompressFormat.JPEG, 40, other_fos);
                           deleteFile(file);
                           // 通知刷新文件系统，显示最新截取的图文件
                           fileReturnPath = other_fileAbsolutePath;
                           context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + other_fileAbsolutePath)));
                       } else if (file_size > 2048) {
                           // 五级： 中度压缩：压缩为原比例的1/2，质压为40%
                           anyRatioCompressing(only_bitmap, (float) 1 / 2, (float) 1 / 2).compress(Bitmap.CompressFormat.JPEG, 40, other_fos);
                           deleteFile(file);
                           // 通知刷新文件系统，显示最新截取的图文件
                           fileReturnPath = other_fileAbsolutePath;
                           context.sendBroadcast(new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE, Uri.parse("file://" + other_fileAbsolutePath)));
                       }

                       // 注销fos;
                       fos.flush();
                       other_fos.flush();
                       other_fos.close();
                       fos.close();
                       //callback用于回传保存成功的路径以及Bitmap
                       callBack.onSuccess(only_bitmap, fileReturnPath);
                   } catch (Exception e) {
                       e.printStackTrace();
                   }
               } else callBack.onSuccess(null, "");
           }
       });
       thread.start();
   }

/**
 * 可实现任意宽高比例压缩（宽高压比可不同）的压缩方法（主要用于微压）
 *
 * @param bitmap       源图
 * @param width_ratio  宽压比（float）（0<&&<1)
 * @param height_ratio 高压比（float）（0<&&<1)
 * @return 目标图片
 * <p>
 */
public static Bitmap anyRatioCompressing(Bitmap bitmap, float width_ratio, float height_ratio) {
    Matrix matrix = new Matrix();
    matrix.postScale(width_ratio, height_ratio);
    return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(), bitmap.getHeight(), matrix, false);
}

本文参考http://www.cnblogs.com/BoBoMEe/p/4556917.html，并结合自己实际项目操作完成