Android截屏总结

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);    }