Android截屏總結

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Android截屏的原理：獲取具體需要截屏的區域的Bitmap，然後繪制在畫布上，保存為圖片後進行分享或者其它用途。

在截屏功能中，有時需要截取全屏的內容，有時需要截取超過一屏的內容（比如：Listview，Scrollview，RecyclerView）。下面介紹各種場景獲取Bitmap的方法

普通截屏的做到

獲取當前Window的DrawingCache的方式，即decorView的DrawingCache

/***shotthecurrentscreen,withthestatusbutthestatusistrans**@paramctxcurrentactivity*/publicstaticBitmapshotActivity(Activityctx){Viewview=ctx.getWindow().getDecorView();view.setDrawingCacheEnabled(true);view.buildDrawingCache();Bitmapbp=Bitmap.createBitmap(view.getDrawingCache(),0,0,view.getMeasuredWidth(),view.getMeasuredHeight());view.setDrawingCacheEnabled(false);view.destroyDrawingCache();returnbp;}

獲取當前View的DrawingCache

publicstaticBitmapgetViewBp(Viewv){if(null==v){returnnull;}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());}Bitmapb=Bitmap.createBitmap(v.getDrawingCache(),0,0,v.getMeasuredWidth(),v.getMeasuredHeight());v.setDrawingCacheEnabled(false);v.destroyDrawingCache();returnb;}

開源方案

在滾動視圖中，如果當前View並沒有在視圖中全部繪制出來，我們可以利用View的ScrollTo()和ScrollBy()方法來移動畫布，同時獲取當前View的可視部分的DrawingCache，最後進行拼接得到其Bitmap，參考

https://github.com/PGSSoft/scrollscreenshot

Scrollview截屏

三個截屏中，ScrollView最簡單，因為ScrollView只有一個childView，雖然沒有全部顯示在界面上，但是已經全部渲染繪制，因此可以直接調用scrollView.draw(canvas)來完成截圖

publicstaticBitmapshotScrollView(ScrollViewscrollView){inth=0;Bitmapbitmap=null;for(inti=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);finalCanvascanvas=newCanvas(bitmap);scrollView.draw(canvas);returnbitmap;}

listview截屏

而ListView就是會回收與重用Item，並且只會繪制在螢幕上顯示的ItemView，根據stackoverflow上大神的建議，採用一個List來存儲Item的視圖，這種方案依然不夠好，當Item足夠多的時候，可能會發生oom。

publicstaticBitmapshotListView(ListViewlistview){ListAdapteradapter=listview.getAdapter();intitemscount=adapter.getCount();intallitemsheight=0;List<Bitmap>bmps=newArrayList<Bitmap>();for(inti=0;i<itemscount;i++){ViewchildView=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();}Bitmapbigbitmap=Bitmap.createBitmap(listview.getMeasuredWidth(),allitemsheight,Bitmap.Config.ARGB_8888);Canvasbigcanvas=newCanvas(bigbitmap);Paintpaint=newPaint();intiHeight=0;for(inti=0;i<bmps.size();i++){Bitmapbmp=bmps.get(i);bigcanvas.drawBitmap(bmp,0,iHeight,paint);iHeight+=bmp.getHeight();bmp.recycle();bmp=null;}returnbigbitmap;}

RecyclerView截屏

我們都知道，在新的Android版本中，已經可以用RecyclerView來代替使用ListView的場景，相比較ListView，RecyclerView對Item View的緩存支持的更好。可以採用和ListView相同的方案，這里也是在stackoverflow上看到的方案。

publicstaticBitmapshotRecyclerView(RecyclerViewview){RecyclerView.Adapteradapter=view.getAdapter();BitmapbigBitmap=null;if(adapter!=null){intsize=adapter.getItemCount();intheight=0;Paintpaint=newPaint();intiHeight=0;finalintmaxMemory=(int)(Runtime.getRuntime().maxMemory()/1024);//Use1/8thoftheavailablememoryforthismemorycache.finalintcacheSize=maxMemory/8;LruCache<String,Bitmap>bitmaCache=newLruCache<>(cacheSize);for(inti=0;i<size;i++){RecyclerView.ViewHolderholder=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();BitmapdrawingCache=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);CanvasbigCanvas=newCanvas(bigBitmap);DrawablelBackground=view.getBackground();if(lBackgroundinstanceofColorDrawable){ColorDrawablelColorDrawable=(ColorDrawable)lBackground;intlColor=lColorDrawable.getColor();bigCanvas.drawColor(lColor);}for(inti=0;i<size;i++){Bitmapbitmap=bitmaCache.get(String.valueOf(i));bigCanvas.drawBitmap(bitmap,0f,iHeight,paint);iHeight+=bitmap.getHeight();bitmap.recycle();}}returnbigBitmap;}

相信有不少小夥伴用BRVH第三方庫來做recycleview的適配器的。使用這個庫的話再用上面的方法會報角標越界的錯誤，看了BRVH的源碼

publicvoidonBindViewHolder(ViewHolderholder,intpositions){intviewType=holder.getItemViewType();switch(viewType){case0:this.convert((BaseViewHolder)holder,this.mData.get(holder.getLayoutPosition()-this.getHeaderLayoutCount()));case273:case819:case1365:break;case546: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()));}}

在調用adapter.onBindViewHolder時，因為里面的position參數未使用，里面用的計算holder.getLayoutPosition() – this.getHeaderLayoutCount()的值一直是-1導致角標越界報錯。

本人理解，RecyclerView的截屏原理是，首先構造每個item的ViewHolder，然後調用具體設置數據到每個item的方法，此時cache中就存有item的內容，此時繪制就能獲取到完整的內容。採用v7包中的onBindViewHolder方法即可，

或者是BRVH的convert方法，可以看到BRVH中沒有暴露出這個方法，而且唯一暴露出的onBindViewHolder還會報角標越界錯誤，此時我們就需要在BRVH的基礎上暴露出convert即可，代碼如下

publicclassMyAdapterextendsBaseQuickAdapter<T>{publicMyAdapter(){super(getItemLayoutResId(),datas);}/***用於對外暴露convert方法,構造緩存視圖(截屏用)*@paramviewHolder*@paramt*/publicvoidstartConvert(BaseViewHolderviewHolder,Tt){convert(viewHolder,t);}@Overrideprotectedvoidconvert(BaseViewHolderviewHolder,Tt){bindView(viewHolder,t);}}

然後將上面所述的獲取Bitmap方法修改一下

/***截取recyclerview*/publicstaticBitmapgetRecyclerViewScreenshot(RecyclerViewview){BaseListFragment.MyAdapteradapter=(BaseListFragment.MyAdapter)view.getAdapter();BitmapbigBitmap=null;if(adapter!=null){intsize=adapter.getData().size();intheight=0;Paintpaint=newPaint();intiHeight=0;finalintmaxMemory=(int)(Runtime.getRuntime().maxMemory()/1024);//Use1/8thoftheavailablememoryforthismemorycache.finalintcacheSize=maxMemory/8;LruCache<String,Bitmap>bitmaCache=newLruCache<>(cacheSize);for(inti=0;i<size;i++){BaseViewHolderholder=(BaseViewHolder)adapter.createViewHolder(view,adapter.getItemViewType(i));//此處需要調用convert方法，否則繪制出來的都是空的itemadapter.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();BitmapdrawingCache=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);CanvasbigCanvas=newCanvas(bigBitmap);DrawablelBackground=view.getBackground();if(lBackgroundinstanceofColorDrawable){ColorDrawablelColorDrawable=(ColorDrawable)lBackground;intlColor=lColorDrawable.getColor();bigCanvas.drawColor(lColor);}for(inti=0;i<size;i++){Bitmapbitmap=bitmaCache.get(String.valueOf(i));bigCanvas.drawBitmap(bitmap,0f,iHeight,paint);iHeight+=bitmap.getHeight();bitmap.recycle();}}returnbigBitmap;}

合成Bitmap

比如四張合成一張

/***將四張圖拼成一張**@parampic1圖一*@parampic2圖二*@parampic3圖三*@parampic4圖四*@returnonly_bitmap*詳情見說明：{@linkcom.bertadata.qxb.util.ScreenShotUtils}*/publicstaticBitmapcombineBitmapsIntoOnlyOne(Bitmappic1,Bitmappic2,Bitmappic3,Bitmappic4,Activitycontext){intw_total=pic2.getWidth();inth_total=pic1.getHeight()+pic2.getHeight()+pic3.getHeight()+pic4.getHeight();inth_pic1=pic1.getHeight();inth_pic4=pic4.getHeight();inth_pic12=pic1.getHeight()+pic2.getHeight();//此處為防止OOM需要對高度做限制if(h_total>HEIGHTLIMIT){returnnull;}Bitmaponly_bitmap=Bitmap.createBitmap(w_total,h_total,Bitmap.Config.ARGB_4444);Canvascanvas=newCanvas(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);returnonly_bitmap;}

圖片後期處理

/***將傳入的Bitmap合理壓縮後輸出到系統截屏目錄下*命名格式為：Screenshot+時間戳+啟信寶報名.jpg*同時通知系統重新掃描系統文件*@parampic1圖一標題欄截圖*@parampic2圖二scrollview截圖*@paramcontext用於通知重新掃描文件系統，為提升性能可去掉*詳情見說明：{@linkcom.bertadata.qxb.util.ScreenShotUtils}*/publicstaticvoidsavingBitmapIntoFile(finalBitmappic1,finalBitmappic2,finalActivitycontext,finalBitmapAndFileCallBackcallBack){if(context==null||context.isFinishing()){return;}Threadthread=newThread(newRunnable(){@Overridepublicvoidrun(){StringfileReturnPath="";intw=pic1.getWidth();Bitmapbottom=BitmapFactory.decodeResource(context.getResources(),R.drawable.ic_picture_combine_bottom);Bitmaptop_banner=BitmapFactory.decodeResource(context.getResources(),R.drawable.ic_picture_combine_top);Bitmapbitmap_bottom=anyRatioCompressing(bottom,(float)w/bottom.getWidth(),(float)w/bottom.getWidth());Bitmapbitmap_top=anyRatioCompressing(top_banner,(float)w/bottom.getWidth(),(float)w/bottom.getWidth());finalBitmaponly_bitmap=combineBitmapsIntoOnlyOne(bitmap_top,pic1,pic2,bitmap_bottom,context);//獲取當前時間SimpleDateFormatsdf=newSimpleDateFormat("yyyy-MM-dd-HH-mm-ss-ms",Locale.getDefault());Stringdata=sdf.format(newDate());//獲取記憶體路徑//設置圖片路徑+命名規範//聲明輸出文件StringstoragePath=Environment.getExternalStorageDirectory().getAbsolutePath();StringfileTitle="Screenshot_"+data+"_com.bertadata.qxb.biz_info.jpg";StringfilePath=storagePath+"/DCIM/";finalStringfileAbsolutePath=filePath+fileTitle;Filefile=newFile(fileAbsolutePath);/***質壓與比壓結合*分級壓縮*輸出文件*/if(only_bitmap!=null){try{//首先，對原圖進行一步質量壓縮,形成初步文件FileOutputStreamfos=newFileOutputStream(file);only_bitmap.compress(Bitmap.CompressFormat.JPEG,50,fos);//另建一個文件other_file預備輸出Stringother_fileTitle="Screenshot_"+data+"_com.bertadata.qxb.jpg";Stringother_fileAbsolutePath=filePath+other_fileTitle;Fileother_file=newFile(other_fileAbsolutePath);FileOutputStreamother_fos=newFileOutputStream(other_file);//其次，要判斷質壓之後的文件大小，按文件大小分級進行處理longfile_size=file.length()/1024;//sizeoffile(KB)if(file_size<0||!(file.exists())){//零級：文件判空thrownewNullPointerException();}elseif(file_size>0&&file_size<=256){//一級：直接輸出deleteFile(other_file);//通知刷新文件系統，顯示最新截取的圖文件fileReturnPath=fileAbsolutePath;context.sendBroadcast(newIntent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,Uri.parse("file://"+fileAbsolutePath)));}elseif(file_size>256&&file_size<=768){//二級：簡單壓縮:壓縮為原比例的3/4，質壓為50%anyRatioCompressing(only_bitmap,(float)3/4,(float)3/4).compress(Bitmap.CompressFormat.JPEG,40,other_fos);deleteFile(file);//通知刷新文件系統，顯示最新截取的圖文件fileReturnPath=other_fileAbsolutePath;context.sendBroadcast(newIntent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,Uri.parse("file://"+other_fileAbsolutePath)));}elseif(file_size>768&&file_size<=1280){//三級：中度壓縮：壓縮為原比例的1/2，質壓為40%anyRatioCompressing(only_bitmap,(float)1/2,(float)1/2).compress(Bitmap.CompressFormat.JPEG,40,other_fos);deleteFile(file);//通知刷新文件系統，顯示最新截取的圖文件fileReturnPath=other_fileAbsolutePath;context.sendBroadcast(newIntent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,Uri.parse("file://"+other_fileAbsolutePath)));}elseif(file_size>1280&&file_size<=2048){//四級：大幅壓縮：壓縮為原比例的1/3，質壓為40%anyRatioCompressing(only_bitmap,(float)1/3,(float)1/3).compress(Bitmap.CompressFormat.JPEG,40,other_fos);deleteFile(file);//通知刷新文件系統，顯示最新截取的圖文件fileReturnPath=other_fileAbsolutePath;context.sendBroadcast(newIntent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,Uri.parse("file://"+other_fileAbsolutePath)));}elseif(file_size>2048){//五級：中度壓縮：壓縮為原比例的1/2，質壓為40%anyRatioCompressing(only_bitmap,(float)1/2,(float)1/2).compress(Bitmap.CompressFormat.JPEG,40,other_fos);deleteFile(file);//通知刷新文件系統，顯示最新截取的圖文件fileReturnPath=other_fileAbsolutePath;context.sendBroadcast(newIntent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE,Uri.parse("file://"+other_fileAbsolutePath)));}//註銷fos;fos.flush();other_fos.flush();other_fos.close();fos.close();//callback用於回傳保存成功的路徑以及BitmapcallBack.onSuccess(only_bitmap,fileReturnPath);}catch(Exceptione){e.printStackTrace();}}elsecallBack.onSuccess(null,"");}});thread.start();}/***可做到任意寬高比例壓縮（寬高壓比可不同）的壓縮方法（主要用於微壓）**@parambitmap源圖*@paramwidth_ratio寬壓比（float）（0<&&<1)*@paramheight_ratio高壓比（float）（0<&&<1)*@return目標圖片*<p>*/publicstaticBitmapanyRatioCompressing(Bitmapbitmap,floatwidth_ratio,floatheight_ratio){Matrixmatrix=newMatrix();matrix.postScale(width_ratio,height_ratio);returnBitmap.createBitmap(bitmap,0,0,bitmap.getWidth(),bitmap.getHeight(),matrix,false);}

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