设置恰当的inSampleSize能够使BitmapFactory分配更少的空间以消除该错误。inSampleSize的具体含义请参考SDK文档。例如:java
BitmapFactory.Options opts = new BitmapFactory.Options(); opts.inSampleSize = 4; Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);
设置恰当的inSampleSize是解决该问题的关键之一。BitmapFactory.Options提供了另外一个成员inJustDecodeBounds。算法
BitmapFactory.Options opts = new BitmapFactory.Options(); opts.inJustDecodeBounds = true; Bitmap bitmap = BitmapFactory.decodeFile(imageFile, opts);
设置inJustDecodeBounds为true后,decodeFile并不分配空间,但可计算出原始图片的长度和宽度,即opts.width和opts.height。有了这两个参数,再经过必定的算法,便可获得一个恰当的inSampleSize。数组
查看Android源码,Android提供了一种动态计算的方法。网络
public static int computeSampleSize(BitmapFactory.Options options, int minSideLength, int maxNumOfPixels) { int initialSize = computeInitialSampleSize(options, minSideLength, maxNumOfPixels); int roundedSize; if (initialSize <= 8) { roundedSize = 1; while (roundedSize < initialSize) { roundedSize <<= 1; } } else { roundedSize = (initialSize + 7) / 8 * 8; } return roundedSize; } private static int computeInitialSampleSize(BitmapFactory.Options options, int minSideLength, int maxNumOfPixels) { double w = options.outWidth; double h = options.outHeight; int lowerBound = (maxNumOfPixels == -1) ? 1 : (int) Math.ceil(Math.sqrt(w * h / maxNumOfPixels)); int upperBound = (minSideLength == -1) ? 128 : (int) Math.min(Math.floor(w / minSideLength), Math.floor(h / minSideLength)); if (upperBound < lowerBound) { // return the larger one when there is no overlapping zone. return lowerBound; } if ((maxNumOfPixels == -1) && (minSideLength == -1)) { return 1; } else if (minSideLength == -1) { return lowerBound; } else { return upperBound; } }
使用该算法,就可动态计算出图片的inSampleSize。app
BitmapFactory.Options opts = new BitmapFactory.Options(); opts.inJustDecodeBounds = true; BitmapFactory.decodeFile(imageFile, opts); opts.inSampleSize = computeSampleSize(opts, -1, 128*128); opts.inJustDecodeBounds = false; try { Bitmap bmp = BitmapFactory.decodeFile(imageFile, opts); imageView.setImageBitmap(bmp); } catch (OutOfMemoryError err) { }
另外,能够经过Bitmap.recycle()方法来释放位图所占的空间,固然前提是位图没有被使用。ide
获取缩略图关键代码:url
byte[] imageByte=getImageFromURL(urlPath[i].trim());
//如下是把图片转化为缩略图再加载 BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; //首先设置.inJustDecodeBounds为true Bitmap bitmap=BitmapFactory.decodeByteArray(imageByte, 0, imageByte.length, options); //这时获取到的bitmap是null的,还没有调用系统内存资源 options.inJustDecodeBounds = false; 获得图片有宽和高的options对象后,设置.inJustDecodeBounds为false。 int be = (int)(options.outHeight / (float)200); if (be <= 0) be = 1; options.inSampleSize = be; //计算获得图片缩小倍数 bitmaps[i]=BitmapFactory.decodeByteArray(imageByte, 0, imageByte.length,options); //获取真正的图片对象(缩略图) /** * 根据图片网络地址获取图片的byte[]类型数据 * @param urlPath 图片网络地址 * @return 图片数据 */ public byte[] getImageFromURL(String urlPath){ byte[] data=null; InputStream is=null; HttpURLConnection conn=null; try { URL url=new URL(urlPath); conn=(HttpURLConnection) url.openConnection(); conn.setDoInput(true); //conn.setDoOutput(true); conn.setRequestMethod("GET" ); conn.setConnectTimeout(6000 ); is=conn.getInputStream(); if(conn.getResponseCode()==200 ){ data=readInputStream(is); } else System.out.println("发生异常!" ); } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } finally{ conn.disconnect(); try { is.close(); } catch (IOException e) { e.printStackTrace(); } } return data; }
/** * 读取InputStream数据,转为byte[]数据类型 * @param is InputStream数据 * @return 返回byte[]数据 */ public byte[] readInputStream(InputStream is) { ByteArrayOutputStream baos=new ByteArrayOutputStream(); byte[] buffer=new byte[1024 ]; int length=-1 ; try { while((length=is.read(buffer))!=-1 ){ baos.write(buffer, 0 , length); } baos.flush(); } catch (IOException e) { e.printStackTrace(); } byte[] data=baos.toByteArray(); try { is.close(); baos.close(); } catch (IOException e) { e.printStackTrace(); } return data; } /** * 根据网络图片地址集批量获取网络图片 * @param urlPath 网络图片地址数组 * @return 返回Bitmap数据类型的数组 */ public Bitmap[] getBitmapArray(String[] urlPath){ int length=urlPath.length; if(urlPath==null||length<1 ){ return null; } else{ Bitmap[] bitmaps=new Bitmap[length]; for (int i = 0 ; i < length; i++) { byte[] imageByte=getImageFromURL(urlPath[i].trim()); //如下是把图片转化为缩略图再加载 BitmapFactory.Options options = new BitmapFactory.Options(); options.inJustDecodeBounds = true; Bitmap bitmap=BitmapFactory.decodeByteArray(imageByte, 0 , imageByte.length, options); options.inJustDecodeBounds = false; int be = (int)(options.outHeight / (float)200 ); if (be <= 0 ) be = 1 ; options.inSampleSize = be; bitmaps[i]=BitmapFactory.decodeByteArray(imageByte, 0 , imageByte.length,options); } return bitmaps; } }