BitmapFactory.decodeStream(inputStream)返回null的解决方法

场景：Android，通过inputStream从网络上获取图片 

随后两次使用BitmapFactory对InputStream进行操作，一次获取宽高，另一次缩放

但是在缩放时，发现inputStream不能用了

原因是inputStream使用了之后，就不能再次使用了

The problem was that once you've used an InputStream from a HttpUrlConnection, you can't rewind and use the same InputStream again.

 

解决办法就是把inputStream里面的数据提取出来，针对数据进行操作就好了

tips:16384是每次迭代从InputStream里面读取的数据量的，是2的N次方，作者使用这个数字是出于效率考虑的

16384 is a fairly arbitrary choice although I tend to favour powers of 2 to increase the chance of the array aligning with word boundaries. pihentagy's answer shows how you can avoid using an intermediate buffer, but rather allocate an array of the correct size. Unless you're dealing with large files I personally prefer the code above, which is more elegant and can be used for InputStreams where the number of bytes to read is not known in advance

 public static byte[] streamToByte(InputStream is) {

        ByteArrayOutputStream buffer = new ByteArrayOutputStream();



        int nRead;

        byte[] data = new byte[16384];



        try {

            while ((nRead = is.read(data, 0, data.length)) != -1) {

                buffer.write(data, 0, nRead);

            }

            buffer.flush();

        } catch (IOException e) {

            e.printStackTrace();

            return null;

        }



        return buffer.toByteArray();

    }