JAVA高级面试进阶训练营视频教程

admin

在android sdk 1.6版本API帮助文档中，其中关于BitmapFactory.decodeFactory.decodeStream(InputStream is)的帮助文档是这么说明的：

 
Bitmap android.graphics.BitmapFactory.decodeStream(InputStream is)

public static Bitmap decodeStream (InputStream is) 
Since: API Level 1 
Decode an input stream into a bitmap. <strong>If the input stream is null, or cannot be used to decode a bitmap, the function returns null</strong>. The stream's position will be where ever it was after the encoded data was read.

Parameters
is  The input stream that holds the raw data to be decoded into a bitmap. 

Returns
The decoded bitmap, or null if the image data could not be decoded. 

public static Bitmap bmpFromURL(URL imageURL){
    Bitmap result = null;
    try {
        HttpURLConnection connection = (HttpURLConnection)imageURL .openConnection();
        connection.setDoInput(true);
        connection.connect();
        InputStream input = connection.getInputStream();
        result = BitmapFactory.decodeStream(input);
    } catch (IOException e) {
        e.printStackTrace();
    }
    return result;
}

后来调试发现，result为null，加之查看帮助文档中的黑体字，
所以在所获得的InputStream不为空的情况下，调用BitmapFactory.decodeStream(is)方法，他也有可能无法解码成bitmap,刚开始我怀疑是本身图片地址有问题，或图片自身格式不正确，但通过浏览器查看，图片显示正常，而且，我是保存了几十张图片，但每次都会有个别几张图片无法正常显示，需要重复下载三四次，才可能保存成功。

 

后来在一篇文章中才发现，原来这是android 1.6版本的一个bug！

 

有牛人提出的一个解决办法，我试了试，问题解决了

首先在原方法中改一句：

result = BitmapFactory.decodeStream(new PatchInputStream(input));

再创建一个类：

public class PatchInputStream extends FilterInputStream{

        protected PatchInputStream(InputStream in) {
            super(in);
            // TODO Auto-generated constructor stub
        }
        
        public long skip(long n)throws IOException{
            long m=0l;
            while(m<n){
                long _m=in.skip(n-m);
                if(_m==0l){
                    break;
                }
                m+=_m;
            }
            return m;
        }
    }

第二种方法：最终用的是这种方法

InputStream is = httpConn.getInputStream();

  if (is == null){
       throw new RuntimeException("stream is null");
  }else{
       try {
           byte[] data=readStream(is);
           if(data!=null){
           bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
       }
  } catch (Exception e) {
       e.printStackTrace();
  }
   is.close();
  }

    /*
     * 得到图片字节流 数组大小
     * */
    public static byte[] readStream(InputStream inStream) throws Exception{      
        ByteArrayOutputStream outStream = new ByteArrayOutputStream();      
        byte[] buffer = new byte[1024];      
        int len = 0;      
        while( (len=inStream.read(buffer)) != -1){      
            outStream.write(buffer, 0, len);      
        }      
        outStream.close();      
        inStream.close();      
        return outStream.toByteArray();      
    }