關於BitmapFactory.decodeStream(is)方法無法正常解碼爲Bitmap對象的解決方法

轉自：http://blog.csdn.net/andypan1314/article/details/6670320

在android sdk 1.6版本API幫助文檔中，其中關於BitmapFactory.decodeFactory.decodeStream(InputStream is)的幫助文檔是這麼說明的：

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.

注意黑體字。以下是具體代碼：

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;

}

後來調試發現，result爲null，加之查看幫助文檔中的黑體字，
所以在所獲得的InputStream不爲空的情況下，調用BitmapFactory.decodeStream(is)方法，他也有可能無法解碼成bitmap,剛開始我懷疑是本身圖片地址有問題，或圖片自身格式不正確，但通過瀏覽器查看，圖片顯示正常，而且，我是保存了幾十張圖片，但每次都會有個別幾張圖片無法正常顯示，需要重複下載三四次，纔可能保存成功。

後來在一篇文章中才發現，原來這是android 1.6版本的一個bug！

有牛人提出的一個解決辦法，我試了試，問題解決了

首先在原方法中改一句：

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

再創建一個類：

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;
        }

    }

第二種方法：最終用的是這種方法

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();
}

/*
     * 得到圖片字節流 數組大小
     * */
    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();
    }