5

我不明白为什么会收到此 IO 异常。它在文档中说，"Throws IOException if the image format is not supported or can not be decoded."我"he stream's position will be where ever it was after the encoded data was read. Currently only the JPEG and PNG formats are supported."给它一个PNG，我什至通过使用输出图像类型bitmapOptions.outMimeType;，它说image/png

代码 ：

    @Override
protected List<String> doInBackground(String... urlo) {
    List<String> savedKeys = new ArrayList<String>();
    InputStream inputStream = null;
    try {
        URL url = new URL("https://upload.wikimedia.org/wikipedia/commons/thumb/4/47/PNG_transparency_demonstration_1.png/280px-PNG_transparency_demonstration_1.png");
           HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setDoInput(true);
            connection.connect();
           inputStream = connection.getInputStream();
    } catch (MalformedURLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }   



    BitmapFactory.Options bitmapOptions = new BitmapFactory.Options();
    bitmapOptions.inJustDecodeBounds = true;
    BitmapFactory.decodeStream(inputStream, null, bitmapOptions);
    int width = bitmapOptions.outWidth;
    int height = bitmapOptions.outHeight;
    String imageType = bitmapOptions.outMimeType;
    Debug.out(imageType);



    int block = 256;
    int count =0;
    BitmapRegionDecoder decoder = null;
    try {
        decoder = BitmapRegionDecoder.
            newInstance(inputStream, false);
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    Rect tileBounds = new Rect();
    // loop blocks
    for (int i=0; i<height; i+=block) {
        // get vertical bounds limited by image height
        tileBounds.top = i;
        int h = i+block<height ? block : height-i;
        tileBounds.bottom = i+h;
        tileBounds.right = 0;
        tileBounds.left = width;
        Debug.out(tileBounds.left+" "+tileBounds.right+" "+tileBounds.top+tileBounds.bottom);
            // load tile
        tile = decoder.decodeRegion(tileBounds, bitmapOptions);
        MainActivity.cache.put(key+count, tile);
          publishProgress();
          tile.recycle();
        savedKeys.add(key+count);

    }
    try {
        inputStream.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return savedKeys;

}
4

1 回答 1

2

异常不是因为错误的文件类型而被抛出，而是因为它不可读。

BitmapFactory.decodeStream(inputStream, null, bitmapOptions);

这会“遍历”流，并且您的流对象不再从头开始。

解决方案是在此之后再次调用inputStream = connection.getInputStream();，以将流返回到其原始可读状态。

于 2013-12-09T09:09:50.947 回答