android 从url下载文件并保存到内存盘

我尝试从 url 下载文件并将其保存到内存购物车，但我无法理解我的错误是什么，我的代码是

URL url = new URL(imageURL);
        File file = new File(fileName);

        long startTime = System.currentTimeMillis();
        Log.d("ImageManager", "download begining");
        Log.d("ImageManager", "download url:" + url);
        Log.d("ImageManager", "downloaded file name:" + fileName);
        URLConnection ucon = url.openConnection();
        InputStream is = ucon.getInputStream();
        BufferedInputStream bis = new BufferedInputStream(is);

        ByteArrayBuffer baf = new ByteArrayBuffer(50);
        int current = 0;
        while ((current = bis.read()) != -1) {
           baf.append((byte) current);
        }

        /* Convert the Bytes read to a String. */
        FileOutputStream fos = new FileOutputStream(file);
        fos.write(baf.toByteArray());
        fos.close();
        Log.d("ImageManager", "download ready in"
                        + ((System.currentTimeMillis() - startTime) / 1000)
                        + " sec");

但我在控制台中发现以下错误

12-27 14:50:01.302: D/EXCEPTION GET:(8062): java.io.FileNotFoundException: /my.jpg (Read-only file system)

其实我不知道我能做什么，请大家帮忙。

问题在于您保存文件的路径，文件名不应以/并将此修改应用到您的代码中。

File extStore = Environment.getExternalStorageDirectory();
File file = new File(extStore, fileName);

你应该检查媒体可用性 http://developer.android.com/guide/topics/data/data-storage.htmC#filesExternal在尝试保存之前。