安卓开发：用输入输出流实现往sdcard下载文件时，下载到途中程序闪退，这是为什么？

Question

用输入输出流实现往sdcard下载apk文件时，下载到途中程序闪退，有时候下载到28%，有时候到6%，每次不同，但都下载不成功程序就停止运行了。apk文件大小为10M，手机卡上的容量有300多M。代码如下：

public File getFileFromServer(String path, ProgressDialog pd) throws Exception{

        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            URL url = new URL(path);
            HttpURLConnection conn = (HttpURLConnection) url.openConnection();
            conn.setConnectTimeout(5000);

            pd.setMax(conn.getContentLength());
            InputStream is = conn.getInputStream();
            if (ActivityCompat.checkSelfPermission(getActivity(), Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED) {
                ActivityCompat.requestPermissions(getActivity(), new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},1);
            }
            File file = new File(Environment.getExternalStorageDirectory().getAbsolutePath(), "updata.apk");
            FileOutputStream fos = new FileOutputStream(file);
            BufferedInputStream bis = new BufferedInputStream(is);
            byte[] buffer = new byte[1024];
            int len ;
            int total=0;
            while((len =bis.read(buffer)) > 0){
                fos.write(buffer, 0, len);
                total+= len;
                //获取当前下载量
                pd.setProgress(total);
            }
            fos.flush();
            bis.close();
            is.close();
            return file;
        }
        else{
            return null;
        }
    }

Answer 1

抛异常还是内存溢出，有闪退的日志吗？另外，耗时操作放到其他线程里去