关于使用HttpURLConnection下载大文件的一些问题 求大神指导

下面是我的函数
private void getFile() {
new Thread(new Runnable() {
@Override
public void run() {
synchronized (this) {
URL url = null;
InputStream inputStream = null;
FileOutputStream outputStream = null;
long fileSize = 0;
try {
url = new URL(downloadUrl);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setConnectTimeout(28000);
connection.setRequestMethod("GET");
if (connection.getResponseCode() == 200) {
inputStream = connection.getInputStream();
File file = new File(Environment.getExternalStorageDirectory() + "/" + directoriy, filename);
outputStream = new FileOutputStream(file);
fileSize = connection.getContentLength();
int length = 0;
byte[] buffer = new byte[1024];
int downloadSize = 0;
while ((length = inputStream.read(buffer)) != -1) {
downloadSize = downloadSize + length;
progress[0] = downloadSize / (float) fileSize;

                            outputStream.write(buffer, 0, length);
                            handler.sendEmptyMessage(INVALIDATE1);
                        }
                        outputStream.flush();
                        outputStream.close();
                        handler.sendEmptyMessage(LOAD_SUCCESS1);
                    }
                } catch (MalformedURLException e) {
                    handler.sendEmptyMessage(LOAD_ERROR1);
                    e.printStackTrace();
                    e.getMessage();
                    try {
                        if (inputStream != null)
                            inputStream.close();
                        if (outputStream != null)
                            outputStream.close();
                    } catch (IOException e1) {
                        e1.printStackTrace();
                    }
                } catch (IOException e) {
                    handler.sendEmptyMessage(LOAD_ERROR1);
                    e.printStackTrace();
                    if (inputStream != null)
                        try {
                            inputStream.close();
                        } catch (IOException e1) {
                            e1.printStackTrace();
                        }
                    if (outputStream != null)
                        try {
                            outputStream.close();
                        } catch (IOException e1) {
                            e1.printStackTrace();
                        }
                }
            }
        }
    }).start();

}

用上面的函数下载一个1个G的文件要改成POST方式吗？需要的话函数需要拿些改动呢，还有就是下载启动大文件之后对UI有很大的影响，列表直接卡住了，想请问用什么方法可以优化一下呢？

下载是耗时操作，肯定要开启一条新的线程来做这件事啊