如何解决此错误目标主机不能为null，或者在此代码中的参数中设置

Question

  

我尝试在listview中从url下载图像，但是这段代码   给出错误＆＃34; 目标主机不能为空，或在参数中设置＆＃34;以及如何删除此错误

public Bitmap downloadBitmap(String url) {
    final AndroidHttpClient client = AndroidHttpClient.newInstance("Android");
    final HttpGet getRequest = new HttpGet(url);
    try {
        HttpResponse response = client.execute(getRequest);
        final int statusCode = response.getStatusLine().getStatusCode();
        if (statusCode != HttpStatus.SC_OK) {
            Log.w("ImageDownloader", "Error " + statusCode + " while retrieving bitmap from " + url);
            return null;
        }

        final HttpEntity entity = response.getEntity();
        if (entity != null) {
            InputStream inputStream = null;
            try {
                inputStream = entity.getContent();
                final Bitmap bitmap = BitmapFactory.decodeStream(inputStream);
                return bitmap;
            } finally {
                if (inputStream != null) {
                    inputStream.close();
                }
                entity.consumeContent();
            }
        }
    } catch (Exception e) {
        // Could provide a more explicit error message for IOException or IllegalStateException
        getRequest.abort();
        Log.w("ImageDownloader", "Error while retrieving bitmap from " + url);
    } finally {
        if (client != null) {
            client.close();
        }
    }
    return null;
}