java - 转换为 base64 并在结果中重复？

Question

我在 android 中获取 url 并使用此代码将数据流转换为 64 位数据字符串:

URL url = new URL("http://iranassistance.com/images/sos-logo.png");
HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setRequestMethod("GET");
//urlConnection.setDoOutput(true);
urlConnection.connect();
File SDCardRoot = Environment.getExternalStorageDirectory().getAbsoluteFile();
String filename="downloadedFile.png";
Log.i("Local filename:",""+filename);
File file = new File(SDCardRoot,filename);
if(file.createNewFile()) {
  file.createNewFile();
}
FileOutputStream fileOutput = new FileOutputStream(file);
InputStream inputStream = urlConnection.getInputStream();byte[] imageBytes = new byte[urlConnection.getContentLength()];
inputStream.read(imageBytes, 0, imageBytes.length);
inputStream.close();
String base64Image = Base64.encodeToString(imageBytes, Base64.DEFAULT);

但是 base64Image 结果不完整，给出了这样的东西:

......nUTJaJnb7PLyscfBMQLLiexyKSEh/o2RfctcZtc8Hr5xcAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA........

重复的“A”显示有问题，图像不完整!为什么这不能正常工作？

Answer 1

简单:

inputStream.read(imageBytes, 0, imageBytes.length);

您假设上述总是一次性读取所有字节。

错了。此方法读取它想要读取的字节数。因此它返回给您读取的数 字节。查看其 javadoc :

Returns: the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached.

换句话说:你必须循环并累积这些数字，直到你得到你正在寻找的字节数!

然后您得到了那些 A 字符:您的数组最初全为 0。如前所述:您只填充了该数组的部分。所以数组的其余部分仍然是 0 - 编码后结果为 AAAAA。