有人可以告诉我这段代码哪里出错了吗？基本上我希望应用程序下载一个 .png 文件，将其显示给用户并将其保存到 sd 卡以供将来参考。直到部分似乎一切都很好while ((len = webstream.read(buffer)) > 0)；因为调试器没有到达我放在这里的断点，而且我有一个空的 .png 文件目录。我有WRITE_EXTERNAL_STORAGE在我的清单中声明的许可。
protected class DownloadTask extends AsyncTask<String, Integer, Bitmap> {
@Override
protected Bitmap doInBackground(String... string) {
Bitmap d = null;
try {
DefaultHttpClient dhc = new DefaultHttpClient();
HttpGet request = new HttpGet(HTTP_BASE + string[0] + ".png");
HttpResponse response = dhc.execute(request);
BufferedInputStream webstream = new BufferedInputStream(response.getEntity().getContent());
d = BitmapFactory.decodeStream(webstream);
writeToSd(string[0], webstream, d);
}
catch (Exception ex) { ex.printStackTrace(); }
return d;
}
private void writeToSd(String string, BufferedInputStream webstream, Bitmap d) {
try {
webstream.mark(3);
webstream.reset();
File f = new File(Environment.getExternalStorageDirectory() + SD_DIR);
f.mkdirs();
File f2 = new File(f, string + ".png");
f2.createNewFile();
BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(f2));
int len;
byte[] buffer = new byte[1024];
while ((len = webstream.read(buffer)) > 0) {
fos.write(buffer, 0, len);
}
webstream.close();
//fos.flush();
fos.close();
}
catch (Exception ex) {
ex.printStackTrace();
}
}
protected void onPostExecute(Bitmap result) {
if (result != null) {
iv.setImageBitmap(result);
vs.setDisplayedChild(1);
}
}
};