如何检测整个图像已在Android中下载

Question

I download images into my android application with this code:

private void download(URL url, File file) throws IOException {
    Log.d(TAG, "download(): downloading file: " + url);

    URLConnection urlConnection = url.openConnection();
    InputStream inputStream = urlConnection.getInputStream();
    BufferedInputStream bufferStream;
    OutputStream outputStream = null;
    try {
        bufferStream = new BufferedInputStream(inputStream, 512);
        outputStream = new FileOutputStream(file);
        byte[] buffer = new byte[512];
        int current;
        while ((current = bufferStream.read(buffer)) != -1) {
            outputStream.write(buffer, 0, current);
        }
    } finally {
        if (outputStream != null) {
            outputStream.close();
        }
        if (inputStream != null) {
            inputStream.close();
        }
    }
}

This code works fine, but some users and testers complained about incomplete photos. I suspect small network lags which interrupt connection. So I would like to detect if whole image was downloaded and saved file is complete image. Is there any way how to detect file size from BufferedInputStream or is there another way how detect download completion?

Answer 1

I suggest using Google Volley which provides a super simple interface for networking in general, and image loading specifically. It takes care of threading and batching for you.

It's what Google use on the Google Play app.

It will solve your problem by providing listeners that notify you when the job is complete.

Answer 2

Try something like this . I think it could help you.

Answer 3

If you are downloading an ordinary file over HTTP, the method getContentLength() of URLConnection gives you the length that the file should have in the end.

You can compare the returned value of this method to the file length/length of downloaded data. If it's equal, then the file is complete:

int contentLength = urlConnection.getContentLength();
if (contentLength != -1) {
    if (contentLength == file.length()) {
        System.out.println("file is complete");
    } else {
        System.out.println("file is incomplete");
    }
} else {
    System.out.println("unknown if file is complete");
}