从 App Engine 向 Android 应用发送图像数据

Question

在我的 App Engine 后端，我有一个从 Google Cloud Storage 获取图像的方法

@ApiMethod(
        name = "getProfileImage",
        path = "image",
        httpMethod = ApiMethod.HttpMethod.GET)
public Image getProfileImage(@Named("imageName")String imageName){
    try{
        HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
        GoogleCredential credential = GoogleCredential.getApplicationDefault();

        Storage.Builder storageBuilder = new Storage.Builder(httpTransport,new JacksonFactory(),credential);
        Storage storage = storageBuilder.build();

        Storage.Objects.Get getObject = storage.objects().get("mybucket", imageName);

        ByteArrayOutputStream out = new ByteArrayOutputStream();
        // If you're not in AppEngine, download the whole thing in one request, if possible.
        getObject.getMediaHttpDownloader().setDirectDownloadEnabled(false);
        getObject.executeMediaAndDownloadTo(out);

        byte[] oldImageData = out.toByteArray();
        out.close();

        ImagesService imagesService = ImagesServiceFactory.getImagesService();

        return ImagesServiceFactory.makeImage(oldImageData);
    }catch(Exception e){
        logger.info("Error getting image named "+imageName);
    }
    return null;
}

我遇到的问题是当我在我的 android 应用程序中调用它时如何获取图像数据？

由于您无法从应用引擎返回原语，我将其转换为 Image，以便我可以在我的应用中调用 getImageData() 来获取字节[]。

但是返回给应用的Image对象与应用引擎中的不同，所以没有getImageData()。

如何将图像数据获取到我的 Android 应用程序？

如果我创建了一个包含 byte[] 变量的对象，那么我使用字符串数据设置 byte[] 变量并从方法中返回该对象，这样行吗？

更新

图片是从安卓应用发送的。 （这段代码可能正确也可能不正确，我还没有调试过）

@WorkerThread
    public String startResumableSession(){
        try{
            File file = new File(mFilePath);
            long fileSize = file.length();
            file = null;
            String sUrl = "https://www.googleapis.com/upload/storage/v1/b/lsimages/o?uploadType=resumable&name="+mImgName;
            URL url = new URL(sUrl);
            HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
            urlConnection.setRequestProperty("Authorization","");
            urlConnection.setRequestProperty("X-Upload-Content-Type","image/png");
            urlConnection.setRequestProperty("X-Upload-Content-Length",String.valueOf(fileSize));
            urlConnection.setRequestMethod("POST");

            if(urlConnection.getResponseCode() == HttpURLConnection.HTTP_OK){
                return urlConnection.getHeaderField("Location");
            }
        }catch(Exception e){
            e.printStackTrace();
        }
        return null;
    }

    private long sendNextChunk(String sUrl,File file,long skip){
        int bytesRead, bytesAvailable, bufferSize;
        byte[] buffer;
        int maxBufferSize = 524287;
        long totalBytesSent = 0;
        try{
            long fileSize = file.length();
            FileInputStream fileInputStream = new FileInputStream(file);
            skip = fileInputStream.skip(skip);

            bytesAvailable = fileInputStream.available();
            bufferSize = Math.min(bytesAvailable, maxBufferSize);
            totalBytesSent = skip + bufferSize;
            buffer = new byte[bufferSize];

            bytesRead = fileInputStream.read(buffer, 0, bufferSize);
            try {
                while (bytesRead > 0) {

                    try {
                        URL url = new URL(sUrl);
                        HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
                        urlConnection.setDoInput(true);
                        urlConnection.setDoOutput(true);
                        urlConnection.setUseCaches(false);
                        urlConnection.setChunkedStreamingMode(524287);
                        urlConnection.setRequestMethod("POST");
                        urlConnection.setRequestProperty("Connection", "Keep-Alive");
                        urlConnection.setRequestProperty("Content-Type","image/png");
                        urlConnection.setRequestProperty("Content-Length",String.valueOf(bytesRead));
                        urlConnection.setRequestProperty("Content-Range", "bytes "+String.valueOf(skip)+"-"+String.valueOf(totalBytesSent)+"/"+String.valueOf(fileSize));

                        DataOutputStream outputStream = new DataOutputStream(urlConnection.getOutputStream());
                        outputStream.write(buffer, 0, bufferSize);

                        int code = urlConnection.getResponseCode();

                        if(code == 308){
                            String range = urlConnection.getHeaderField("Range");
                            return Integer.parseInt(range.split("-")[1]);
                        }else if(code == HttpURLConnection.HTTP_CREATED){
                            return -1;
                        }

                        outputStream.flush();
                        outputStream.close();
                        outputStream = null;
                    } catch (OutOfMemoryError e) {
                        e.printStackTrace();
//                        response = "outofmemoryerror";
//                        return response;
                        return -1;
                    }
                    fileInputStream.close();
                }
            } catch (Exception e) {
                e.printStackTrace();
//                response = "error";
//                return response;
                return -1;
            }
        }catch(Exception e){
            e.printStackTrace();
        }
        return -1;
    }

编辑 2：

显然人们不清楚我在我的 android 应用程序中使用 Endpoints

Answer 1

我最终做了什么/发现您需要在带有端点的 api 调用上调用 execute()，它会返回从 API 传回的真实数据

例子

api调用返回Image

public Image getProfileImage(@Named("id") long id, @Named("imageName")String imageName){
        try{
            ProfileRecord pr = get(id);
            HttpTransport httpTransport = GoogleNetHttpTransport.newTrustedTransport();
            GoogleCredential credential = GoogleCredential.getApplicationDefault();

            Storage.Builder storageBuilder = new Storage.Builder(httpTransport,new JacksonFactory(),credential);
            Storage storage = storageBuilder.build();

            Storage.Objects.Get getObject = storage.objects().get("mybucket", imageName);

        ByteArrayOutputStream out = new ByteArrayOutputStream();
        // If you're not in AppEngine, download the whole thing in one request, if possible.
        getObject.getMediaHttpDownloader().setDirectDownloadEnabled(false);
        getObject.executeMediaAndDownloadTo(out);

        byte[] oldImageData = out.toByteArray();
        out.close();
        return ImagesServiceFactory.makeImage(oldImageData);
    }catch(Exception e){
        logger.info("Error getting image named "+imageName);
    }
    return null;
}

然后在客户端我会这样调用它来获取它

Image i = pr.profileImage(id,"name.jpg").execute();
byte[] data = i.decodeImageData();

Answer 2

您可以为此使用 Google Cloud Endpoints：

Google Cloud Endpoints 由工具、库和功能组成 允许您从应用程序生成 API 和客户端库 引擎应用程序，称为 API 后端，用于简化客户端 从其他应用程序访问数据。端点更容易 为 Web 客户端和移动客户端创建 Web 后端，例如 Android 或 Apple 的 iOS。

见https://cloud.google.com/appengine/docs/java/endpoints/