Android - 如何从 s3 下载图像？

Question

我正在阅读 s3 android 指南，我真的很困惑如何下载我的文件。

他们提供了这段代码:

TransferObserver observer = transferUtility.download(
  MY_BUCKET,     /* The bucket to download from */
  OBJECT_KEY,    /* The key for the object to download */
  MY_FILE        /* The file to download the object to */
);

那么什么是 MY_FILE？我是否应该创建一个本地空文件对象并将其提供给 transferUtility 下载函数并将该空文件填充到一个下载？

并且，当我完成获取文件(特别是图像)时，我如何使用 glide 或 Picasso 将该文件上传到 imageView？

我不确定如何使用 TransferObserver 对象。

希望有人能提供一个工作示例，拜托!

干杯!

Answer 1

虽然我回答这个问题已经很晚了。希望这对陷入此问题的人有所帮助。

您不需要公开存储桶。您可以通过 Glide 直接显示图像。这是我通过 Glide 从 amazon s3 bucket 加载图像的 repo。

https://github.com/jontyankit/Glide-Amazon-Image-Load

您需要覆盖 GlideModule 并注册我们的组件

public class CustomGlideModule implements GlideModule {

@Override
public void applyOptions(Context context, GlideBuilder builder) {
    builder.setDecodeFormat(DecodeFormat.PREFER_ARGB_8888);
}

@Override
public void registerComponents(Context context, Glide glide) {
    glide.register(ImageModel.class, InputStream.class, new ImageLoader.Factory());
}
}

制作自定义 ModelLoader 类。该类根据上述模型而不是URL获取图片

 public class ImageLoader implements ModelLoader<ImageModel, InputStream> {

private final ModelCache<ImageModel, ImageModel> mModelCache;

public ImageLoader(ModelCache<ImageModel, ImageModel> mModelCache) {
    this.mModelCache = mModelCache;
}

@Override
public DataFetcher<InputStream> getResourceFetcher(ImageModel model, int width, int height) {
    ImageModel imageModel = model;
    if (mModelCache != null) {
        imageModel = mModelCache.get(model, 0, 0);
        if (imageModel == null) {
            mModelCache.put(model, 0, 0, model);
            imageModel = model;
        }
    }
    return new ImageFetcher(imageModel);
}

public static class Factory implements ModelLoaderFactory<ImageModel, InputStream> {

    private final ModelCache<ImageModel, ImageModel> mModelCache = new ModelCache<>(500);

    @Override
    public ModelLoader<ImageModel, InputStream> build(Context context, GenericLoaderFactory factories) {
        return new ImageLoader(mModelCache);
    }

    @Override
    public void teardown() {

    }
}

}

最后创建自定义类 DataFetcher。 public InputStream loadData(Priority priority) 是从亚马逊下载图片的方法。

public class ImageFetcher implements DataFetcher<InputStream> {

private final ImageModel imageModel;
private InputStream mInputStream;
boolean downloadComplete = false;
int transferId = 0;

public ImageFetcher(ImageModel imageModel) {
    this.imageModel = imageModel;
}

@Override
public InputStream loadData(Priority priority) throws Exception {
    return fetchStream(imageModel);
}

private InputStream fetchStream(final ImageModel imageModel) {
    TransferUtility transferUtility = AmazonClient.getClient().getTransferUtility();
    TransferObserver bolomessages = transferUtility.download(imageModel.getBucketName(), imageModel.getId(), new File(imageModel.getLocalPath()));
    transferId = bolomessages.getId();

    bolomessages.setTransferListener(new TransferListener() {

        @Override
        public void onStateChanged(int id, TransferState state) {
            Log.wtf("AWSS3", "onStateChanged = " + state);
            if (state == TransferState.COMPLETED) {
                File initialFile = new File(imageModel.getLocalPath());
                try {
                    mInputStream = new FileInputStream(initialFile);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                }
                downloadComplete = true;
            }
        }

        @Override
        public void onProgressChanged(int id, long bytesCurrent, long bytesTotal) {
        }

        @Override
        public void onError(int id, Exception ex) {
            // do something
            Log.wtf("AWSS3", "onError");
            ex.printStackTrace();
            downloadComplete = true;
        }
    });
    while (!downloadComplete){}
    return mInputStream;
}

@Override
public void cleanup() {
    if (mInputStream != null) {
        try {
            mInputStream.close();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            mInputStream = null;
        }
    }
}

@Override
public String getId() {
    return imageModel.getId();
}

@Override
public void cancel() {
    AmazonClient.getClient().getTransferUtility().cancel(transferId);
}
}