Facebook 照片的 Android 多部分/表单数据编码

Question

用于将照片上传到 Facebook 相册的新 Facebook Android SDK 是这样工作的 link :

Bundle params = new Bundle();
params.putString("source", "{image-data}");
/* make the API call */
new Request(
session,
"/me/photos",
params,
HttpMethod.POST,
new Request.Callback() {
    public void onCompleted(Response response) {
        /* handle the result */
    }
 }
).executeAsync();

让我困惑的是{image-data}，它说照片应该被编码为multipart/form-data，但是来自params。 putString("source", "{image-data}") 我们可以看到putString()的第二个参数应该是一个String，怎么才能我对图像文件 multipart/form-data 进行编码并以 String 格式获取返回值？像这样:

public String getImageFormData(File image){
   String imageValue;
    ...

    return imageValue;
}

还是我理解错了，我现在的问题是我有图片文件，如何使用上面的代码成功上传图片到Facebook？

Answer 1

文档中的示例代码似乎有误。似乎您所需要的只是一个名为“source”的(多部分)参数，其中包含已编码的图像数据。

下面是来自 Facebook Android SDK 的代码，用于将 Bundle 值转换为请求参数:

public void writeObject(String key, Object value) throws IOException {
    if (isSupportedParameterType(value)) {
        writeString(key, parameterToString(value));
    } else if (value instanceof Bitmap) {
        writeBitmap(key, (Bitmap) value);
    } else if (value instanceof byte[]) {
        writeBytes(key, (byte[]) value);
    } else if (value instanceof ParcelFileDescriptor) {
        writeFile(key, (ParcelFileDescriptor) value, null);
    } else if (value instanceof ParcelFileDescriptorWithMimeType) {
        writeFile(key, (ParcelFileDescriptorWithMimeType) value);
    } else {
        throw new IllegalArgumentException("value is not a supported type: String, Bitmap, byte[]");
    }
}

public void writeBitmap(String key, Bitmap bitmap) throws IOException {
    writeContentDisposition(key, key, "image/png");
    // Note: quality parameter is ignored for PNG
    bitmap.compress(Bitmap.CompressFormat.PNG, 100, outputStream);
    writeLine("");
    writeRecordBoundary();
    logger.appendKeyValue("    " + key, "<Image>");
}

特别是，对于 Bundle 中的任何位图，它们会为其序列化并创建适当的多部分 header 。您可以尝试将图像作为位图添加到 Bundle 中。您的 getImageFormData 方法可能类似于:

public Bitmap getImageFormData(File image) {
    return BitmapFactory.decodeFile(image.getPath());
}

您也可以尝试提供一个 ParcelFileDescriptor，它以类似的方式序列化:

public ParcelFileDescriptor getImageFormData(File image) {
    try {
        return ParcelFileDescriptor.open(image, ParcelFileDescriptor.MODE_READ_ONLY);
    } catch (FileNotFoundException e) {
        return null;
    }
}

此方法可能也很有趣(允许您使用 url 参数而不是源):

/**
 * Creates a new Request configured to upload an image to create a staging resource. Staging resources
 * allow you to post binary data such as images, in preparation for a post of an Open Graph object or action
 * which references the image. The URI returned when uploading a staging resource may be passed as the image
 * property for an Open Graph object or action.
 *
 * @param session
 *            the Session to use, or null; if non-null, the session must be in an opened state
 * @param image
 *            the image to upload
 * @param callback
 *            a callback that will be called when the request is completed to handle success or error conditions
 * @return a Request that is ready to execute
 */
public static Request newUploadStagingResourceWithImageRequest(Session session,
        Bitmap image, Callback callback) {
    Bundle parameters = new Bundle(1);
    parameters.putParcelable(STAGING_PARAM, image);

    return new Request(session, MY_STAGING_RESOURCES, parameters, HttpMethod.POST, callback);
}