JIM.getInstance().getMessageManager().setMessageUploadProvider(this);

// 开发者实现上传方法
@Override
public void uploadMessage(Message message, UploadCallback uploadCallback) {
    Handler mH = new Handler(Looper.getMainLooper());
    mH.postDelayed(new Runnable() {
        @Override
        public void run() {
            //模拟上传进度回调
            uploadCallback.onProgress(50);
        }
    }, 100);
    mH.postDelayed(new Runnable() {
        @Override
        public void run() {
            MediaMessageContent mediaMessageContent = (MediaMessageContent) message.getContent();
            String localPath = mediaMessageContent.getLocalPath();
            // 使用 localPath 获取文件内容并进行上传
            if (true) {
                //上传成功
                mediaMessageContent.setUrl("xxxxxx");//上传的文件 url
                uploadCallback.onSuccess(message);
            } else {
                uploadCallback.onError();
            }
        }
    }, 1000);
}