vue-resource使用progress没有变化的过程，直接返回100%

Question

相关代码块儿如下：

this.$http.post('/api/XXX', this.XXX, {
    progress: progressEvent => {
        if (progressEvent.lengthComputable) {
            this.$nextTick(() => {
                // this.percent = Math.ceil((progressEvent.loaded / progressEvent.total) * 100);
                console.log(Math.ceil((progressEvent.loaded / progressEvent.total) * 100));
            })
        }
    }
}).then(({ data: { code, data, message } }) => {

只能打印出100，没有progress的变化过程，请问该怎么改？