真机效果

开发者工具效果

想要的效果是弹窗底部和屏幕底部紧贴着

// 头像、昵称弹窗
    show_modal: function (params) {
        var that = this;
        var show_modal = that.data.show_modal;
        var result = that.data.result;

        var animation = wx.createAnimation({
            duration: 500,
            timingFunction: 'ease'
        });

        if (show_modal == true) {
            show_modal = false;
            animation.translateY('0%').step()
        } else {
            show_modal = true;
            animation.translateY('-120%').step()
        }

        that.setData({
            show_modal,
            nickname: result['nickname'],
            ani: animation.export()
        })
    },

谢谢大佬