[移动开发]小程序wx.onLocationChange向下兼容wx.getLocation

由于wx.getLocation新版有了频率限制，好好的定位接口不能再频繁调用。只能用新版的wx.onLocationChange，但是新版的wx.onLocationChange必须在2.8.1以上才能使用。最后没办法只能做向下兼容
首先判断当前微信的版本号，这里我用了当初判断ios机型的api来获取版本号，存储在全局里面

let capsuleObj = wx.getMenuButtonBoundingClientRect();
wx.getSystemInfo({
      success: (res) => {
           if(res.platform == "ios" || res.system.indexOf('iOS') > -1 || res.system.indexOf('macOS') > -1){
             this.globalData.isIos = true;
           }
           // console.log("==获取系统信息==");
           var statusBarHeight = res.statusBarHeight; //顶部状态栏高度
           this.globalData.headerHeight = statusBarHeight + capsuleObj.height + (capsuleObj.top - statusBarHeight) * 2;
           let version = res.SDKVersion; // 获取当前基础库版本号
           this.globalData.version = version.replace(/\./g, ""); //去除点转换为数字来比较大小 
       },
       fail() {
       }
   })

然后在获取定位的页面

 // 定时获取当前经纬度
    getlocation() {
        wx.getLocation({
            type: 'gcj02',
            success: res => {
                this.data.signInfo.signLongitude = res.longitude;
                this.data.signInfo.signLatitude = res.latitude;
            },
            fail: error => {
                wx.showModal({
                    title: '提示',
                    content: '定位失败，请检查是否授权定位',
                    showCancel: false,
                    success:res=> {
                        this.toSetting();
                    }
                })
            }
        })
        if (this.data.localTimer) {
            clearInterval(this.data.localTimer)
            this.data.localTimer = null;
        }
        if(app.globalData.version > 2160){
            // 如果当前微信版本库大于2.17.0调取新接口
            this.data.localTimer = setInterval(() => {
                this.getWxLocation() //等待
            }, 3000)
        }else {
        	// 低版本调取老接口
            this.data.localTimer = setInterval(() => {
                wx.getLocation({
                    type: 'gcj02',
                    success: res => {
                        this.data.signInfo.signLongitude = res.longitude;
                        this.data.signInfo.signLatitude = res.latitude;
                      
                    },
                    fail: error => {
                    }
                })
            }, 3000)
        }
    },
    // 新版获取定位
    getWxLocation() {
        let that = this;
        try {
            let _locationChangeFn = (res) => {
                that.data.signInfo.signLongitude = res.longitude;
                that.data.signInfo.signLatitude = res.latitude;
                wx.offLocationChange(_locationChangeFn) //只监听一次后关闭 
            }
            // 开启小程序进入前台时接收位置消息
            wx.startLocationUpdate({
                success: (res) => {
                	// 监听位置信息
                    wx.onLocationChange(_locationChangeFn)
                },
                fail: (err) => {}
            })
        } catch (error) {

        }
    },
    //设置去开启定位权限
    toSetting() {
        let self = this
        wx.openSetting({
            success(res) {
                if (res.authSetting["scope.userLocation"]) {
                    // res.authSetting["scope.userLocation"]为trueb表示用户已同意获得定位信息，此时调用getlocation可以拿到信息
                }
            }
        })
    },
    

最后别忘了在销毁页面时关闭定时器

  onUnload: function () {
        if (this.data.localTimer) {
            clearInterval(this.data.localTimer);
            this.data.localTimer = null;
        }
    },