1.判断是否是ios设备

var ios = window.__wxjs_is_wkwebview;
if(ios){//判断是否是ios
       that.iosPreview(localIds);
}else {
       localIds.forEach(item => {
            that.imgList.push(item);
       })
}

2.采用异步请求的方式，在methods里面定义方法:

async iosPreview(localIds){
         for(var i = 0; i < localIds.length; i++) {
             await this.readImage(localIds[i]);
         }
},
readImage(item){
         let _this = this;
         return new Promise((resolve, reject) => {
               wx.getLocalImgData({
                      localId: item,
                      success: function(res) {
                          let localData = res.localData;
                          localData = localData.replace('jgp', 'jpeg');
                          _this.imgList.push(localData);
                          resolve('done!');
                      },
                      fail: function() {

                      }
               })   
         })     
}