一、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:

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() {

                      }
             })     
         })     
}

二、安卓设备:

if(ios){//判断是否是ios
    that.iosPreview(localIds);
}else {
    that.androidPreview(localIds);                          
}
//方法
async androidPreview(localIds){
      for(var i = 0; i < localIds.length; i++) {
          await this.getImage(localIds[i]);
      }   
},
getImage(item){
     let _this = this;
     _this.imgList.push(item);
     return new Promise((resolve, reject) => {
            wx.getLocalImgData({
                localId: item,
                success: function(res) {
                    let localData = res.localData;
                    var imgBase64=localData.substring(localData.indexOf(",") + 1);
                    _this.phoneArr +=imgBase64+ ",";
                    resolve('done!');
                    _this.uploadImg(item);                        
                },
                fail: function() {

                }                    
          	})         
      })             
}