vue-element-admin上传图片的功

在vue后台管理系统里面，有时候会遇到一个图片上传的功能，做这个功能的时候的思路是这样的：
1：首选由前端写一个图片上传的upload标签，选择本地的图片文件之后
2:调用后端给的接口，以二进制文件的形式传给后端服务器
3:服务器进行处理，处理完成之后将服务器的主机名加到图片名称的前缀上
4:返回一个有服务器主机+图片名称的在线就可以访问的链接给到前端
5:前端直接将在线链接路径渲染在界面显示图片

在vue-element-admin里面的具体的实践

1:在store/modules里面新建一个api.js
将上传图片至服务器的后端小伙伴给的接口写在这个js里面

const baseUrl = 'http://39.xx.xxx.1xx/yyexploreplatform'
const state = {
  fileUpload: baseUrl + '/upload/file'
}

export default { state }

2：打开store/getters.js
getters.js

const getters = {
  fileUpload: state => state.api.fileUpload,
}
export default getters

 3：新建一个index.vue页面

 开始写代码：

<template>
  <div class="app-container">
        <el-form ref="nextProjectForm" :model="nextProjectForm" label-width="100px">
          <el-form-item label="插入图片">
            <el-upload
              class="avatar-uploader"
              :action="fileUpload"
              :headers="{ Authorization: token }"
              :show-file-list="false"
              :on-success="handleAvatarSuccess">
         
              <img
                v-if="nextProjectForm.publicWelfareUrl"
                :src="nextProjectForm.publicWelfareUrl"
                class="avatar"/>
              <i v-else class="el-icon-plus avatar-uploader-icon"></i>
            </el-upload>
          </el-form-item>           
        </el-form>
  </div>
</template>
<script>
import { mapGetters } from "vuex";
export default {
  data() {
    return {
      nextProjectForm: {
        publicWelfareUrl: "",
      },
    };
  },
  computed: {
    ...mapGetters(["fileUpload", "token"])
  },
  methods: {
   
    handleAvatarSuccess(response, file, fileList) {
      if (response && response.data && response.data.url) {
        this.$set(this.nextProjectForm, "publicWelfareUrl", response.data.url);
      }
    },
   
  }
};
</script>
<style lang='scss'>
.avatar-uploader .el-upload {
  border: 1px dashed #d9d9d9;
  border-radius: 6px;
  cursor: pointer;
  position: relative;
  overflow: hidden;
}
.avatar-uploader .el-upload:hover {
  border-color: #409eff;
}
.avatar-uploader-icon {
  font-size: 28px;
  color: #8c939d;
   178px;
  height: 178px;
  line-height: 178px;
  text-align: center;
}
.avatar {
   178px;
  height: 178px;
  display: block;
}
</style>

4:效果如下：

5：有些业务需求是这样的，给定一个图片尺寸，比如说最大宽度是500，最大高度是300，如果上传的图片尺寸超过这个范围，在上传的时候，一个提示，不符合这个尺寸的都无法上传。
这个时候，就需要进行判断了

需要在upload里面添加一个:before-upload方法

 然后在 methods里面写一下这个方法的实现过程代码

 //对图片大小的限制
    handleImagesUrlBefore:function(file){
                var _this = this;
                return new Promise(function(resolve, reject) {
                    var reader = new FileReader();
                    reader.onload = function(event) {
                        var image = new Image();
                        image.onload = function () {
                            var width = this.width;
                            var height = this.height;
                            if (width>500 ){
                                _this.$alert('图片宽度尺寸必须在500之内！', '提示', {confirmButtonText: '确定'});
                                reject();
                            }
                            if (height >300) {
                                _this.$alert('图片高度尺寸必须在300之内！', '提示', {confirmButtonText: '确定'});
                                reject();
                            }
                            resolve();
                        };
                        image.src = event.target.result;
                    }
                    reader.readAsDataURL(file);
                });
            },

完整的参考代码：

<template>
  <div class="app-container">
        <el-form ref="nextProjectForm" :model="nextProjectForm" label-width="100px">
          <el-form-item label="插入图片">
            <el-upload
              class="avatar-uploader"
              :action="fileUpload"
              :before-upload="handleImagesUrlBefore"
              :headers="{ Authorization: token }"
              :show-file-list="false"
              :on-success="handleAvatarSuccess">
         
              <img
                v-if="nextProjectForm.publicWelfareUrl"
                :src="nextProjectForm.publicWelfareUrl"
                class="avatar"/>
              <i v-else class="el-icon-plus avatar-uploader-icon"></i>
            </el-upload>
          </el-form-item>           
        </el-form>
  </div>
</template>
<script>
import { mapGetters } from "vuex";
export default {
  data() {
    return {
      nextProjectForm: {
        publicWelfareUrl: "",
      },
    };
  },
  computed: {
    ...mapGetters(["fileUpload", "token"])
  },
  methods: {
    //对图片大小的限制
    handleImagesUrlBefore:function(file){
                var _this = this;
                return new Promise(function(resolve, reject) {
                    var reader = new FileReader();
                    reader.onload = function(event) {
                        var image = new Image();
                        image.onload = function () {
                            var width = this.width;
                            var height = this.height;
                            if (width>500 ){
                                _this.$alert('图片宽度尺寸必须在500之内！', '提示', {confirmButtonText: '确定'});
                                reject();
                            }
                            if (height >300) {
                                _this.$alert('图片高度尺寸必须在300之内！', '提示', {confirmButtonText: '确定'});
                                reject();
                            }
                            resolve();
                        };
                        image.src = event.target.result;
                    }
                    reader.readAsDataURL(file);
                });
            },

    handleAvatarSuccess(response, file, fileList) {
      if (response && response.data && response.data.url) {
        this.$set(this.nextProjectForm, "publicWelfareUrl", response.data.url);
      }
    },
   
  }
};
</script>
<style lang='scss'>
.avatar-uploader .el-upload {
  border: 1px dashed #d9d9d9;
  border-radius: 6px;
  cursor: pointer;
  position: relative;
  overflow: hidden;
}
.avatar-uploader .el-upload:hover {
  border-color: #409eff;
}
.avatar-uploader-icon {
  font-size: 28px;
  color: #8c939d;
   178px;
  height: 178px;
  line-height: 178px;
  text-align: center;
}
.avatar {
   178px;
  height: 178px;
  display: block;
}
</style>

如果不符合尺寸的时候，会有一个弹框进行提示

参考资源：

作者：祈澈菇凉
链接：https://www.jianshu.com/p/60e3208f23e0
来源：简书