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Implementation steps of vue crop preview component function

不言
不言Original
2018-05-05 11:02:141571browse

This article mainly introduces the implementation code of the vue cutting preview component function. This article introduces it to you in great detail through a combination of example codes. It has certain reference value. Interested friends can follow the script home small Let’s learn together

vue version cutting tool, including preview function

Final effect: qiuyaofan.github.io/vue-crop-de…

Source code address: github .com/qiuyaofan/v…

The first step: first use vue-cli to install the scaffolding (see the vue-cli official website if you don’t know how to install it)

// 初始化vue-cli
vue init webpack my-plugin

Step 2: Create files

Create new src/views/validSlideDemo.vue,

Create new VueCrop/index.js,VueCrop.vue in src/components,

Configure access routes in routes/index.js (see github source code for details)

The final generated file structure is as shown below:

The third step: Register components

1. Reference all plug-ins: src/components/index.js

// 导入插件入口文件
import VueCrop from './VueCrop/index.js'
const install = function (Vue, opts = {}) {
 /* 如果已安装就跳过 */
 if (install.installed) return
 // 注册插件
 Vue.component(VueCrop.name, VueCrop)
}
// 全局情况下注册插件
if (typeof window !== 'undefined' && window.Vue) {
 install(window.Vue)
}
export {
 install,
 // 此处是为了兼容在vue内单独引入这个插件,如果是main.js全局引入就可以去掉
 VueCrop
}

2. Call plug-ins globally: src/main. js (vue plugins official document explanation install)

import Vue from 'vue'
import App from './App'
import router from './router'
// 新加的:导入入口文件
import { install } from 'src/components/index.js'
// 全局调用,相当于调用 `MyPlugin.install(Vue)`
Vue.use(install)
Vue.config.productionTip = false
/* eslint-disable no-new */
new Vue({
 el: '#app',
 router,
 components: { App },
 template: &#39;<App/>&#39;
})

3.VueCrop entry file calls VueCrop.vue: src/components/VueCrop/index.js

// 导入vue
import VueCrop from &#39;./VueCrop.vue&#39;
// Vue.js 的插件应当有一个公开方法 install 。这个方法的第一个参数是 Vue 构造器
VueCrop.install = function (Vue) {
 // 注册组件
 Vue.component(VueCrop.name, VueCrop)
}
export default VueCrop

Summary: I always had a misunderstanding at the beginning, thinking that myPlugin.install is a method of vue. In fact, it is not. It is just a public method for us to construct plugin knowledge. The method that can be understood as the constructor in native js:

function MyPlugin(){
 console.info(&#39;构造函数&#39;)
}
MyPlugin.prototype.install=function(vue,options){
 console.info(&#39;构造器vue:&#39;+vue);
}

And what actually registers the component is: Vue.component()

So, the process of vue plug-in registration is:

1. Call main.js:

import { install } from &#39;src/components/index.js&#39;
vue.use(install)

2.index .js adds the install method and calls Vue.component to register the component

3. The index.js in the component is the same as the index.js of all components

Step 4: Design and develop your own components. Build the component structure

Before this, you can first understand the naming convention of the component, etc. You can refer to the article Nuggets: Vue front-end development specifications, of which point 2 is explained in detail

First, determine Your own calling method and parameters that need to be exposed

<vue-crop
:crop-url="cropUrl1"
:ratio="ratio"
:height="460"
:width="460"
:previewJson="previewJson1"
class="c-crop--preview_right"
@afterCrop="afterCrop"
>
>

Among them, @afterCrop="afterCrop" is the callback function after cropping is completed, and the others are attribute configurations

In the componentsrc/components/VueCrop/VueCrop.vue, you can use this.$emit('afterCrop') to trigger the afterCrop event in the demo

In terms of component structure, it is mainly divided into: main part of cropping, selection frame component (VueCropTool.vue), calculation of cropping frame width, position coordinates, etc. (VueCropMove.js), drag event registration public js (components/utils/ draggable.js)

draggable.js is based on the one in element, with some modifications. The source code is as follows

export default function (element, options) {
 const moveFn = function (event) {
  if (options.drag) {
   options.drag(event)
  }
 }
 // mousedown fn
 const downFn = function (event) {
  if (options.start) {
   // 调用参数中start函数
   options.start(event)
  }
 }
 // mouseup fn
 const upFn = function (event) {
  document.removeEventListener(&#39;mousemove&#39;, moveFn)
  document.removeEventListener(&#39;mouseup&#39;, upFn)
  document.onselectstart = null
  document.ondragstart = null
  if (options.end) {
   // 调用参数中end函数
   options.end(event)
  }
 }
 // 绑定事件
 element.addEventListener(&#39;mousedown&#39;, event => {
  if (options.stop && options.stop(event, element) === false) {
   return false
  }
  document.onselectstart = function () {
   return false
  }
  document.ondragstart = function () {
   return false
  }
  document.addEventListener(&#39;mousedown&#39;, downFn)
  document.addEventListener(&#39;mousemove&#39;, moveFn)
  document.addEventListener(&#39;mouseup&#39;, upFn)
 })
}

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