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背景：点击图标，生成海报后，点击保存相册，可以保存

生成海报：插件wxa-plugin-canvas，此处使用页面异步生成组件方式，官网地址：wxa-plugin-canvas - npm

二维码：调用后端接口生成二维码

1.二维码按钮

          <!-- 二维码按钮 --><view class="item" bindtap="onCreatePoster"><van-icon name="scan" size="20px" /><view class="icon-title">二维码</view></view>

2.二维码海报显示图层

<!-- 二维码海报：注意布局要和其他元素独立 -->
<view bindtap="closePoster"><!-- 一定要设置元素的id="poster" --><poster id="poster" config="{{posterConfig}}" bind:success="onPosterSuccess" bind:fail="onPosterFail"></poster><view wx:if="{{posterShow}}" class="popup-mask"></view><view wx:if="{{posterShow}}" class="posterImg-box"><image mode="widthFix" class="posterImg" src="{{posterImg}}"></image><view class="btn-create" data-pic="{{basicInfo.pic}}" catchtap="savePosterPic">保存到相册</view></view>
</view>

3.点击按钮后异步生成海报

需要调用获取图片信息接口wx.getImageInfo()，获取到图片的宽高以做整体宽高配置

  /*** 异步生成海报*/async onCreatePoster() {console.log("异步生成海报");// 获取二维码信息(实质是后端生成的一张二维码图片)const qrRes = await createQRCode({id: this.data.basicInfo.id});console.log(qrRes,"qrRes");// 获取图片信息,图片获取成功后调用方法生成海报const pic = this.data.basicInfo.pic;wx.getImageInfo({src: pic,success:(res)=> {console.log(res.width)// console.log(res.height)const height = 490 * res.height / res.width// setData配置数据，数据配置完成后，生成海报this.createPosterDone(height, qrRes.data);}})},createPosterDone(picHeight,qrCode){const _this = thisconst _baseHeight = 74 + (picHeight + 120)this.setData({posterConfig: {// 海报总宽高width: 750,height: picHeight + 660,backgroundColor: '#fff',debug: false,// 图片所在容器起始位置，宽高等配置blocks: [{x: 76,y: 74,width: 604,height: picHeight + 120,borderWidth: 2,borderColor: '#c2aa85',borderRadius: 8}],// 图片配置images: [{x: 133,y: 133,url: _this.data.goodsInfoList.basicInfo.pic, // 商品图片width: 490,height: picHeight},{x: 76,y: _baseHeight + 199,url: qrCode, // 二维码width: 222,height: 222}],// 文字信息：商品标题、价格、二维码处文字texts: [{x: 375,y: _baseHeight + 80,width: 650,lineNum: 2,text: _this.data.goodsInfoList.basicInfo.name,textAlign: 'center',fontSize: 40,color: '#333'},{x: 375,y: _baseHeight + 180,text: '￥' + _this.data.goodsInfoList.basicInfo.minPrice,textAlign: 'center',fontSize: 50,color: '#e64340'},{x: 352,y: _baseHeight + 320,text: '长按识别小程序码',fontSize: 28,color: '#999'}],}}, () => {Poster.create(this.data.posterConfig, this);});},

4.海报生成成功后将海报数据（海报临时路径）和是否显示海报层，存放到data中

data:{// 二维码海报配置posterConfig:{},// poster显示标识posterShow: false,// 保存到相册的图片posterImg: ''
},onPosterSuccess(e){console.log("二维码生成成功");this.setData({posterImg: e.detail,posterShow: true})},

5.点击海报任何位置，除了保存到相册按钮，隐藏海报层

closePoster方法绑定到最外层

保存按钮使用catchbind阻止冒泡，即可防止点击保存时也会关掉海报层

<!-- 二维码海报：注意布局要和其他元素独立 -->
<view bindtap="closePoster"><!-- 一定要设置元素的id="poster" --><poster id="poster" config="{{posterConfig}}" bind:success="onPosterSuccess" bind:fail="onPosterFail"></poster><view wx:if="{{posterShow}}" class="popup-mask"></view><view wx:if="{{posterShow}}" class="posterImg-box"><image mode="widthFix" class="posterImg" src="{{posterImg}}"></image><view class="btn-create" data-pic="{{basicInfo.pic}}" catchtap="savePosterPic">保存到相册</view></view>
</view>

  // 关闭海报closePoster(){this.setData({posterShow: false})},

6.点击保存到相册按钮，调用wx.saveImageToPhotosAlbum()方法保存图片到本地

注意wx.saveImageToPhotosAlbum()方法的参数filePath不能是绝对路径或者网络图片，必须是临时图片。所以在生成海报成功后需要将图片保存到data的posterImg中，保存时用这个就可以了

// 保存海报到相册savePosterPic(e){console.log("保存到相册",e);console.log(this.data.posterImg);//http://tmp/xlHB02MBJ50H9887bf9a40b5b5dc24b904e4132afcb0.pngwx.saveImageToPhotosAlbum({// 不能直接使用this.data.basicInfo.pic的图片// "saveImageToPhotosAlbum:fail https://file.winwebedu.com/mall/collage-01.jpg not absolute path"filePath: this.data.posterImg,success(res) { wx.showToast({title: '保存成功',})},fail(err){console.log(err);wx.showToast({title: '保存失败',})},// 无论成功与否关闭海报complete(){this.setData({posterShow: false});}})},

7.补充，如果要直接生成二维码不使用异步

<poster class="wxcode-box" id="poster" config="{{posterConfig}}" bind:success="onPosterSuccess" bind:fail="onPosterFail"></poster>

onPosterSuccess(e){// console.log("二维码生成成功");const { detail } = e;console.log(detail);wx.previewImage({current: detail,urls: [detail]})},posterConfig配置：jdConfig: {width: 750,height: 1334,backgroundColor: '#fff',debug: false,pixelRatio: 1,blocks: [{width: 690,height: 808,x: 30,y: 183,borderWidth: 2,borderColor: '#f0c2a0',borderRadius: 20,},{width: 634,height: 74,x: 59,y: 770,backgroundColor: '#fff',opacity: 0.5,zIndex: 100,},],texts: [{x: 113,y: 61,baseLine: 'middle',text: '伟仔',fontSize: 32,color: '#8d8d8d',},{x: 30,y: 113,baseLine: 'top',text: '发现一个好物，推荐给你呀',fontSize: 38,color: '#080808',},{x: 92,y: 810,fontSize: 38,baseLine: 'middle',text: '标题标题标题标题标题标题标题标题标题',width: 570,lineNum: 1,color: '#8d8d8d',zIndex: 200,},{x: 59,y: 895,baseLine: 'middle',text: [{text: '2人拼',fontSize: 28,color: '#ec1731',},{text: '¥99',fontSize: 36,color: '#ec1731',marginLeft: 30,}]},{x: 522,y: 895,baseLine: 'middle',text: '已拼2件',fontSize: 28,color: '#929292',},{x: 59,y: 945,baseLine: 'middle',text: [{text: '商家发货&售后',fontSize: 28,color: '#929292',},{text: '七天退货',fontSize: 28,color: '#929292',marginLeft: 50,},{text: '运费险',fontSize: 28,color: '#929292',marginLeft: 50,},]},{x: 360,y: 1065,baseLine: 'top',text: '长按识别小程序码',fontSize: 38,color: '#080808',},{x: 360,y: 1123,baseLine: 'top',text: '超值好货一起拼',fontSize: 28,color: '#929292',},],images: [{width: 62,height: 62,x: 30,y: 30,borderRadius: 62,url: 'https://img.yzcdn.cn/vant/cat.jpeg',},{width: 634,height: 634,x: 59,y: 210,url: 'https://b.yzcdn.cn/vant/icon-demo-1126.png',},{width: 220,height: 220,x: 92,y: 1020,url: 'https://img.yzcdn.cn/vant/cat.jpeg',},{width: 750,height: 90,x: 0,y: 1244,url: 'https://b.yzcdn.cn/vant/icon-demo-1126.png',}]},