添加前后屏交互指令常量js文件；添加支付结果页的指令监听&发送；

app.json

 {
   "pages": [
-    "pages/landscan/landscan",
     "pages/payresult/payresult",
+    "pages/landscan/landscan",
     "pages/index/index"
   ],
   "window": {

const/actioncmd.js

+//发送打印结果
+export const ACTION_PRINT_RESULT = "ACTION_PRINT_RESULT";
+
+//发送重打印指令
+export const ACTION_REPRINT = "ACTION_REPRINT";
\ No newline at end of file

pages/payresult/payresult.axml

@@ -37,7 +37,7 @@
             </block>
             <block a:else>
               <view hidden="{{isPrinting}}">
-                <button type="ghost" style="height:40rpx;margin:0 auto;border-radius:20rpx;border-color:#FF7F19;color:#FF7F19;width:166rpx;" hover-class="loginButtonHover" onTap="">重新打印</button>
+                <button type="ghost" style="height:40rpx;margin:0 auto;border-radius:20rpx;border-color:#FF7F19;color:#FF7F19;width:166rpx;" hover-class="loginButtonHover" onTap="onReprint">重新打印</button>
               </view>
             </block>
           </view>

pages/payresult/payresult.js

+import { ACTION_PRINT_RESULT } from '../../const/actioncmd'
+import { ACTION_REPRINT } from '../../const/actioncmd'
+
 Page({
   data: {
-    payFailedReason:"xxxxxxxxxxx",
-    isPaySuccess:true,
-    payPriceYuan:"--.--",
-    printResult:"正在打印小票...",
-    isPrinting:false,
-    isPrintSuccess:true,
-  },
-  onLoad() {},
+    payFailedReason: "xxxxxxxxxxx",
+    isPaySuccess: true,
+    payPriceYuan: "--.--",
+    printResult: "正在打印小票...",
+    isPrinting: false,
+    isPrintSuccess: true,
+  },
+  onLoad() { },
+
+  onShow() {
+    //开启后屏监听
+    my.ix.onBuddyMessage({
+      success: (res) => {
+        console.info(`onBuddyMessage success: ${JSON.stringify(res)}`);
+        if (res.action == ACTION_PRINT_RESULT) {
+          //获取到打印结果
+          var printResult = res.data;
+        } else {
+          //未知指令
+        }
+      }
+    });
+  },
+
+  onReprint() {
+    //通知前屏重新打印
+    my.ix.sendBuddyMessage({
+      // 填入目标小程序的 AppID
+      target: "****************",
+      data: {
+        action: ACTION_REPRINT,
+        data: null
+      },
+      success: (res) => {
+        console.info(`sendBuddyMessage success: ${JSON.stringify(res)}`);
+      },
+      fail: (res) => {
+        console.info(`sendBuddyMessage failed: ${JSON.stringify(res)}`);
+      }
+    });
+  },
+
+  onHide() {
+    //关闭后屏监听
+    my.ix.offBuddyMessage();
+  }
 });