【快应用】快应用学习之页面周期函数onBackPress无法触发？

【关键词】

onBackPress、退出提示

【问题背景】

在学习和调试快应用的过程中，我在子页面中的onBackPress()函数中定制了退出的一个弹框提醒，将它作为组件引入父页面中，弹框却无法触发？
问题代码如下：
子页面

<template>
<!-- Only one root node is allowed in template. -->
<div class="container ">
<div class="mlr-container">
<input onclick="hasinstallShortcut" type="button" value="Check Shortcut Creation" class="btn-blue" />
</div>
<div class="mlr-container">
<input onclick="deeplink" type="button" value="Create Shortcut By Deeplink" class="btn-blue" />
</div>
<div class="mlr-container">
<input onclick="setShortcut" type="button" value="Create Shortcut" class="btn-blue" />
</div>
<div class="mlr-container">
<shortcut-button class="shortcut" add-type="5" onclick="click()"></shortcut-button>
</div>
<div class="mlr-container">
<input onclick="turnTo" type="button" value="Turn To My QuickApp" class="btn-blue" />
</div>
</div>
</template>

<style lang="sass">
        .container {
        flex-direction: column;
        justify-content: center;
        align-items: center;
        }
        .mlr-container {
        margin-top: 50px;
        margin-right: 30px;
        margin-left: 30px;
        flex-direction: column;
        }
        .btn-blue {
        background-color: #0faeff;
        color: #ffffff;
        width:600px;
        height: 150px;
        font-size: 50px;
        border-radius:15px;
        }
        .shortcut {
        margin-top: 40px;
        background-color: #0faeff;
        color: rgb(22, 203, 219);
        font-size: 40px;
        width: 500px;
        height: 100px;
        border-radius: 220px;
        align-self: center;
        text-align: center;
        opacity: 0.4;
        }
</style>

<script>
  import shortcut from '@system.shortcut';
          import prompt from '@system.prompt';
          import router from '@system.router'
module.exports = {
        onInit: function () {
        this.$page.setTitleBar({
        text: '创建桌面图标',
        backgroundColor: '#007DFF',
        backgroundOpacity: 0.5,
        });
        },
        setShortcut() {
        shortcut.install({
        message: 'Adds the shortcut to the desktop for convenient use next time.',
        success: function (ret) {
        console.log('handling createShortCut success');
        },
        fail: function (erromsg, errocode) {
        prompt.showToast({
        message: erromsg+errocode,
        duration: 2000,
        gravity: 'bottom'
        })
        }
        });
        },
        hasinstallShortcut() {
        shortcut.hasInstalled({
        success: function (ret) {
        console.log('hasInstalled success ret---' + ret);
        if (ret) {
        // 桌面图标已创建   
        prompt.showToast({
        message: 'has',
        })
        } else {
        // 桌面图标未创建
        prompt.showToast({
        message: 'has not',
        })
        }
        }.bind(this),
        fail: function (erromsg, errocode) {
        console.log('hasInstalled fail ret---' + erromsg);
        }.bind(this),
        complete: function () {
        }
        });
        },
        deeplink() {
        router.push({
        // uri: '/hello'
        uri: 'hap://app/com.yzhj.yicaiyipu'
        // uri: 'hwfastapp://com.yzhj.yicaiyipu'
        });
        },
        click(event) {
        console.log(event,event.eventStatusCode);
        prompt.showToast({
        message: event.eventMessage
        });
        },
        turnTo() {
        router.push({
        uri: `/homePage?package='com.huawei.QuickAppDemo'`
        // uri: 'hap://app/com.huawei.QuickAppDemo'
        // uri: 'hwfastapp://com.yzhj.yicaiyipu'
        });
        },
        onBackPress () {
        console.log("back!!")
        var that = this
        shortcut.install({
        message: '我看你很喜欢这个应用呢，加个桌面再退出吧',
        success: function (ret) {
        console.log('添加成功');
        that.$app.exit()
        },
        fail: function (erromsg, errocode) {
        prompt.showToast({
        message: erromsg+errocode,
        duration: 2000,
        gravity: 'bottom'
        })
        }
        })
        return true
        },
        }
        </script>

父页面

<import name="shortcut" src="../Demo/demo.ux"></import>
<template>
<!-- Only one root node is allowed in template. -->
<div class="container">
<div>
<shortcut></shortcut>
</div>
</div>
</template>

<style>
  /* .container {
    flex-direction: column;
    justify-content:flex-end;
    align-items: center;
  }
</style>

<script>
  import shortcut from '@system.shortcut';
  import prompt from '@system.prompt';
  module.exports = {
    data: {
      componentData: {
        message: '点击跳转快应用',
      },
    },
    onInit() {
      this.$page.setTitleBar({
        text: '欢迎来到快应用',
        textColor: '#ffffff',
        backgroundColor: '#007DFF',
        backgroundOpacity: 0.5,
        menu: true
      });
    },
  }
</script>