关闭 InAppBrowser 后,我无法移动到下一页

After closing InAppBrowser, I am not able to move to next page

我一直面临 ionic 3 中的 inappbrowser 问题。在下面的代码中,如果付款成功,我想转到 Thankyoupage,否则它必须留在同一页面上。付款成功或失败后,关闭应用程序浏览器后,它会返回同一页面。我可以调用 this.navCtrl.push(ThankyouPage)。我看到未定义的异常。谁能指导我理解,我在哪里犯了错误

      let option = 'location=no,hidden=yes';
  let url = "https://www.example.com/pay;
  const browser = this.inappBrowser.create(url,option);
  browser.on('loadstart').subscribe(function(event) {  
    if(event.url== "https://www.example.net/success.php"){          
      browser.close();
      //failuring here
      this.navCtrl.push(ThankyouPage);
    }
    if(event.url== "https://www.example.net/failure.php"){          
      browser.close();          
    }        
  });
    let self=this;                            // add this line
    let option = 'location=no,hidden=yes';
  let url = "https://www.example.com/pay;
  const browser = this.inappBrowser.create(url,option);
  browser.on('loadstart').subscribe(function(event) {  
    if(event.url== "https://www.example.net/success.php"){          
      browser.close();
      //failuring here
      self.navCtrl.push(ThankyouPage);    // Update this statement 
   //self.navCtrl.push('ThankyouPage');    // Uncomment this if you use lazyloading
    }
    if(event.url== "https://www.example.net/failure.php"){          
      browser.close();          
    }        
  });