Ionic - Uncaught (in promise): TypeError: Cannot read property 'then' of undefined

Question

我在 Ionic 应用程序运行时遇到此错误。我正在尝试实现 Ionic“Email Composer”库以从客户端发送电子邮件，请参考此 link 以了解我正在关注的代码； https://ionicframework.com/docs/native/email-composer。错误的流程是当我测试应用程序时，我点击了一个触发“LoadingDialog”函数的按钮，这个函数触发了“SendEmail”函数，这是错误发生的地方。我不确定如何修复此错误，但我认为它与我尚不理解的承诺语法有关。感谢您提供的任何帮助！

错误中出现的代码行

this.emailComposer.isAvailable().then((available: boolean) =>{ //<<<<<<<< THIS IS LINE 221 IN home.page.ts file and it appears in the error

this.SendEmail(); //<<<<<<<< THIS IS LINE 109 IN home.page.ts file

错误

ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'then' of undefined   TypeError: Cannot read property 'then' of undefined
     at HomePage.SendEmail (home.page.ts:221)
     at HomePage.<anonymous> (home.page.ts:109)
     at Generator.next (<anonymous>)
     at fulfilled (tslib.es6.js:70)
     at ZoneDelegate.invoke (zone-evergreen.js:359)
     at Object.onInvoke (core.js:34201)
     at ZoneDelegate.invoke (zone-evergreen.js:358)
     at Zone.run (zone-evergreen.js:124)
     at zone-evergreen.js:855
     at ZoneDelegate.invokeTask (zone-evergreen.js:391)
     at resolvePromise (zone-evergreen.js:797)
     at zone-evergreen.js:707
     at fulfilled (tslib.es6.js:70)
     at ZoneDelegate.invoke (zone-evergreen.js:359)
     at Object.onInvoke (core.js:34201)
     at ZoneDelegate.invoke (zone-evergreen.js:358)
     at Zone.run (zone-evergreen.js:124)
     at zone-evergreen.js:855
     at ZoneDelegate.invokeTask (zone-evergreen.js:391)
     at Object.onInvokeTask (core.js:34182)

代码 (home.page.ts)

            import { EmailComposer } from '@ionic-native/email-composer/ngx';
    
            export class HomePage {
    
            constructor(private http: Http, public loadingController: LoadingController,
                    public alertController: AlertController, 
                    private emailComposer: EmailComposer) {
           //constructor
            }
        async LoadingDialog(httpformdata) {//loading circle symbol
            const loading = await this.loadingController.create({
                message: 'Please wait...',
                duration: null
            });
            this.loading = loading;
            this.loading.present();
            console.log('ion dialog created.');
            /***  SendEmail  ***/
            this.SendEmail(); //<<<<<<<< THIS IS LINE 109 IN home.page.ts file
            /***  GET REQUEST  ***/
            this.GET_request(httpformdata);
            /***  POST REQUEST  ***/
            //this.POST_request(httpformdata);
            console.log('request made in async.');
            
            //this.loading.dismiss();
            //console.log('ion dialog dismissed.');
    
            const { role, data } = await loading.onDidDismiss();
    
            console.log('Loading dismissed!');
        }
            async RegularAlert(the_header: String, the_message: String) {//customized alert() dialog
            const alert = await this.alertController.create({
                header: '' + the_header,
                message: '' + the_message,
                buttons: ['OK']
            });
            await alert.present();
            return alert.getAttribute("header");
        }
    
        SendEmail(){
                this.emailComposer.isAvailable().then((available: boolean) =>{  //<<<<<<<< THIS IS LINE 221 IN home.page.ts file
                    if(available) {
                    //Now we know we can send
                    this.RegularAlert("testing the isAvailable().then", "available is true");//print a debug message to test functionality of   
    
                    let email = {
                        to:'max@mustermann.de',
                        cc: 'erika@mustermann.de',
                        bcc: [],
                        attachments: [],
                        subject: 'Cordova Icons',
                        body: 'How are you? Nice greetings from Leipzig',
                        isHtml: false
                      }
                    
                      // Send a text message using default options
                      this.emailComposer.open(email);
                    }
                    else{
                        this.RegularAlert("testing the isAvailable().then", "available is false");
                    }
                });
            
        } 
    
    }

Answer 1

我不确定您是否找到了问题的根源。但是这个问题与你的环境有关，你需要在你的模拟器/phone中测试以避免这个异常。

Answer 2

发生此错误是因为我没有运行模拟器中或 Android phone 上的应用程序，因为 Cordova 库仅运行具有移动 OS 就像 Android OS，所以 this.emailComposer.isAvailable() 是未定义的，而不是返回一个承诺。您至少需要：

if (this.platform.is('cordova')){ //run your email composer code here }

在我运行 android phone:

上的代码后，此代码对我有用

if (this.platform.is('cordova')){//use cordova for android,iOS,Windows-Mobile,etc
                this.emailComposer.isAvailable().then((available: 
                   boolean) =>{
                                //CODE HERE
                  
                            });
}else{
      console.log("Platform is not cordova/mobile","You are running in browser, this.emailComposer.isAvailable() is undefined.");
}

这是电子邮件编辑器的源代码：https://ionicframework.com/docs/native/email-composer

Ionic - Uncaught (in promise): TypeError: Cannot read property 'then' of undefined

Ionic - Uncaught (in promise): TypeError: Cannot read property 'then' of undefined

angular

ionic-framework

promise

angular-promise

错误中出现的代码行

错误

代码 (home.page.ts)