处理400后运行时错误 [英] Runtime Error after handling 400

问题描述

场景：

使用WebApi 2令牌身份验证对用户名和密码进行身份验证。如果凭据正确，则返回令牌。但是，如果凭据不正确，则返回400错误请求。在我的Ionic 2项目中，如果我收到回复，我会导航到下一页。如果我收到错误消息，则会显示自定义错误消息。

The username and password is authenticated using WebApi 2 token authentication. If the credentials are correct, then token is returned. But, if the credentials are incorrect, 400 bad request is returned. In my Ionic 2 project, if I get the response, I navigate to the next page. If I get the error, I show my custom error message.

问题：

我面临的问题是，如果我第一次输入错误的凭据，则会显示自定义错误消息。如果我再次输入错误的凭据，则会显示自定义错误消息以及离子错误消息。

The issue I'm facing is, if I enter the wrong credentials for the first time, the custom error message is shown. If I enter wrong credentials again, the custom error message is shown along with the ionic error message.

这是我的代码：

login.ts

  doLogin() {
    if (this.Username !== undefined && this.Password !== undefined) {
      this.loading.present();
      this.authSrv.login(this.Username, this.Password).subscribe(data => {
        this.navCtrl.setRoot('HomePage');
        this.loading.dismiss();
      }, (err) => {
        this.errorMsg("Invalid Username/Password !" + err);
        this.loading.dismiss();
      });
    }
    else
      this.errorMsg("Please enter Username/Password");
  }

auth-service.ts

auth-service.ts

  login(username, password) {
    let headers = new Headers();
    headers.append('Content-Type', 'application/x-www-form-urlencoded');
    let urlSearchParams = new URLSearchParams();
    urlSearchParams.append('username', username);
    urlSearchParams.append('password', password);
    urlSearchParams.append('grant_type', 'password');
    let body = urlSearchParams.toString()
    return this.http.post('http://' + this._api + '/postoken', body, { headers: headers }
    )
      .map(res => res.json())
      .map((res) => {
        if (res !== null) {
          localStorage.setItem('acess_token', res["access_token"]);
          localStorage.setItem('access_type', res["access_type"]);
          localStorage.setItem('expires_in', res["expires_in"]);
          this.loggedIn = true;
        }
        return res;
      });
  }

截屏：

错误

任何建议都会有所帮助。

Any advice would be helpful.

推荐答案

LoadingController 只能被调用一次。

请注意，在组件被解除后，它将不再可用，并且必须创建另一个组件。

Note that after the component is dismissed, it will not be usable anymore and another one must be created.

这导致异常。
您应该每次在 doLogin 中创建新的加载。

This is causing the exception. You should create new loading everytime in doLogin.

doLogin() {
    if (this.Username !== undefined && this.Password !== undefined) {
      this.loading = this.loadingCtrl.create({ //create here
    content: 'Please wait...'
     });
      this.loading.present();
      this.authSrv.login(this.Username, this.Password).subscribe(data => {
        this.navCtrl.setRoot('HomePage');
        this.loading.dismiss();
      }, (err) => {
        this.errorMsg("Invalid Username/Password !" + err);
        this.loading.dismiss();
      });
    }
    else
      this.errorMsg("Please enter Username/Password");
  }

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