功能不会停止运行角度5

Question

我有点麻烦，我无法弄清楚我哪里出错......

我有一个从数据库中获取用户个人资料图片的功能，如此...

userPic(userId) {
    this._profileService.getProfilePictureByUserId(userId).subscribe(result => {
    return 'data:image/jpeg;base64,' + result.profilePicture;
  });
}

然后在我的HTML中

<div *ngFor="let data of returnedData">
<img [src]="userPic(data.lastModifiedUser.id)" alt="User Profile Picture">
</div>

所以我在数据数组中找回了99个对象，因此循环99次

但每次我运行我的应用程序时都会发生这种情况 我的应用程序崩溃了...我不知道我做错了什么？

修改

我试过这样做......

<div *ngFor="let data of data; let i = index; trackBy: trackByFn">
    <img [src]="userPic(angel.lastModifiedUser.id)" alt="User Profile Picture">
</div>

component.ts

userPic(userId) {
  this._profileService.getProfilePictureByUserId(userId).subscribe(result => 
{
    return 'data:image/jpeg;base64,' + result.profilePicture;
  });
}

trackByFn(index: any , item: any) {
    return index;
}

但应用程序仍在崩溃

Answer 1

返回Observable<string>并在async属性中使用[src]管道，并在trackby指令中使用*ngFor

userPic(profilePictureId, userId): Observable<string> {
    if (profilePictureId && userId && this.tenantId) {
      console.log('getprofilepicture');
      return this._profileService.getFriendProfilePictureById(profilePictureId, userId, this.tenantId).pipe(map(result => {
        if (result && result.profilePicture) {
            return '../../../assets/img/default-profile-picture.png';
            // return 'data:image/jpeg;base64,' + result.profilePicture;
        } else {
          return '../../../assets/img/default-profile-picture.png';
        }
    }));
    } else {
      console.log('didnt run');
      return Observable.of('../../../assets/img/default-profile-picture.png');
    }
  }

trackByFnById(index, item) {
    return item.lastModifiedUser.id;
}

模板

<div *ngFor="let data of returnedData; trackBy: trackByFnById">
    <img [src]="userPic(data.lastModifiedUser.profilePictureGuid, data.lastModifiedUser.id) | async" alt="User Profile Picture">
</div>

请记住导入必要的模块和库。

Answer 2

我建议你将async方法移动到你的组件并将你调用的图片保存到一个新的数组中，然后像你这样在你的html中循环：

private dataset = []; // guessing this is already populated with user information
public userPics = []; // use this to store your user pictures

private getUserPics(): void { // call this after you have filled you dataset with user information if that would be in your ngOnInit() or some other method
  for (const id of this.dataset) {
    this._profileService.getProfilePictureByUserId(id)
      .subscribe(
        res => { this.userPics.push('data:image/jpeg;base64,' + res.profilePicture); },
        err => { console.log(err); }
      );
  }
}

<div *ngFor="let pic of userPics">
  <img [src]="pic" alt="User Profile Picture">
</div>

您可能还想发布_profileService.getProfilePictureByUserId（）函数代码，这可能会导致您遇到问题。