Angular 4 Error: Expression has changed after it was checked

3
votes

I am using Angular Material in my Angular 4 app. When I try to use the MatSnackBar in the ngAfterViewInit(), I am facing an error as:

ExpressionChangedAfterItHasBeenCheckedError: Expression has changed after it was checked. Previous value: 'undefined'. Current value: 'visible-bottom'.It seems like the view has been created after its parent and its children have been dirty checked. Has it been created in a change detection hook ?

I have used the ChangeDetectorRef to detect the changes, but it doesn't seem to work.

Here's the code I have been working on: 

   constructor(private matSnackBar: MatSnackBar, private router: Router, private cdr: ChangeDetectorRef) { }

   ngOnInit() {}

   ngAfterViewInit() {
    let snackBarRef = this.matSnackBar.open('Redirecting to dashboard..', 'Cancel', {
      duration: 10000
    });

    snackBarRef.onAction().subscribe(() => {
      console.log("Cancelled");
    });


    this.cdr.detectChanges();
  }

Please help me resolve this issue.

2
javascriptangularangular-material2
Did you try moving this.cdr.detectChanges(); inside the onAction().subscribe(() => {}); - Amit Chigadani
@AmitChigadani That doesn't work! - starlight
Try to create a working plunker to replicate the error. Provided code won't help much. - Amit Chigadani

2 Answers

4
votes

One potential but crude solution is to use setTimeout - 

let snackBarRef;
setTimeout(() => {
    snackBarRef = this.matSnackBar.open('Redirecting to dashboard..', 'Cancel', {
      duration: 10000
    });
});

please refer https://github.com/angular/material2/issues/6158 for more information.

4
votes

Try to move snackbar in your constructor: 

constructor(private matSnackBar: MatSnackBar, private router: Router, private cdr: ChangeDetectorRef) {
  let snackBarRef = this.matSnackBar.open('Redirecting to dashboard..', 'Cancel', {
    duration: 10000
  });
  snackBarRef.onAction().subscribe(() => {
    console.log("Cancelled");
  });
}