How to prevent changing MatTab until confirmation?

I want to hold, the changing of MatTab until a confirmation is given. I have used MatDialog for confirmation. The issue is, before clicking "Yes", the the tab is already changed.

For example, From income tab, I click adjustment tab. And before switching to that tab, I need to show the popup first. But I am getting the popup after moving to adjustment tab.

component template:

 <mat-tab-group (click)="tabClick($event)">
  <mat-tab *ngFor="let tab of tabs; let index = index" [label]="tab">
    <app-spread></app-spread
  </mat-tab>
</mat-tab-group>

component ts (onClick's method):

tabClick(clickEvent: any) {
    if (clickEvent.target.innerText != 'First') {
      this.confirm();
    }
  }
  public async confirm() {
    const dialogRef = this.dialog.open(ConfirmationDialogComponent, {
      maxHeight: '200px',
      maxWidth: '767px',
      width: '360px',
      disableClose: true,
      data: {
        title: 'Confirmation Message',
        content:
          'There are valid statements that are not Final. Set the statements as Final?'
      }
    });
    const res = dialogRef.afterClosed().subscribe(result => {
      if (result === 1) {
        //TODO need to change the tab
      } else {
        //TODO no need to change the tab
      }
    });
  }

Sometime ago I simulate a "mat-tab" in this SO

I Imagine that you can use this with only change the function

<mat-tab-group #tabgroup style="margin-bottom:5px;" 
               animationDuration="0"   mat-align-tabs="start"
               (selectedIndexChange)="change(tabgroup,$event)">
...
</mat-tab-group>

And the function change:

  change(tab:any,index:number)
  {
    if (tab.selectedIndex!=this.indexOld){
      const dialogRef = this.dialog.open(....)
      const res = dialogRef.afterClosed().subscribe(result => {
        if (result === 1) {
           this.index=index;
        } else {
           tab.selectedIndex=this.indexOld;
        }
      });
    }
    else
    {
       this.index=index;
    }
  }

See the stackblitz -in the stackblitz I simple use the confirm dialog-

Update problem if we use a mat-dialog.

There's another approach that it's overwrite the behaviour of the mat-tab-group

We need change the _handleClick function of the mat-tab-group, (see this function in github) and the function _handleKeydown of the mat-header (see this function in github

It's a bit complex, but the only is get the mat-group using ViewChild (I use {static:true} because my tabgroup is visible always.

@ViewChild('tabgroup', { static: true }) tabgroup: MatTabGroup;

Then, in ngOnInit (if it's not static:true, we use ngAfterViewInit), simply redefine the function. for this first "cast" to any this.tabgroup

First we makes a function alertDialog

  alertDialog(index:number,tab:MatTab,tabHeader:any,)
  {
    const dialogRef = this.dialog.open(DialogOverviewExampleDialog, {
      data: {},
    });
    const res = dialogRef.afterClosed().subscribe((result) => {
      if (result) {
        tabHeader.focusIndex = index;

        if (!tab.disabled) {
          this.tabgroup.selectedIndex = index;
        }
      }
    });

  }

Then, in ngOnInit we write

ngOnInit(){
    (this.tabgroup as any)._handleClick = (
      tab: MatTab,
      tabHeader: any,
      index: number
    ) => {
      if (this.tabgroup.selectedIndex != index)
        this.alertDialog(index, tab, tabHeader);
    };
}

To override the _handleKeydown we are enclosed all in setTimeout to give time to Angular to paint the mat-tab-header

  ngOnInit() {
    ....
    setTimeout(() => {
      const tabHeader = (this.tabgroup as any)._tabHeader;
      tabHeader._handleKeydown = (event: KeyboardEvent) => {
        if (hasModifierKey(event)) {
          return;
        }

        switch (event.keyCode) {
          case ENTER:
          case SPACE:
            if (tabHeader.focusIndex !== tabHeader.selectedIndex) {
              const item = tabHeader._items.get(tabHeader.focusIndex);
              this.alertDialog(tabHeader.focusIndex, item, tabHeader);
            }
            break;
          default:
            tabHeader._keyManager.onKeydown(event);
        }
      };
    });

You can see in a new stackblit