Input l disabled

[tribal heart]

Why are you binding on group's click event?
When do you want input's disabled turn to on?

and how do you want it to be enabled again?

ok, but once you press one of the button, how do you go back to enabled?

And do you need it multiple selectable?

try this

<div>
  <mat-form-field>
    <input matInput #filterBox [disabled]="toggleButtons.selected.length>0" />
    <mat-label>Filter</mat-label>
  </mat-form-field>
</div>

<mat-button-toggle-group #toggleButtons="matButtonToggleGroup" multiple>
  <mat-button-toggle value="TEST1">TEST1</mat-button-toggle>
  <mat-button-toggle value="TEST2">TEST2</mat-button-toggle>
</mat-button-toggle-group>

Please create a stackblitz reproduction.

[tribal heart]

Sorry but webcontainer are too memory hungry for me.

<div>
  <mat-form-field>
    <input matInput #filterBox [disabled]="!!toggleButtons.value.length" />
    <mat-label>Filter</mat-label>
  </mat-form-field>
</div>

<mat-button-toggle-group #toggleButtons="matButtonToggleGroup" multiple>
  <mat-button-toggle value="TEST1">TEST1</mat-button-toggle>
  <mat-button-toggle value="TEST2">TEST2</mat-button-toggle>
</mat-button-toggle-group>

Post the interesting part of code from your app

The group

Why the click handler again?

Please copy paste the template

The html

Now post the input part

Are them in the same html file?
Could you post it in its entirety?