How to open and close Angular mat menu on hover

Issue

This question is in reference to this Github issue, with mat-menu which can’t be toggled using mouse hover, I am basically trying to replace a bootstrap based horizontal navigation menu with angular material’s menu. The only thing keeping me from replicating bootstrap based menu is opening and closing mat-menu on hover.
As mentioned in the above Github issue there are some workarounds to achieve what I want, like using, mouseEnter

(mouseenter)="menuTrigger.openMenu()"

or adding a span inside Mat-menu in order to bind mat-menu close,

<mat-menu #menu="matMenu" overlapTrigger="false">
  <span (mouseleave)="menuTrigger.closeMenu()">
    <button mat-menu-item>Item 1</button>
    <button mat-menu-item>Item 2</button>
  </span>
</mat-menu>

but none of the solutions seems to cover every little scenario,

e.g.

As mentioned in the above Github issue, there are following issues in the first SO solution.

  • Hover the mouse cursor on the button and the menu will pop up. But if you click on the button, it will hide and show the menu. IMHO
    it’s a bug.
  • To hide the menu, the user needs to click outside of the menu. Ideally, the menu would become hidden if the mouse cursor is outside
    of the area (which includes the button, the menu, and sub-menus)
    longer than 400ms.

And in the span solution which tries to solve one of the above issues, but doesn’t work properly, e.g.

hovering over MatMenuTrigger does open the mat-menu as expected but if a user moves the mouse away without entering mat-menu, then it doesn’t close automatically which is wrong.

Also moving to one of the levels two sub-menu also closes the level one menu which is not what I want,

P.S moving mouse from one opened menu to the next sibling one doesn’t open the next one. I guess this might be difficult to achieve as mentioned here, But I think some of these might be achievable right?

Here is a basic stackBlitz which reproduces what I am experiencing, any help is appreciated.

Solution

The first challenge is that mat-menu steals the focus from the button when the CDK overlay is generated due to the z-index of the overlay… to solve this you need to set the z-index in a style for the button…

  • This will stop the recursive loop when you add a (mouseleave) to the button. style="z-index:1050"

Next you need to track the state of all enter and leave events for the levelone and levelTwo menu’s and store that state in two component variables.

enteredButton = false;
isMatMenuOpen = false;
isMatMenu2Open = false;

Next create menu enter and menuLeave methods for both menu levels.. notice menuLeave(trigger) checks if level2 is accessed and does nothing if true.

Please Note: menu2Leave() has logic to allow navigation back to level one but close both if exit the other side… also removing button focus upon leave of levels.

menuenter() {
    this.isMatMenuOpen = true;
    if (this.isMatMenu2Open) {
      this.isMatMenu2Open = false;
    }
  }

  menuLeave(trigger, button) {
    setTimeout(() => {
      if (!this.isMatMenu2Open && !this.enteredButton) {
        this.isMatMenuOpen = false;
        trigger.closeMenu();
        this.ren.removeClass(button['_elementRef'].nativeElement, 'cdk-focused');
        this.ren.removeClass(button['_elementRef'].nativeElement, 'cdk-program-focused');
      } else {
        this.isMatMenuOpen = false;
      }
    }, 80)
  }

  menu2enter() {
    this.isMatMenu2Open = true;
  }

  menu2Leave(trigger1, trigger2, button) {
    setTimeout(() => {
      if (this.isMatMenu2Open) {
        trigger1.closeMenu();
        this.isMatMenuOpen = false;
        this.isMatMenu2Open = false;
        this.enteredButton = false;
        this.ren.removeClass(button['_elementRef'].nativeElement, 'cdk-focused');
        this.ren.removeClass(button['_elementRef'].nativeElement, 'cdk-program-focused');
      } else {
        this.isMatMenu2Open = false;
        trigger2.closeMenu();
      }
    }, 100)
  }

  buttonEnter(trigger) {
    setTimeout(() => {
      if(this.prevButtonTrigger && this.prevButtonTrigger != trigger){
        this.prevButtonTrigger.closeMenu();
        this.prevButtonTrigger = trigger;
        trigger.openMenu();
      }
      else if (!this.isMatMenuOpen) {
        this.enteredButton = true;
        this.prevButtonTrigger = trigger
        trigger.openMenu()
      }
      else {
        this.enteredButton = true;
        this.prevButtonTrigger = trigger
      }
    })
  }

  buttonLeave(trigger, button) {
    setTimeout(() => {
      if (this.enteredButton && !this.isMatMenuOpen) {
        trigger.closeMenu();
        this.ren.removeClass(button['_elementRef'].nativeElement, 'cdk-focused');
        this.ren.removeClass(button['_elementRef'].nativeElement, 'cdk-program-focused');
      } if (!this.isMatMenuOpen) {
        trigger.closeMenu();
        this.ren.removeClass(button['_elementRef'].nativeElement, 'cdk-focused');
        this.ren.removeClass(button['_elementRef'].nativeElement, 'cdk-program-focused');
      } else {
        this.enteredButton = false;
      }
    }, 100)
  }

HTML

below is how to wire it all up.

<ng-container *ngFor="let menuItem of modulesList">

    <ng-container *ngIf="!menuItem.children">
        <a class="nav-link">
            <span class="icon fa" [ngClass]="menuItem.icon"></span>
      <span class="text-holder">{{menuItem.label}}</span>
    </a>
  </ng-container>
  <ng-container *ngIf="menuItem.children.length > 0">
    <button #button mat-button [matMenuTriggerFor]="levelOne" #levelOneTrigger="matMenuTrigger" (mouseenter)="levelOneTrigger.openMenu()" (mouseleave)="buttonLeave(levelOneTrigger, button)" style="z-index:1050">
      <span class="icon fa" [ngClass]="menuItem.icon"></span>
      <span>{{menuItem.label}}
        <i class="fa fa-chevron-down"></i>
      </span>
    </button>

    <mat-menu #levelOne="matMenu" direction="down" yPosition="below">
      <span (mouseenter)="menuenter()" (mouseleave)="menuLeave(levelOneTrigger, button)">
      <ng-container *ngFor="let childL1 of menuItem.children">
        <li class="p-0" *ngIf="!childL1.children" mat-menu-item>
          <a class="nav-link">{{childL1.label}}
            <i *ngIf="childL1.icon" [ngClass]="childL1.icon"></i>
          </a>
        </li>
        <ng-container *ngIf="childL1.children && childL1.children.length > 0">
          <li mat-menu-item #levelTwoTrigger="matMenuTrigger" [matMenuTriggerFor]="levelTwo">
            <span class="icon fa" [ngClass]="childL1.icon"></span>
            <span>{{childL1.label}}</span>
          </li>

          <mat-menu #levelTwo="matMenu">
            <span (mouseenter)="menu2enter()" (mouseleave)="menu2Leave(levelOneTrigger,levelTwoTrigger, button)">
            <ng-container *ngFor="let childL2 of childL1.children">
              <li class="p-0" mat-menu-item>
                <a class="nav-link">{{childL2.label}}
                  <i *ngIf="childL2.icon" [ngClass]="childL2.icon"></i>
                </a>
              </li>
            </ng-container>
            </span>
          </mat-menu>
        </ng-container>
      </ng-container>
      </span>
    </mat-menu>
  </ng-container>

</ng-container>

Stackblitz

https://stackblitz.com/edit/mat-nested-menu-yclrmd?embed=1&file=app/nested-menu-example.html

Answered By – Marshal

Answer Checked By – Jay B. (AngularFixing Admin)

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