fix(snack-bar): animation not starting for subsequent snack bars (#6649)

Since the switch to OnPush change detection, opening a snack bar while another one is open, programmatically isn't guaranteed to actually show the second snack bar, because the user might not hit the zone (e.g. if it's through a timeout). These changes trigger change detection manually on open. I also got rid of a couple of redundant methods on the snack bar container.

Fixes #6222.

src/lib/snack-bar/snack-bar-container.ts

@@ -17,6 +17,7 @@ import {
   ElementRef,
   ChangeDetectionStrategy,
   ViewEncapsulation,
+  ChangeDetectorRef,
 } from '@angular/core';
 import {
   trigger,
@@ -63,24 +64,25 @@ export const HIDE_ANIMATION = '195ms cubic-bezier(0.0,0.0,0.2,1)';
   },
   animations: [
     trigger('state', [
-      state('void', style({transform: 'translateY(100%)'})),
-      state('initial', style({transform: 'translateY(100%)'})),
+      state('void, initial, complete', style({transform: 'translateY(100%)'})),
       state('visible', style({transform: 'translateY(0%)'})),
-      state('complete', style({transform: 'translateY(100%)'})),
       transition('visible => complete', animate(HIDE_ANIMATION)),
       transition('initial => visible, void => visible', animate(SHOW_ANIMATION)),
     ])
   ],
 })
 export class MdSnackBarContainer extends BasePortalHost implements OnDestroy {
+  /** Whether the component has been destroyed. */
+  private _destroyed = false;
+
   /** The portal host inside of this container into which the snack bar content will be loaded. */
   @ViewChild(PortalHostDirective) _portalHost: PortalHostDirective;
 
   /** Subject for notifying that the snack bar has exited from view. */
-  private onExit: Subject<any> = new Subject();
+  _onExit: Subject<any> = new Subject();
 
   /** Subject for notifying that the snack bar has finished entering the view. */
-  private onEnter: Subject<any> = new Subject();
+  _onEnter: Subject<any> = new Subject();
 
   /** The state of the snack bar animations. */
   animationState: SnackBarState = 'initial';
@@ -91,7 +93,8 @@ export class MdSnackBarContainer extends BasePortalHost implements OnDestroy {
   constructor(
     private _ngZone: NgZone,
     private _renderer: Renderer2,
-    private _elementRef: ElementRef) {
+    private _elementRef: ElementRef,
+    private _changeDetectorRef: ChangeDetectorRef) {
     super();
   }
 
@@ -126,7 +129,7 @@ export class MdSnackBarContainer extends BasePortalHost implements OnDestroy {
     if (event.toState === 'visible') {
       // Note: we shouldn't use `this` inside the zone callback,
       // because it can cause a memory leak.
-      const onEnter = this.onEnter;
+      const onEnter = this._onEnter;
 
       this._ngZone.run(() => {
         onEnter.next();
@@ -137,30 +140,21 @@ export class MdSnackBarContainer extends BasePortalHost implements OnDestroy {
 
   /** Begin animation of snack bar entrance into view. */
   enter(): void {
-    this.animationState = 'visible';
-  }
-
-  /** Returns an observable resolving when the enter animation completes.  */
-  _onEnter(): Observable<void> {
-    this.animationState = 'visible';
-    return this.onEnter.asObservable();
+    if (!this._destroyed) {
+      this.animationState = 'visible';
+      this._changeDetectorRef.detectChanges();
+    }
   }
 
   /** Begin animation of the snack bar exiting from view. */
   exit(): Observable<void> {
     this.animationState = 'complete';
-    return this._onExit();
+    return this._onExit;
   }
 
-  /** Returns an observable that completes after the closing animation is done. */
-  _onExit(): Observable<void> {
-    return this.onExit.asObservable();
-  }
-
-  /**
-   * Makes sure the exit callbacks have been invoked when the element is destroyed.
-   */
+  /** Makes sure the exit callbacks have been invoked when the element is destroyed. */
   ngOnDestroy() {
+    this._destroyed = true;
     this._completeExit();
   }
 
@@ -171,7 +165,7 @@ export class MdSnackBarContainer extends BasePortalHost implements OnDestroy {
   private _completeExit() {
     // Note: we shouldn't use `this` inside the zone callback,
     // because it can cause a memory leak.
-    const onExit = this.onExit;
+    const onExit = this._onExit;
 
     first.call(this._ngZone.onMicrotaskEmpty).subscribe(() => {
       onExit.next();

src/lib/snack-bar/snack-bar-ref.ts

@@ -44,7 +44,7 @@ export class MdSnackBarRef<T> {
     this.containerInstance = containerInstance;
     // Dismiss snackbar on action.
     this.onAction().subscribe(() => this.dismiss());
-    containerInstance._onExit().subscribe(() => this._finishDismiss());
+    containerInstance._onExit.subscribe(() => this._finishDismiss());
   }
 
   /** Dismisses the snack bar. */
@@ -90,7 +90,7 @@ export class MdSnackBarRef<T> {
 
   /** Gets an observable that is notified when the snack bar has opened and appeared. */
   afterOpened(): Observable<void> {
-    return this.containerInstance._onEnter();
+    return this.containerInstance._onEnter;
   }
 
   /** Gets an observable that is notified when the snack bar action is called. */