fix(button-toggle): toggle group should not emit an initial change event.

src/lib/button-toggle/button-toggle.spec.ts

@@ -25,6 +25,7 @@ describe('MdButtonToggle', () => {
         ButtonTogglesInsideButtonToggleGroup,
         ButtonToggleGroupWithNgModel,
         ButtonTogglesInsideButtonToggleGroupMultiple,
+        ButtonToggleGroupWithInitialValue,
         StandaloneButtonToggle,
       ],
     });
@@ -320,6 +321,29 @@ describe('MdButtonToggle', () => {
       expect(testComponent.modelValue).toBe('red');
       expect(testComponent.lastEvent.value).toBe('red');
     }));
+
+  });
+
+  describe('with initial value and change event', () => {
+
+    it('should not fire an initial change event', async(() => {
+      let fixture = TestBed.createComponent(ButtonToggleGroupWithInitialValue);
+      let testComponent = fixture.debugElement.componentInstance;
+      let groupDebugElement = fixture.debugElement.query(By.directive(MdButtonToggleGroup));
+      let groupInstance: MdButtonToggleGroup = groupDebugElement.injector.get(MdButtonToggleGroup);
+
+      fixture.detectChanges();
+
+      expect(groupInstance.value).toBe('red');
+      expect(testComponent.lastEvent).toBeFalsy();
+
+      groupInstance.value = 'green';
+      fixture.detectChanges();
+
+      expect(groupInstance.value).toBe('green');
+      expect(testComponent.lastEvent.value).toBe('green');
+    }));
+
   });
 
   describe('inside of a multiple selection group', () => {
@@ -532,3 +556,15 @@ class ButtonTogglesInsideButtonToggleGroupMultiple {
   `
 })
 class StandaloneButtonToggle { }
+
+@Component({
+  template: `
+  <md-button-toggle-group (change)="lastEvent = $event" value="red">
+    <md-button-toggle value="red">Value Red</md-button-toggle>
+    <md-button-toggle value="green">Value Green</md-button-toggle>
+  </md-button-toggle-group>
+  `
+})
+class ButtonToggleGroupWithInitialValue {
+  lastEvent: MdButtonToggleChange;
+}

src/lib/button-toggle/button-toggle.ts

@@ -12,7 +12,8 @@ import {
     Output,
     QueryList,
     ViewEncapsulation,
-    forwardRef
+    forwardRef,
+    AfterViewInit
 } from '@angular/core';
 import {
     NG_VALUE_ACCESSOR,
@@ -55,7 +56,7 @@ export class MdButtonToggleChange {
     'role': 'radiogroup',
   },
 })
-export class MdButtonToggleGroup implements ControlValueAccessor {
+export class MdButtonToggleGroup implements AfterViewInit, ControlValueAccessor {
   /** The value for the button toggle group. Should match currently selected button toggle. */
   private _value: any = null;
 
@@ -68,6 +69,9 @@ export class MdButtonToggleGroup implements ControlValueAccessor {
   /** The currently selected button toggle, should match the value. */
   private _selected: MdButtonToggle = null;
 
+  /** Whether the button toggle group is initialized or not. */
+  private _isInitialized: boolean = false;
+
   /** The method to be called in order to update ngModel. */
   private _controlValueAccessorChangeFn: (value: any) => void = (value) => {};
 
@@ -84,6 +88,11 @@ export class MdButtonToggleGroup implements ControlValueAccessor {
   @ContentChildren(forwardRef(() => MdButtonToggle))
   _buttonToggles: QueryList<MdButtonToggle> = null;
 
+  /** TODO: internal */
+  ngAfterViewInit() {
+    this._isInitialized = true;
+  }
+
   @Input()
   get name(): string {
     return this._name;
@@ -114,7 +123,12 @@ export class MdButtonToggleGroup implements ControlValueAccessor {
       this._value = newValue;
 
       this._updateSelectedButtonToggleFromValue();
-      this._emitChangeEvent();
+
+      // Only emit a change event if the view is completely initialized.
+      // We don't want to emit a change event for the initial values.
+      if (this._isInitialized) {
+        this._emitChangeEvent();
+      }
     }
   }