Resolved Issue #1242: Add Page showingModally event.

ui/page/page-common.ts

@@ -35,6 +35,7 @@ export class Page extends ContentView implements dts.Page {
     public static navigatingFromEvent = "navigatingFrom";
     public static navigatedFromEvent = "navigatedFrom";
     public static shownModallyEvent = "shownModally";
+    public static showingModallyEvent = "showingModally";
 
     protected _closeModalCallback: Function;
 
@@ -251,6 +252,13 @@ export class Page extends ContentView implements dts.Page {
         });
     }
 
+    protected _raiseShowingModallyEvent() {
+        this.notify({
+            eventName: Page.showingModallyEvent,
+            object: this
+        });
+    }
+
     public _getStyleScope(): styleScope.StyleScope {
         return this._styleScope;
     }

ui/page/page.android.ts

@@ -125,8 +125,9 @@ export class Page extends pageCommon.Page {
         this._dialogFragment = new DialogFragmentClass(this, fullscreen, function () {
             that.closeModal();
         });
-        this._dialogFragment.show(parent.frame.android.activity.getFragmentManager(), "dialog");
 
+        super._raiseShowingModallyEvent();
+        this._dialogFragment.show(parent.frame.android.activity.getFragmentManager(), "dialog");
         super._raiseShownModallyEvent(parent, context, closeCallback);
     }
 

ui/page/page.d.ts

@@ -61,6 +61,11 @@ declare module "ui/page" {
          */
         public static actionBarHiddenProperty: dependencyObservable.Property;
 
+        /**
+         * String value used when hooking to showingModally event.
+         */
+        public static showingModallyEvent: string;
+
         /**
          * String value used when hooking to shownModally event.
          */
@@ -159,7 +164,12 @@ declare module "ui/page" {
         on(event: "navigatedFrom", callback: (args: NavigatedData) => void, thisArg?: any);
         
         /**
-         * Raised when the page is shown as a modal dialog.
+         * Raised before the page is shown as a modal dialog.
+         */
+        on(event: "showingModally", callback: (args: observable.EventData) => void, thisArg?: any);
+
+        /**
+         * Raised after the page is shown as a modal dialog.
          */
         on(event: "shownModally", callback: (args: ShownModallyData) => void, thisArg?: any);
 

ui/page/page.ios.ts

@@ -241,6 +241,7 @@ export class Page extends pageCommon.Page {
             this._UIModalPresentationFormSheet = true;
         }
 
+        super._raiseShowingModallyEvent();
         var that = this;
         parent.ios.presentViewControllerAnimatedCompletion(this._ios, false, function completion() {
             that._raiseShownModallyEvent(parent, context, closeCallback);