NativeScript/tns-core-modules/ui/scroll-view/scroll-view-common.ts

import { ScrollView as ScrollViewDefinition, Orientation, ScrollEventData } from ".";
import { ContentView, Property, makeParser, makeValidator, EventData, booleanConverter, CSSType } from "../content-view";
import { profile } from "../../profiling";

export * from "../content-view";

@CSSType("ScrollView")
export abstract class ScrollViewBase extends ContentView implements ScrollViewDefinition {
    private _scrollChangeCount: number = 0;
    public static scrollEvent = "scroll";

    public orientation: Orientation;
    public scrollBarIndicatorVisible: boolean;
    public isScrollEnabled: boolean;

    public addEventListener(arg: string, callback: any, thisArg?: any) {
        super.addEventListener(arg, callback, thisArg);

        if (arg === ScrollViewBase.scrollEvent) {
            this._scrollChangeCount++;
            this.attach();
        }
    }

    public removeEventListener(arg: string, callback: any, thisArg?: any) {
        super.removeEventListener(arg, callback, thisArg);

        if (arg === ScrollViewBase.scrollEvent) {
            this._scrollChangeCount--;
            this.dettach();
        }
    }

    @profile
    public onLoaded() {
        super.onLoaded();

        this.attach();
    }

    public onUnloaded() {
        super.onUnloaded();

        this.dettach();
    }

    private attach() {
        if (this._scrollChangeCount > 0 && this.isLoaded) {
            this.attachNative();
        }
    }

    private dettach() {
        if (this._scrollChangeCount === 0 && this.isLoaded) {
            this.dettachNative();
        }
    }

    protected attachNative() {
        //
    }

    protected dettachNative() {
        //
    }

    get horizontalOffset(): number {
        return 0;
    }

    get verticalOffset(): number {
        return 0;
    }

    get scrollableWidth(): number {
        return 0;
    }

    get scrollableHeight(): number {
        return 0;
    }

    public abstract scrollToVerticalOffset(value: number, animated: boolean);
    public abstract scrollToHorizontalOffset(value: number, animated: boolean);
    public abstract _onOrientationChanged();
}
export interface ScrollViewBase {
    on(eventNames: string, callback: (data: EventData) => void, thisArg?: any);
    on(event: "scroll", callback: (args: ScrollEventData) => void, thisArg?: any);
}

const converter = makeParser<Orientation>(makeValidator("horizontal", "vertical"));
export const orientationProperty = new Property<ScrollViewBase, Orientation>({
    name: "orientation", defaultValue: "vertical", affectsLayout: true,
    valueChanged: (target: ScrollViewBase, oldValue: Orientation, newValue: Orientation) => {
        target._onOrientationChanged();
    },
    valueConverter: converter
});
orientationProperty.register(ScrollViewBase);

export const scrollBarIndicatorVisibleProperty = new Property<ScrollViewBase, boolean>({
    name: "scrollBarIndicatorVisible", defaultValue: true,
    valueConverter: booleanConverter
});
scrollBarIndicatorVisibleProperty.register(ScrollViewBase);

export const isScrollEnabledProperty = new Property<ScrollViewBase, boolean>({
    name: "isScrollEnabled", defaultValue: true,
    valueConverter: booleanConverter
});
isScrollEnabledProperty.register(ScrollViewBase);