5, 文字左右移动

class Main extends egret.DisplayObjectContainer {

    /**
     * 入口文件, 最先执行的构造方法
     * 这会实例化一个和手机屏幕一样大的舞台
     */
    public constructor() {
        super();
        this.once( egret.Event.ADDED_TO_STAGE, this.begin, this );
    }

    /**
     * 入口文件加载成功后执行的方法
     * 也是逻辑的开始, 通过触摸移动显示对象
     */
    private begin(event:egret.Event) {
        /**
         * 创建一个文本框,设定一个 scrollRect 限制显示范围
         * text: 文字内容
         * scrollRect: 显示范围
         * cacheAsBitmap: 是否缓存显示对象
         */
        var bigText: egret.TextField = new egret.TextField();
        bigText.text = "平移和滚动显示对象,平移和滚动显示对象";
        bigText.scrollRect = new egret.Rectangle(0, 0, 640, 50);
        bigText.cacheAsBitmap = true;
        bigText.x = 0;
        bigText.y = 10;
        this.addChild(bigText);

        /**
         * 创建一个左移, 一个右移 按钮
         * ev.currentTarget 获取触发事件的对象名
         */
        var btnLeft: egret.Shape = new egret.Shape();
        btnLeft.graphics.beginFill(0xcccc01);
        btnLeft.graphics.drawRect(0, 0, 50, 50);
        btnLeft.graphics.endFill();
        btnLeft.x = 50;
        btnLeft.y = 100;
        this.addChild(btnLeft);
        btnLeft.touchEnabled = true;
        btnLeft.addEventListener(egret.TouchEvent.TOUCH_TAP, onScroll, this);
        var btnRight: egret.Shape = new egret.Shape();
        btnRight.graphics.beginFill(0x01cccc);
        btnRight.graphics.drawRect(0,0,50,50);
        btnRight.graphics.endFill();
        btnRight.x = 150;
        btnRight.y = 100;
        this.addChild(btnRight);
        btnRight.touchEnabled = true;
        btnRight.addEventListener(egret.TouchEvent.TOUCH_TAP, onScroll, this);
        function onScroll(ev: egret.TouchEvent): void {
            var rect: egret.Rectangle = bigText.scrollRect;
            switch (ev.currentTarget) {
                case btnLeft:
                    rect.x += 20;
                    break;
                case btnRight:
                    rect.x -= 20;
                    break;
            }
            bigText.scrollRect = rect;
        }
    }

}