6 使用触摸事件

示例 6-1 TouchImage 类定义

public static class TouchImage extends ImageView {
    private long touchId = -1;
    double touchx, touchy;

    public TouchImage(int x, int y, Image img) {
        super(img);
        setTranslateX(x);
        setTranslateY(y);
        setEffect(new DropShadow(8.0, 4.5, 6.5, Color.DARKSLATEGRAY));

        setOnTouchPressed(new EventHandler<TouchEvent>() {
            @Override public void handle(TouchEvent event) {
                if (touchId == -1) {
                    touchId = event.getTouchPoint().getId();
                    touchx = event.getTouchPoint().getSceneX() - getTranslateX();
                    touchy = event.getTouchPoint().getSceneY() - getTranslateY();
                }
                event.consume();
            }
        });

        setOnTouchReleased(new EventHandler<TouchEvent>() {
            @Override public void handle(TouchEvent event) {
                if (event.getTouchPoint().getId() == touchId) {
                    touchId = -1;
                }
                event.consume();
            }
        });

        setOnTouchMoved(new EventHandler<TouchEvent>() {
            @Override public void handle(TouchEvent event) {
                if (event.getTouchPoint().getId() == touchId) {
                    setTranslateX(event.getTouchPoint().getSceneX() - touchx);
                    setTranslateY(event.getTouchPoint().getSceneY() - touchy);
                }
                event.consume();
            }
        });
    }
}

示例 6-2 Ball 类定义

private static class Ball extends Circle {
    double touchx, touchy;

    public Ball(int x, int y) {
        super(35);

        RadialGradient gradient = new RadialGradient(0.8, -0.5, 0.5, 0.5, 1,
            true, CycleMethod.NO_CYCLE, new Stop [] {
                new Stop(0, Color.FIREBRICK),
                new Stop(1, Color.BLACK)
            });

        setFill(gradient);
        setTranslateX(x);
        setTranslateY(y);

        setOnTouchPressed(new EventHandler<TouchEvent>() {
            @Override public void handle(TouchEvent event) {
                if (event.getTouchCount() == 1) {
                    touchx = event.getTouchPoint().getSceneX() - getTranslateX();
                    touchy = event.getTouchPoint().getSceneY() - getTranslateY();
                    setEffect(new Lighting());
                }
                event.consume();
            }
        });

        setOnTouchReleased(new EventHandler<TouchEvent>() {
            @Override public void handle(TouchEvent event) {
                setEffect(null);
                event.consume();
            }
        });

        // 如果第一个手指触摸到球并且正在移动或静止，并且第二个手指触摸到一个矩形，则跳跃
        EventHandler<TouchEvent> jumpHandler = new EventHandler<TouchEvent>() {
            @Override public void handle(TouchEvent event) {

                if (event.getTouchCount() != 2) {
                    // 如果不是两个手指触摸，则忽略
                    return;
                }

                TouchPoint main = event.getTouchPoint();
                TouchPoint other = event.getTouchPoints().get(1);

                if (other.getId() == main.getId()) {
                    // 如果第二个手指在球内，而第一个手指在其他地方，则忽略
                    return;
                }

                if (other.getState() != TouchPoint.State.PRESSED ||
                    other.belongsTo(Ball.this) ||
                    !(other.getTarget() instanceof Rectangle) ){
                    // 只有当第二个手指刚刚按在矩形上时才跳跃
                    return;
                }

                // 现在跳跃
                setTranslateX(other.getSceneX() - touchx);
                setTranslateY(other.getSceneY() - touchy);

                // 抓住目标手指，它现在在球内，以便跳跃可以继续而不释放手指
                other.grab();

                // 原始触摸点不再重要，所以调用ungrab()释放目标
                main.ungrab();

                event.consume();
            }
        };

        setOnTouchStationary(jumpHandler);
        setOnTouchMoved(jumpHandler);
    }
}