Unity3D：Button保持状态

实现三个Button，三选一，其中一个选中状态，其他的normal状态。奇怪的解决方式。

参考链接：http://stackoverflow.com/questions/33770698/unity-5-ngui-highlighted-sprite-button-script-issue

    private void setUI_bottom(EN_PRINT_QUALITY printQuality){
        switch (printQuality) {
        case EN_PRINT_QUALITY.HIGH_SPEED:
            btn_highSpeed.interactable = false;
            btn_standard.interactable = true;
            btn_highQuality.interactable = true;
            break;
        case EN_PRINT_QUALITY.STANDARD:
            btn_highSpeed.interactable = true;
            btn_standard.interactable = false;
            btn_highQuality.interactable = true;
            break;
        case EN_PRINT_QUALITY.HIGH_QUALITY:
            btn_highSpeed.interactable = true;
            btn_standard.interactable = true;
            btn_highQuality.interactable = false;
            break;
        }
    }