public class FlashUtils {

  private static FlashUtils utils;
  private static Camera camera;
  public static boolean mIsOpen = true;

  //使用單例模式在這里初始化相機
  public static FlashUtils getInstance() {
    if (utils == null) {
      utils = new FlashUtils();
    }
    try {
      if (camera == null) {
        camera = Camera.open();
      }
    } catch (Exception e) {
      if (camera != null) {
        camera.release();
      }
      camera = null;
    }
    return utils;
  }

  //參考二維碼工具的閃光燈
  public void switchFlash() {
    try {
      Parameters parameters = camera.getParameters();
      if (mIsOpen) {
        if (parameters.getFlashMode().equals("torch")) {
          return;
        } else {
          parameters.setFlashMode("torch");
        }
      } else {
        if (parameters.getFlashMode().equals("off")) {
          return;
        } else {
          parameters.setFlashMode("off");
        }
      }
      camera.setParameters(parameters);
    } catch (Exception e) {
      finishFlashUtils();
    }
    mIsOpen = !mIsOpen;
  }

  //頁面銷毀的時候調用此方法
  public void finishFlashUtils() {
    if (camera != null) {
      camera.stopPreview();
      camera.release();
    }
    camera = null;
  }

}