Android如何打开闪光灯

在android中打开闪光灯的方法有两种，一种是获取硬件服务，通过反射的方式来操作闪光灯。另外一种是获得Camera对象，通过设置Camera的参数来操作闪光灯。一下是一个操作闪光灯的工具类：实现了两种方式操作闪光灯。通过switchFlashlight方法是通过反射的方式操作，通过turnLightOn，turnLightOff方法操作是通过设置Camera来操作闪关灯的。通过反射的方法貌似在4.0以上的版本中都不好用了，建议使用设置摄像头参数的方式来操作。
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原文：https://blog.csdn.net/mac_lim/article/details/8987377 
 

public class FlashlightManager {
	private static final String TAG = FlashlightManager.class.getSimpleName();
	private static final Object iHardwareService;
	private static final Method setFlashEnabledMethod;
	static {
		iHardwareService = getHardwareService();
		setFlashEnabledMethod = getSetFlashEnabledMethod(iHardwareService);
		if (iHardwareService == null) {
			Log.v(TAG, "This device does supports control of a flashlight");
		} else {
			Log.v(TAG, "This device does not support control of a flashlight");
		}
	}
	private FlashlightManager() {
	}
	private static Object getHardwareService() {
		Class<?> serviceManagerClass = maybeForName("android.os.ServiceManager");
		if (serviceManagerClass == null) {
			return null;
		}
		Method getServiceMethod = maybeGetMethod(serviceManagerClass,
				"getService", String.class);
		if (getServiceMethod == null) {
			return null;
		}
		Object hardwareService = invoke(getServiceMethod, null, "hardware");
		if (hardwareService == null) {
			return null;
		}
		Class<?> iHardwareServiceStubClass = maybeForName("android.os.IHardwareService$Stub");
		if (iHardwareServiceStubClass == null) {
			return null;
		}
		Method asInterfaceMethod = maybeGetMethod(iHardwareServiceStubClass,
				"asInterface", IBinder.class);
		if (asInterfaceMethod == null) {
			return null;
		}
		return invoke(asInterfaceMethod, null, hardwareService);
	}
	private static Method getSetFlashEnabledMethod(Object iHardwareService) {
		if (iHardwareService == null) {
			return null;
		}
		Class<?> proxyClass = iHardwareService.getClass();
		return maybeGetMethod(proxyClass, "setFlashlightEnabled", boolean.class);
	}
	private static Class<?> maybeForName(String name) {
		try {
			return Class.forName(name);
		} catch (ClassNotFoundException cnfe) {
			// OK
			return null;
		} catch (Exception re) {
			re.printStackTrace();
			Log.w(TAG, "Unexpected error while finding class " + name, re);
			return null;
		}
	}
	/**
	 * 通过设置Camera打开闪光灯
	 * @param mCamera
	 */
	public static void turnLightOn(Camera mCamera) {
		if (mCamera == null) {
			return;
		}
		Parameters parameters = mCamera.getParameters();
		if (parameters == null) {
			return;
		}
	List<String> flashModes = parameters.getSupportedFlashModes();
		// Check if camera flash exists
		if (flashModes == null) {
			// Use the screen as a flashlight (next best thing)
			return;
		}
		String flashMode = parameters.getFlashMode();
		Log.i(TAG, "Flash mode: " + flashMode);
		Log.i(TAG, "Flash modes: " + flashModes);
		if (!Parameters.FLASH_MODE_TORCH.equals(flashMode)) {
			// Turn on the flash
			if (flashModes.contains(Parameters.FLASH_MODE_TORCH)) {
				parameters.setFlashMode(Parameters.FLASH_MODE_TORCH);
				mCamera.setParameters(parameters);
			} else {
			}
		}
	}
	/**
	 * 通过设置Camera关闭闪光灯
	 * @param mCamera
	 */
	public static void turnLightOff(Camera mCamera) {
		if (mCamera == null) {
			return;
		}
		Parameters parameters = mCamera.getParameters();
		if (parameters == null) {
			return;
		}
		List<String> flashModes = parameters.getSupportedFlashModes();
		String flashMode = parameters.getFlashMode();
		// Check if camera flash exists
		if (flashModes == null) {
			return;
		}
		Log.i(TAG, "Flash mode: " + flashMode);
		Log.i(TAG, "Flash modes: " + flashModes);
		if (!Parameters.FLASH_MODE_OFF.equals(flashMode)) {
			// Turn off the flash
			if (flashModes.contains(Parameters.FLASH_MODE_OFF)) {
				parameters.setFlashMode(Parameters.FLASH_MODE_OFF);
				mCamera.setParameters(parameters);
			} else {
				Log.e(TAG, "FLASH_MODE_OFF not supported");
			}
		}
	}
	private static Method maybeGetMethod(Class<?> clazz, String name,
			Class<?>... argClasses) {
		try {
			return clazz.getMethod(name, argClasses);
		} catch (Exception nsme) {
			nsme.printStackTrace();
			// OK
			return null;
		}
	}
	private static Object invoke(Method method, Object instance, Object... args) {
		try {
			return method.invoke(instance, args);
		} catch (Exception e) {
			Log.w(TAG, "Unexpected error while invoking " + method, e);
			return null;
		}
	}
	/**
	 * 通过反射来操作闪光灯
	 * @param active
	 */
	public static void switchFlashlight(boolean active) {
		setFlashlight(active);
	}
	static void disableFlashlight() {
		setFlashlight(false);
	}
	private static void setFlashlight(boolean active) {
		if (iHardwareService != null) {
			invoke(setFlashEnabledMethod, iHardwareService, active);
		}
	}
}