但实际上这些方法只能适配部分机型，而Google Nexus 5、 HTC 部分机型等手机使用这些代码都不能打开闪光灯。

察看Android开发者文档，在Camera的class overview中可以看到我们忽略掉的部分。

http://developer.android.com/intl/zh-cn/reference/android/hardware/Camera.html

To take pictures with this class, use the following steps:

1.Obtain an instance of Camera from open(int).
2.Get existing (default) settings with getParameters().
3.If necessary, modify the returned Camera.Parameters object and call setParameters(Camera.Parameters).
4.If desired, call setDisplayOrientation(int).
5.Important: Pass a fully initialized SurfaceHolder to setPreviewDisplay(SurfaceHolder). Without a surface, the camera will be unable to start the preview.
6.Important: Call startPreview() to start updating the preview surface. Preview must be started before you can take a picture.
7.When you want, call takePicture(Camera.ShutterCallback, Camera.PictureCallback, Camera.PictureCallback, Camera.PictureCallback) to capture a photo. Wait for the callbacks to provide the actual image data.
8.After taking a picture, preview display will have stopped. To take more photos, call startPreview() again first.
9.Call stopPreview() to stop updating the preview surface.
10.Important: Call release() to release the camera for use by other applications. Applications should release the camera immediately in onPause() (and re-open() it in onResume()).

看到第五点（important），如果没有在startPreview之前调用setPreviewDisplay。照相机就不会启动预览。

所以问题解决，适用于市面上大部分机型的相机开启，需要在startPreview之前setPreivewDisplay：

Camera.Parameters param = mCamera.getParameters();
param.setFlashMode(Parameters.FLASH_MODE_TORCH);
mCamera.setParameters(param);
mCamera.setPreviewDisplay(mHolder); //重要！在startPreview要调用
mCamera.startPreview();

为setPreviewDisplay(SurfaceHolder holder) 传入的SurfaceHolder参数需要在setPreviewDisplay前初始化完成：

private WindowManager mWindowManager;
private SurfaceHolder mHolder;
private MySurfaceView mFlashTorchSurface;private void createSurfaceView() {if (mFlashTorchSurface != null) {return;}try {mWindowManager = (WindowManager) mContext.getSystemService(Context.WINDOW_SERVICE); // 获取WindowManager// 添加手电筒所需要的SurfaceViewmFlashTorchSurface = new MySurfaceView(mContext);// 由于会在SurfaceView中进行预览，所以将背景色设置为黑色，使用户看不到mFlashTorchSurface.setBackgroundColor(Color.BLACK);WindowManager.LayoutParams mCallViewParams = new WindowManager.LayoutParams(); // 设置LayoutParams(全局变量）相关参数mCallViewParams.type = WindowManager.LayoutParams.TYPE_SYSTEM_ALERT;mCallViewParams.format = PixelFormat.RGBA_8888; // 设置透明背景mCallViewParams.width = 1;mCallViewParams.height = 1;mCallViewParams.gravity = Gravity.RIGHT | Gravity.TOP;mCallViewParams.flags = WindowManager.LayoutParams.FLAG_NOT_TOUCH_MODAL| WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE; // 让当前View失去焦点mWindowManager.addView(mFlashTorchSurface, mCallViewParams);} catch (Exception ex) {ex.printStackTrace();mFlashTorchSurface = null;}}/*** 手电筒需要的surface*/private class MySurfaceView extends SurfaceView implementsSurfaceHolder.Callback {public MySurfaceView(Context context) {super(context);initHolder();}private void initHolder() {// 注册surfaceCreated、surfaceChanged、surfaceDestroyed回调方法SurfaceHolder holder = getHolder();holder.addCallback(this);holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); // 在某些机型上，这一项必须设置}@Overridepublic void surfaceCreated(SurfaceHolder holder) {mHolder = holder;}@Overridepublic void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {}@Overridepublic void surfaceDestroyed(SurfaceHolder holder) {mHolder = null;}}

这样，大部分机型都可以打开手电筒了。

完整的打开关闭方法如下：

public void powerOn() {
//打开手电initCamera(); //初始化相机createSurfaceView();  //初始化SurfaceHoldersetLightOn(); //打开手电
}private void initCamera() {try {mCamera = Camera.open();} catch (Exception e) {mCamera = null;}if (mCamera == null) {mIsAvailable = false;} else {mIsAvailable = true;}
}private void setLightOn() {if (mCamera == null) {return;}try {// 防止startPreview、setParameters抛出RuntimeException异常导致崩溃Camera.Parameters param = mCamera.getParameters();param.setFlashMode(Parameters.FLASH_MODE_TORCH);mCamera.setParameters(param);mCamera.setPreviewDisplay(mHolder);mCamera.startPreview();} catch (Exception e) {powerOff();return;}
}public void powerOff() {
//关闭手电，手电使用结束后必须释放camera资源，否则会造成内存泄露setLightOff();//关灯并释放资源if (mCamera != null) { //保护mCamera.stopPreview();mCamera.release();mCamera = null;}removeSurfaceView(); //释放SurfaceHodler
}private void setLightOff() {if (mCamera == null) {return;}try {// 防止startPreview、setParameters抛出RuntimeException异常导致崩溃Camera.Parameters param = mCamera.getParameters();param.setFlashMode(Parameters.FLASH_MODE_OFF);mCamera.setParameters(param);mCamera.stopPreview();mCamera.release();} catch (RuntimeException e) {e.printStackTrace();mCamera.stopPreview();mCamera.release();}mCamera = null;mIsLight = false;
}private void removeSurfaceView() {if (mFlashTorchSurface != null) {mWindowManager.removeViewImmediate(mFlashTorchSurface);mFlashTorchSurface = null;}
}

当然还要加上相关权限：

<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.FLASHLIGHT" />

原地址：http://codesblock.com/blog/?p=56