在做项目的时候，遇到了打开手电筒的功能。本来在网上相应的代码已经很多，便拿过用了。但是在测试阶段发现各种各样的问题。无论是国产的手机，还是三星的手机。并且随着系统的不同，也有着这种各样的差异。
今天就对这个问题进行统一的整理。
一、4.4及其以下：
1、 打开手电筒：
private static Camera camera;
public static void flashLight(final Context context) {
try {
if (camera != null) {
camera.release();
camera = null;
}
camera = Camera.open();
Camera.Parameters param = camera.getParameters();
param.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
camera.setParameters(param);
camera.setPreviewTexture(new SurfaceTexture(0));
camera.startPreview();
}
} catch (Exception e) {
e.printStackTrace();
}
}2、关闭手电筒：
public static void closeFlashLight(final Context context) {
try {
if (camera == null) {
camera = Camera.open();
}
Camera.Parameters parameters = camera.getParameters();
parameters.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
camera.setParameters(parameters);
camera.stopPreview();
camera.release();
camera = null;
}
} catch (Exception e) {
}
}3、其中：
（1）camera.setPreviewTexture(new SurfaceTexture(0)); 这行代码是为了适配三星的手机。
（2）每一次关闭手电筒后，要对camera 进行释放。
二、Android 5.0 系统在Camera 方面做了很大的改动，废弃掉了Camera类。引入了Camera2 、CameraManager，用于管理摄像头，以便于更好的处理多个摄像头的问题。 具体的细节问题，可以去看其源码。
import android.content.Context;
import android.graphics.SurfaceTexture;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraDevice.StateCallback;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CameraMetadata;
import android.hardware.camera2.CaptureRequest;
import android.os.Handler;
import android.os.HandlerThread;
import android.os.Process;
import android.util.Log;
import android.util.Size;
import android.view.Surface;
import java.util.ArrayList;
/** * Manages the flashlight. */
public class FlashlightController {
private static final String TAG = "FlashlightController";
private static final boolean DEBUG = Log.isLoggable(TAG, Log.DEBUG);
private static final int DISPATCH_ERROR = 0;
private static final int DISPATCH_OFF = 1;
private static final int DISPATCH_AVAILABILITY_CHANGED = 2;
private final CameraManager mCameraManager;
private Handler mHandler;
private final ArrayList<FlashlightListener> mListeners = new ArrayList<FlashlightListener>(1);
private boolean mFlashlightEnabled;
private String mCameraId;
private boolean mCameraAvailable;
private CameraDevice mCameraDevice;
private CaptureRequest mFlashlightRequest;
private CameraCaptureSession mSession;
private SurfaceTexture mSurfaceTexture;
private Surface mSurface;
public FlashlightController(Context mContext) {
mCameraManager = (CameraManager) mContext.getSystemService(Context.CAMERA_SERVICE);
initialize();
}
public void initialize() {
try {
mCameraId = getCameraId();
} catch (Throwable e) {
LogUtil.e(TAG, "Couldn't initialize.", e);
return;
}
if (mCameraId != null) {
ensureHandler();
mCameraManager.registerAvailabilityCallback(mAvailabilityCallback, mHandler);
}
}
public synchronized void setFlashlight(boolean enabled) {
if (mFlashlightEnabled != enabled) {
mFlashlightEnabled = enabled;
postUpdateFlashlight();
}
}
public void killFlashlight() {
boolean enabled;
synchronized (this) {
enabled = mFlashlightEnabled;
}
if (enabled) {
mHandler.post(mKillFlashlightRunnable);
}
}
public synchronized boolean isAvailable() {
return mCameraAvailable;
}
public void addListener(FlashlightListener l) {
synchronized (mListeners) {
cleanUpListenersLocked(l);
mListeners.add(l);
}
}
public void removeListener(FlashlightListener l) {
synchronized (mListeners) {
cleanUpListenersLocked(l);
}
}
private synchronized void ensureHandler() {
if (mHandler == null) {
HandlerThread thread = new HandlerThread(TAG, Process.THREAD_PRIORITY_BACKGROUND);
thread.start();
mHandler = new Handler(thread.getLooper());
}
}
private void startDevice() throws CameraAccessException {
mCameraManager.openCamera(getCameraId(), new StateCallback() {
@Override
public void onOpened(CameraDevice camera) {
mCameraDevice = camera;
postUpdateFlashlight();
}
@Override
public void onDisconnected(CameraDevice camera) {
if (mCameraDevice == camera) {
dispatchOff();
teardown();
}
}
@Override
public void onError(CameraDevice camera, int error) {
LogUtil.e(TAG, "Camera error: camera=" + camera + " error=" + error);
if (camera == mCameraDevice || mCameraDevice == null) {
handleError();
}
}
}, mHandler);
}
private void startSession() throws CameraAccessException {
mSurfaceTexture = new SurfaceTexture(0,false);
Size size = getSmallestSize(mCameraDevice.getId());
mSurfaceTexture.setDefaultBufferSize(size.getWidth(), size.getHeight());
mSurface = new Surface(mSurfaceTexture);
ArrayList<Surface> outputs = new ArrayList<Surface>(1);
outputs.add(mSurface);
mCameraDevice.createCaptureSession(outputs, new android.hardware.camera2.CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(CameraCaptureSession session) {
mSession = session;
postUpdateFlashlight();
}
@Override
public void onConfigureFailed(CameraCaptureSession session) {
LogUtil.e(TAG, "Configure failed.");
if (mSession == null || mSession == session) {
handleError();
}
}
}, mHandler);
}
private Size getSmallestSize(String cameraId) throws CameraAccessException {
Size[] outputSizes = mCameraManager.getCameraCharacteristics(cameraId)
.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP)
.getOutputSizes(SurfaceTexture.class);
if (outputSizes == null || outputSizes.length == 0) {
throw new IllegalStateException(
"Camera " + cameraId + "doesn't support any outputSize.");
}
Size chosen = outputSizes[0];
for (Size s : outputSizes) {
if (chosen.getWidth() >= s.getWidth() && chosen.getHeight() >= s.getHeight()) {
chosen = s;
}
}
return chosen;
}
private void postUpdateFlashlight() {
ensureHandler();
mHandler.post(mUpdateFlashlightRunnable);
}
private String getCameraId() throws CameraAccessException {
String[] ids = mCameraManager.getCameraIdList();
for (String id : ids) {
CameraCharacteristics c = mCameraManager.getCameraCharacteristics(id);
Boolean flashAvailable = c.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);
Integer lensFacing = c.get(CameraCharacteristics.LENS_FACING);
if (flashAvailable != null && flashAvailable
&& lensFacing != null && lensFacing == CameraCharacteristics.LENS_FACING_BACK) {
return id;
}
}
return null;
}
private void updateFlashlight(boolean forceDisable) {
try {
boolean enabled;
synchronized (this) {
enabled = mFlashlightEnabled && !forceDisable;
}
if (enabled) {
if (mCameraDevice == null) {
startDevice();
return;
}
if (mSession == null) {
startSession();
return;
}
if (mFlashlightRequest == null) {
CaptureRequest.Builder builder = mCameraDevice.createCaptureRequest(
CameraDevice.TEMPLATE_PREVIEW);
builder.set(CaptureRequest.FLASH_MODE, CameraMetadata.FLASH_MODE_TORCH);
builder.addTarget(mSurface);
CaptureRequest request = builder.build();
mSession.capture(request, null, mHandler);
mFlashlightRequest = request;
}
} else {
if (mCameraDevice != null) {
mCameraDevice.close();
teardown();
}
}
} catch (Exception e) {
LogUtil.e(TAG, "Error in updateFlashlight", e);
handleError();
}
}
private void teardown() {
mCameraDevice = null;
mSession = null;
mFlashlightRequest = null;
if (mSurface != null) {
mSurface.release();
mSurfaceTexture.release();
}
mSurface = null;
mSurfaceTexture = null;
}
private void handleError() {
synchronized (this) {
mFlashlightEnabled = false;
}
dispatchError();
dispatchOff();
updateFlashlight(true);
}
private void dispatchOff() {
dispatchListeners(DISPATCH_OFF, false);
}
private void dispatchError() {
dispatchListeners(DISPATCH_ERROR, false);
}
private void dispatchAvailabilityChanged(boolean available) {
dispatchListeners(DISPATCH_AVAILABILITY_CHANGED, available);
}
private void dispatchListeners(int message, boolean argument) {
synchronized (mListeners) {
final int N = mListeners.size();
boolean cleanup = false;
for (int i = 0; i < N; i++) {
FlashlightListener l = mListeners.get(i);
if (l != null) {
if (message == DISPATCH_ERROR) {
l.onFlashlightError();
} else if (message == DISPATCH_OFF) {
l.onFlashlightOff();
} else if (message == DISPATCH_AVAILABILITY_CHANGED) {
l.onFlashlightAvailabilityChanged(argument);
}
} else {
cleanup = true;
}
}
if (cleanup) {
cleanUpListenersLocked(null);
}
}
}
private void cleanUpListenersLocked(FlashlightListener listener) {
for (int i = mListeners.size() - 1; i >= 0; i--) {
FlashlightListener found = mListeners.get(i);
if (found == null || found == listener) {
mListeners.remove(i);
}
}
}
private final Runnable mUpdateFlashlightRunnable = new Runnable() {
@Override
public void run() {
updateFlashlight(false);
}
};
private final Runnable mKillFlashlightRunnable = new Runnable() {
@Override
public void run() {
synchronized (this) {
mFlashlightEnabled = false;
}
updateFlashlight(true);
dispatchOff();
}
};
private final CameraManager.AvailabilityCallback mAvailabilityCallback =
new CameraManager.AvailabilityCallback() {
@Override
public void onCameraAvailable(String cameraId) {
if (DEBUG) LogUtil.d(TAG, "onCameraAvailable(" + cameraId + ")");
if (cameraId.equals(mCameraId)) {
setCameraAvailable(true);
}
}
@Override
public void onCameraUnavailable(String cameraId) {
if (DEBUG) LogUtil.d(TAG, "onCameraUnavailable(" + cameraId + ")");
if (cameraId.equals(mCameraId)) {
setCameraAvailable(false);
}
}
private void setCameraAvailable(boolean available) {
boolean changed;
synchronized (FlashlightController.this) {
changed = mCameraAvailable != available;
mCameraAvailable = available;
}
if (changed) {
if (DEBUG) LogUtil.d(TAG, "dispatchAvailabilityChanged(" + available + ")");
dispatchAvailabilityChanged(available);
}
}
};
public interface FlashlightListener {
void onFlashlightOff();
void onFlashlightError();
void onFlashlightAvailabilityChanged(boolean available);
}
}
以上是FlashlightController 类。
打开手电筒：
FlashlightController .setFlashlight(true);
关闭手电筒：
FlashlightController .killFlashlight();
仅仅是这个两个方法就可以解决问题。由于5.0系统自己实现的手电筒的功能。所以FlashlightController 这个类便是来自于5.0系统的源码。改动的地方很小。
三、
以上便可以解决手电筒的问题了。但是在实际测试过程中还是有一些问题：
1、在三星拥有5.0系统的手机上，需要用一中的方法，才可以。
2、一些手机在长时间打开手电筒后，闪光灯会自动关闭。例如魅族，Nexus。除非重启手机，否则摄像头便不好用了。