android-Camera2Basic 解析
1.Android Camera2介绍
Android 5.0(API Level 21) 重新设计了 Camera，废弃了之前的 Camera，改用现在的 Camera2 API，在Camera2上引入了Session/Request的概念，使用的复杂度远超之前的 Camera。
1.1 Camera2主要类简介
- CameraManager：摄像头管理类，用于检测，打开系统摄像头，可以通过
getCameraCharacteristics(cameraId)获取摄像头的特征 - CameraCharacteristics：相机的特性类，可以得到相机是否支持自动对焦，是否支持闪光灯等特征
- CameraDevice：相机设备类
- CameraCaptureSession：用于创建预览，拍照的Session类。
- CaptureRequest：相机的请求类，可以通过这个类获取一次捕获的请求，可以设置一些参数等。
- CameraRequest和CameraRequest.Builder：当程序调用
setRepeatingRequest()方法进行预览时，或调用capture()方法进行拍照时，都需要传入CameraRequest参数。CameraRequest代表了一次捕获请求，用于描述捕获图片的各种参数设置，比如对焦模式、曝光模式……总之，程序需要对照片所做的各种控制，都通过CameraRequest参数进行设置。CameraRequest.Builder则负责生成CameraRequest对象。
1.2 Camera2 API 基本架构
-
APP通过创建一个CaptureRequest向CameraDevice发起Capture请求
-
CameraDevice收到请求后返回对应数据的预览数据
-
点击拍照后，会从ImageReader中读取数据
-
CaptureRequest代表请求控制的Camera参数, CameraMetadata(CaptureResult)则表示当前返回帧中Camera使用的参数以及当前状态.
1.3 使用流程
-
初始化，打开Camera
- 通过
if (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) { requestCameraPermission(); return; }获取权限
-
通过
context.getSystemService(Context.CAMERA_SERVICE)获取CameraManager -
通过
CameraManager.getCameraCharacteristics(cameraId)获取相机的摄像头的特性SENSOR_ORIENTATION：获取摄像头的拍照的方向LENS_FACING：获取摄像头的方向。LENS_FACING_FRONT是前摄像头，LENS_FACING_BACK是后摄像头。- 获取FPS的范围
- 获取大小
-
调用
CameraManager .open()方法在回调中得到CameraDevice.
-
Create Session
通过CameraDevice.createCaptureSession()在回调中获取CameraCaptureSession. -
Config Session
构建CaptureRequest, 有三种模式可选 预览/拍照/录像. -
Capture
拍照数据可以在ImageReader.OnImageAvailableListener回调中获取,CaptureCallback中则可获取拍照实际的参数和Camera当前状态.
2.android-Camera2Basic介绍
android-Camera2Basic是谷歌官方给的Camera2的demo，演示了Camrea2 API的基本功能，通过这个Demo，我们可以掌握连接设备，显示预览，以及拍照的基本使用。
2.1 项目结构
├── .DS_Store
└── camera2basic
├── AutoFitTextureView.java
├── Camera2BasicFragment.java
└── CameraActivity.java
2.2 代码详解
2.2.1 打开相机，创建预览
2.2.1.1 openCamera
private void openCamera(int width, int height) {
if (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED) {
//请求权限
requestCameraPermission();
return;
}
//设置相机相关的参数
setUpCameraOutputs(width, height);
configureTransform(width, height);
Activity activity = getActivity();
CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
try {
if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
throw new RuntimeException("Time out waiting to lock camera opening.");
}
manager.openCamera(mCameraId, mStateCallback, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
} catch (InterruptedException e) {
throw new RuntimeException("Interrupted while trying to lock camera opening.", e);
}
}
2.2.1.1.1 setUpCameraOutputs(width, height);
@SuppressWarnings("SuspiciousNameCombination")
private void setUpCameraOutputs(int width, int height) {
Activity activity = getActivity();
CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
try {
//获取摄像头可用列表
for (String cameraId : manager.getCameraIdList()) {
//获取相机的特性
CameraCharacteristics characteristics
= manager.getCameraCharacteristics(cameraId);
// 不使用前置摄像头
Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);
if (facing != null && facing == CameraCharacteristics.LENS_FACING_FRONT) {
continue;
}
StreamConfigurationMap map = characteristics.get(
CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
if (map == null) {
continue;
}
// For still image captures, we use the largest available size.
Size largest = Collections.max(
Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),
new CompareSizesByArea());
//设置ImageReader接收的图片格式，以及允许接收的最大图片数目
mImageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),
ImageFormat.JPEG, /*maxImages*/2);
//设置图片存储的监听
mImageReader.setOnImageAvailableListener(
mOnImageAvailableListener, mBackgroundHandler);
...
}
2.2.1.2 CameraDevice.StateCallback监听
private final CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {
@Override
public void onOpened(@NonNull CameraDevice cameraDevice) {
// This method is called when the camera is opened. We start camera preview here.
mCameraOpenCloseLock.release();
mCameraDevice = cameraDevice;
//创建PreviewSession
createCameraPreviewSession();
}
@Override
public void onDisconnected(@NonNull CameraDevice cameraDevice) {
mCameraOpenCloseLock.release();
cameraDevice.close();
mCameraDevice = null;
}
@Override
public void onError(@NonNull CameraDevice cameraDevice, int error) {
mCameraOpenCloseLock.release();
cameraDevice.close();
mCameraDevice = null;
Activity activity = getActivity();
if (null != activity) {
activity.finish();
}
}
};
2.2.1.3 createCaptureSession
private void createCameraPreviewSession() {
try {
SurfaceTexture texture = mTextureView.getSurfaceTexture();
assert texture != null;
// We configure the size of default buffer to be the size of camera preview we want.
texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
// This is the output Surface we need to start preview.
Surface surface = new Surface(texture);
// We set up a CaptureRequest.Builder with the output Surface.
mPreviewRequestBuilder
= mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
mPreviewRequestBuilder.addTarget(surface);
// Here, we create a CameraCaptureSession for camera preview.
mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
// The camera is already closed
if (null == mCameraDevice) {
return;
}
// When the session is ready, we start displaying the preview.
mCaptureSession = cameraCaptureSession;
try {
// Auto focus should be continuous for camera preview.
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
// Flash is automatically enabled when necessary.
setAutoFlash(mPreviewRequestBuilder);
// Finally, we start displaying the camera preview.
mPreviewRequest = mPreviewRequestBuilder.build();
mCaptureSession.setRepeatingRequest(mPreviewRequest,
mCaptureCallback, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(
@NonNull CameraCaptureSession cameraCaptureSession) {
showToast("Failed");
}
}, null
);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
项目中有注释，不做过多说明
2.2.2 拍照
拍照的过程就是我们向已经打开好的相机获取静态预览帧的过程。
2.2.2.1 对焦
private void lockFocus() {
try {
// This is how to tell the camera to lock focus.
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,
CameraMetadata.CONTROL_AF_TRIGGER_START);
// Tell #mCaptureCallback to wait for the lock.
mState = STATE_WAITING_LOCK;
mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback,
mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
向CameraCaptureSession发送对焦请求，并且对对焦是否成功进行监听，在mCaptureCallback中对回调进行处理。
private CameraCaptureSession.CaptureCallback mCaptureCallback
= new CameraCaptureSession.CaptureCallback() {
private void process(CaptureResult result) {
switch (mState) {
case STATE_PREVIEW: {
// We have nothing to do when the camera preview is working normally.
break;
}
//等待对焦
case STATE_WAITING_LOCK: {
Integer afState = result.get(CaptureResult.CONTROL_AF_STATE);
if (afState == null) {
captureStillPicture();
} else if (CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED == afState ||
CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED == afState) {
// CONTROL_AE_STATE can be null on some devices
Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
if (aeState == null ||
aeState == CaptureResult.CONTROL_AE_STATE_CONVERGED) {
mState = STATE_PICTURE_TAKEN;
//对焦完成
captureStillPicture();
} else {
runPrecaptureSequence();
}
}
break;
}
case STATE_WAITING_PRECAPTURE: {
// CONTROL_AE_STATE can be null on some devices
Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
if (aeState == null ||
aeState == CaptureResult.CONTROL_AE_STATE_PRECAPTURE ||
aeState == CaptureRequest.CONTROL_AE_STATE_FLASH_REQUIRED) {
mState = STATE_WAITING_NON_PRECAPTURE;
}
break;
}
case STATE_WAITING_NON_PRECAPTURE: {
// CONTROL_AE_STATE can be null on some devices
Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
if (aeState == null || aeState != CaptureResult.CONTROL_AE_STATE_PRECAPTURE) {
mState = STATE_PICTURE_TAKEN;
captureStillPicture();
}
break;
}
}
}
2.2.2.2 拍摄图片
private void captureStillPicture() {
try {
final Activity activity = getActivity();
if (null == activity || null == mCameraDevice) {
return;
}
// This is the CaptureRequest.Builder that we use to take a picture.
final CaptureRequest.Builder captureBuilder =
mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
captureBuilder.addTarget(mImageReader.getSurface());
// Use the same AE and AF modes as the preview.
captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,
CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
setAutoFlash(captureBuilder);
// Orientation
int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();
captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, getOrientation(rotation));
CameraCaptureSession.CaptureCallback CaptureCallback
= new CameraCaptureSession.CaptureCallback() {
@Override
public void onCaptureCompleted(@NonNull CameraCaptureSession session,
@NonNull CaptureRequest request,
@NonNull TotalCaptureResult result) {
showToast("Saved: " + mFile);
Log.d(TAG, mFile.toString());
unlockFocus();
}
};
mCaptureSession.stopRepeating();
mCaptureSession.abortCaptures();
mCaptureSession.capture(captureBuilder.build(), CaptureCallback, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
代码中有相应的注释。
注意Demo中的onCaptureCompleted完成后，又调用unlockFocus()解锁了焦点。是因为Demo做的是连续拍照，如果实现的是只拍一张照片，需要将unlockFocus()去掉。
2.2.2.3 存图片
存图片的操作是在之前设置ImageReader的监听方法里面进行存储的。
private final ImageReader.OnImageAvailableListener mOnImageAvailableListener
= new ImageReader.OnImageAvailableListener() {
@Override
public void onImageAvailable(ImageReader reader) {
mBackgroundHandler.post(new ImageSaver(reader.acquireNextImage(), mFile));
}
};
参考资料
Android Camera2 使用总结
Android Camera2 简介