基础概念
Camera2是Android5.0推出的新的相机api（在5.0以下系统没法使用）。它采用管道式的设计，支持单个或者顺序执行的多个请求。
与Camera1的区别：
Camera2采用CameraManager来管理，而不是像camera1一样返回camera对象让我们进行操作。camera2的预览，拍照都是请求一次会话（管道的输入然后输出）。
新增了许多camera1不具备的功能，如对焦模式，曝光模式，快门，还有输出原始照片数据（RAW）等
基本用法
- 创建TextureView，加入TextureView状态回调
- TextureView回调成功，获取CameraManager对象，打开连接camera，并加入camera调用回调方法
- camera连接回调成功，创建相机会话对象，并加入相机会话的回调方法
- 在相机会话的回调方法中处理拍照生成图片等操作
接下来我们会一步步用真实的代码去讲解每一步操作
第一步：创建TextureView，并加入TextureView的回调
/**
* 创建textureview回调方法
**/
private final TextureView.SurfaceTextureListener mSurfaceTextureListener = new TextureView.SurfaceTextureListener() {
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
openCamera(width, height);
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
configureTransform(width, height);
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
return false;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture surface) {
}
};
第二步：在onSurfaceTextureAvailable() 中去创建CameraDevice对象来连接Camera。当然其中要设置一些参数来配置我们需要的Camera。比如正反摄像头，自动对焦等。
private void openCamera(int width, int height) {
setUpCameraOutputs(width, height); // 该方法用于在系统返回的CameraId列表（不同分辨率，正反镜头等）获取最适合的CameraId
configureTransform(width, height); // 根据返回的镜头去调整TextureView的大小
CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
try {
if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
throw new RuntimeException("Time out waitting to lock camera opening");
}
manager.openCamera(mCameraId, mStateCallback, mBackgroundHandler); // mStateCallback的代码在下面
} catch (CameraAccessException e) {
e.printStackTrace();
} catch (InterruptedException e) {
throw new RuntimeException("Interrupted while trying to lock camera opening.", e);
}
}
提前创建好的相机状态回调
private final CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {
@Override
public void onOpened(@NonNull CameraDevice camera) {
mCameraOpenCloseLock.release();
mCameraDevice = camera;
createCameraPreviewSession();
}
@Override
public void onDisconnected(@NonNull CameraDevice camera) {
}
@Override
public void onError(@NonNull CameraDevice camera, int error) {
}
};
第三步：camera连接回调成功，创建相机会话对象
private void createCameraPreviewSession() {
try {
SurfaceTexture texture = mTextureView.getSurfaceTexture();
assert texture != null;
texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
Surface surface = new Surface(texture);
mPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
mPreviewRequestBuilder.addTarget(surface);
mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),
new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(@NonNull CameraCaptureSession session) {
if (mCameraDevice == null) {
return;
}
mCaptureSession = session;
try {
mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE,
CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
setAutoFlash(mPreviewRequestBuilder);
mPreviewRequest = mPreviewRequestBuilder.build();
mCaptureSession.setRepeatingRequest(mPreviewRequest,
mCaptureCallback, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(@NonNull CameraCaptureSession session) {
}
}, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
第四步：最后看下相机会话的回调处理方法，用于处理拍照生成图片等操作
private CameraCaptureSession.CaptureCallback mCaptureCallback =
new CameraCaptureSession.CaptureCallback() {
private void process(CaptureResult result) {
switch (mState) {
case STATE_PREVIEW: {
break;
}
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) {
Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
if (aeState == null || aeState == CaptureResult.CONTROL_AE_STATE_CONVERGED) {
mState = STATE_PICTURE_TAKEN;
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;
}
}
}
@Override
public void onCaptureProgressed(@NonNull CameraCaptureSession session, @NonNull CaptureRequest request, @NonNull CaptureResult partialResult) {
process(partialResult);
}
@Override
public void onCaptureCompleted(@NonNull CameraCaptureSession session, @NonNull CaptureRequest request, @NonNull TotalCaptureResult result) {
process(result);
}
};
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