Android实现Camera2预览和拍照效果

简介

网上对于 Camera2 的介绍有很多，在 GitHub 上也有很多关于 Camera2 的封装库，但是对于那些库，封装性太强，有时候我们仅仅是需要个简简单单的拍照功能而已，因此，自定义一个 Camera 使之变得轻量级那是非常重要的了。(本文并非重复造轮子, 而是在于学习 Camera2api 的基本功能, 笔记之。)

学习要点:

使用 Android Camera2 API 的基本功能。
迭代连接到设备的所有相机的特征。
显示相机预览和拍摄照片。

Camera2 API 为连接到 Android 设备的各个相机设备提供了一个界面。 它替代了已弃用的 Camera 类。

• 使用 getCameraidList 获取所有可用摄像机的列表。 然后，您可以使用 getCameraCharacteristics，并找到适合您需要的最佳相机（前 / 后面，分辨率等）。
• 创建一个 CameraDevice.StateCallback 的实例并打开相机。 当相机打开时，准备开始相机预览。
• 使用 TextureView 显示相机预览。 创建一个 CameraCaptureSession 并设置一个重复的 CaptureRequest。
• 静像拍摄需要几个步骤。 首先，需要通过更新相机预览的 CaptureRequest 来锁定相机的焦点。
• 然后，以类似的方式，需要运行一个预捕获序列。之后，它准备拍摄一张照片。 创建一个新的 CaptureRequest 并调用 [capture] 。
  

完成后，别忘了解锁焦点。

实现效果

环境

SDK>21

Camera2 类图

代码实现

CameraPreview.java

public class CameraPreview extends TextureView {  private static final String TAG = "CameraPreview";  private static final SparseIntArray ORIENTATIONS = new SparseIntArray();//从屏幕旋转转换为JPEG方向  private static final int MAX_PREVIEW_WIDTH = 1920;//Camera2 API 保证的最大预览宽高  private static final int MAX_PREVIEW_HEIGHT = 1080;  private static final int STATE_PREVIEW = 0;//显示相机预览  private static final int STATE_WAITING_LOCK = 1;//焦点锁定中  private static final int STATE_WAITING_PRE_CAPTURE = 2;//拍照中  private static final int STATE_WAITING_NON_PRE_CAPTURE = 3;//其它状态  private static final int STATE_PICTURE_TAKEN = 4;//拍照完毕  private int mState = STATE_PREVIEW;  private int mRatioWidth = 0, mRatioHeight = 0;  private int mSensorOrientation;  private boolean mFlashSupported;  private Semaphore mCameraopenCloseLock = new Semaphore(1);//使用信号量 Semaphore 进行多线程任务调度  private Activity activity;  private File mFile;  private HandlerThread mBackgroundThread;  private Handler mBackgroundHandler;  private Size mPreviewSize;  private String mCameraId;  private CameraDevice mCameraDevice;  private CaptureRequest.Builder mPreviewRequestBuilder;  private CaptureRequest mPreviewRequest;  private CameraCaptureSession mCaptureSession;  private ImageReader mImageReader;  static {    ORIENTATIONS.append(Surface.ROTATION_0, 90);    ORIENTATIONS.append(Surface.ROTATION_90, 0);    ORIENTATIONS.append(Surface.ROTATION_180, 270);    ORIENTATIONS.append(Surface.ROTATION_270, 180);  }  public CameraPreview(Context context) {    this(context, null);  }  public CameraPreview(Context context, AttributeSet attrs) {    this(context, attrs, 0);  }  public CameraPreview(Context context, AttributeSet attrs, int defStyleAttr) {    super(context, attrs, defStyleAttr);    mFile = new File(getContext().getExternalFilesDir(null), "pic.jpg");  }  @Override  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {    super.onMeasure(widthMeasureSpec, heightMeasureSpec);    int width = MeasureSpec.getSize(widthMeasureSpec);    int height = MeasureSpec.getSize(heightMeasureSpec);    if (0 == mRatioWidth || 0 == mRatioHeight) {      setMeasuredDimension(width, height);    } else {      if (width < height * mRatioWidth / mRatioHeight) {        setMeasuredDimension(width, width * mRatioHeight / mRatioWidth);      } else {        setMeasuredDimension(height * mRatioWidth / mRatioHeight, height);      }    }  }  public void onResume(Activity activity) {    this.activity = activity;    startBackgroundThread();    //当Activity或Fragment OnResume()时,可以冲洗打开一个相机并开始预览,否则,这个Surface已经准备就绪    if (this.isAvailable()) {      openCamera(this.getWidth(), this.getHeight());    } else {      this.setSurfaceTextureListener(mSurfaceTextureListener);    }  }  public void onPause() {    closeCamera();    stopBackgroundThread();  }  public void setOutPutDir(File file) {    this.mFile = file;  }  public void setAspectRatio(int width, int height) {    if (width < 0 || height < 0) {      throw new IllegalArgumentException("Size can't be negative");    }    mRatioWidth = width;    mRatioHeight = height;    requestLayout();  }  public void setAutoFlash(CaptureRequest.Builder requestBuilder) {    if (mFlashSupported) {      requestBuilder.set(CaptureRequest.CONTROL_AE_MODE,          CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);    }  }  public void takePicture() {    lockFocus();  }  private void startBackgroundThread() {    mBackgroundThread = new HandlerThread("CameraBackground");    mBackgroundThread.start();    mBackgroundHandler = new Handler(mBackgroundThread.getLooper());  }  private void stopBackgroundThread() {    mBackgroundThread.quitSafely();    try {      mBackgroundThread.join();      mBackgroundThread = null;      mBackgroundHandler = null;    } catch (InterruptedException e) {      e.printStackTrace();    }  }    private final TextureView.SurfaceTextureListener mSurfaceTextureListener = new TextureView.SurfaceTextureListener() {    @Override    public void onSurfaceTextureAvailable(SurfaceTexture texture, int width, int height) {      openCamera(width, height);    }    @Override    public void onSurfaceTextureSizeChanged(SurfaceTexture texture, int width, int height) {      configureTransfORM(width, height);    }    @Override    public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {      return true;    }    @Override    public void onSurfaceTextureUpdated(SurfaceTexture texture) {    }  };    private final CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {    @Override    public void onOpened(@NonNull CameraDevice cameraDevice) {      mCameraOpenCloseLock.release();      Log.d(TAG, "相机已打开");      mCameraDevice = cameraDevice;      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;      if (null != activity) {        activity.finish();      }    }  };    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_PRE_CAPTURE: {          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_PRE_CAPTURE;          }          break;        }        case STATE_WAITING_NON_PRE_CAPTURE: {          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);    }  };    private void configureTransform(int viewWidth, int viewHeight) {    if (null == mPreviewSize || null == activity) {      return;    }    int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();    Matrix matrix = new Matrix();    RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);    RectF bufferRect = new RectF(0, 0, mPreviewSize.getHeight(), mPreviewSize.getWidth());    float centerX = viewRect.centerX();    float centerY = viewRect.centerY();    if (Surface.ROTATION_90 == rotation || Surface.ROTATION_270 == rotation) {      bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());      matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);      float scale = Math.max(          (float) viewHeight / mPreviewSize.getHeight(),          (float) viewWidth / mPreviewSize.getWidth());      matrix.postScale(scale, scale, centerX, centerY);      matrix.postRotate(90 * (rotation - 2), centerX, centerY);    } else if (Surface.ROTATION_180 == rotation) {      matrix.postRotate(180, centerX, centerY);    }    this.setTransform(matrix);  }    private void openCamera(int width, int height) {    setUpCameraOutputs(width, height);    configureTransform(width, height);    CameraManager manager = (CameraManager) getContext().getSystemService(Context.CAMERA_SERVICE);    try {      if (!mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {        throw new RuntimeException("Time out waiting to lock camera opening.");      }      if (ActivityCompat.checkSelfPermission(activity, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {        // TODO: Consider calling        //  ActivityCompat#requestPermissions        // here to request the missing permissions, and then overriding        //  public void onRequestPermissionsResult(int requestCode, String[] permissions,        //                     int[] grantResults)        // to handle the case where the user grants the permission. See the documentation        // for ActivityCompat#requestPermissions for more details.        return;      }      manager.openCamera(mCameraId, mStateCallback, mBackgroundHandler);    } catch (CameraAccessException e) {      e.printStackTrace();    } catch (InterruptedException e) {      throw new RuntimeException("Interrupted while trying to lock camera opening.", e);    }  }    private void closeCamera() {    try {      mCameraOpenCloseLock.acquire();      if (null != mCaptureSession) {        mCaptureSession.close();        mCaptureSession = null;      }      if (null != mCameraDevice) {        mCameraDevice.close();        mCameraDevice = null;      }      if (null != mImageReader) {        mImageReader.close();        mImageReader = null;      }    } catch (InterruptedException e) {      throw new RuntimeException("Interrupted while trying to lock camera closing.", e);    } finally {      mCameraOpenCloseLock.release();    }  }    @SuppressWarnings("SuspiciousNameCombination")  private void setUpCameraOutputs(int width, int height) {    CameraManager manager = (CameraManager) getContext().getSystemService(Context.CAMERA_SERVICE);    try {      for (String cameraId : manager.getCameraIdList()) {        CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);        // 在这个例子中不使用前置摄像头        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;        }        Size largest = Collections.max(Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)),            new CompareSizesByArea());        mImageReader = ImageReader.newInstance(largest.getWidth(), largest.getHeight(),            ImageFormat.JPEG, 2);        mImageReader.setOnImageAvailableListener(            mOnImageAvailableListener, mBackgroundHandler);        int displayRotation = activity.getWindowManager().getDefaultDisplay().getRotation();        // noinspection ConstantConditions        mSensorOrientation = characteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);        boolean swappedDimensions = false;        switch (displayRotation) {          case Surface.ROTATION_0:          case Surface.ROTATION_180:            if (mSensorOrientation == 90 || mSensorOrientation == 270) {              swappedDimensions = true;            }            break;          case Surface.ROTATION_90:          case Surface.ROTATION_270:            if (mSensorOrientation == 0 || mSensorOrientation == 180) {              swappedDimensions = true;            }            break;          default:            Log.e(TAG, "Display rotation is invalid: " + displayRotation);        }        Point displaySize = new Point();        activity.getWindowManager().getDefaultDisplay().getSize(displaySize);        int rotatedPreviewWidth = width;        int rotatedPreviewHeight = height;        int maxPreviewWidth = displaySize.x;        int maxPreviewHeight = displaySize.y;        if (swappedDimensions) {          rotatedPreviewWidth = height;          rotatedPreviewHeight = width;          maxPreviewWidth = displaySize.y;          maxPreviewHeight = displaySize.x;        }        if (maxPreviewWidth > MAX_PREVIEW_WIDTH) {          maxPreviewWidth = MAX_PREVIEW_WIDTH;        }        if (maxPreviewHeight > MAX_PREVIEW_HEIGHT) {          maxPreviewHeight = MAX_PREVIEW_HEIGHT;        }        mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class),            rotatedPreviewWidth, rotatedPreviewHeight, maxPreviewWidth,            maxPreviewHeight, largest);        int orientation = getResources().getConfiguration().orientation;        if (orientation == Configuration.ORIENTATION_LANDSCAPE) {          setAspectRatio(mPreviewSize.getWidth(), mPreviewSize.getHeight());        } else {          setAspectRatio(mPreviewSize.getHeight(), mPreviewSize.getWidth());        }        Boolean available = characteristics.get(CameraCharacteristics.FLASH_INFO_AVAILABLE);        mFlashSupported = available == null ? false : available;        mCameraId = cameraId;        return;      }    } catch (CameraAccessException e) {      e.printStackTrace();    } catch (NullPointerException e) {      Log.e(TAG, "设备不支持Camera2");    }  }    private static Size chooseOptimalSize(Size[] choices, int textureViewWidth, int textureViewHeight,                     int maxWidth, int maxHeight, Size aspectRatio) {    List<Size> bigEnough = new ArrayList<>();    List<Size> notBigEnough = new ArrayList<>();    int w = aspectRatio.getWidth();    int h = aspectRatio.getHeight();    for (Size option : choices) {      if (option.getWidth() <= maxWidth && option.getHeight() <= maxHeight &&          option.getHeight() == option.getWidth() * h / w) {        if (option.getWidth() >= textureViewWidth &&            option.getHeight() >= textureViewHeight) {          bigEnough.add(option);        } else {          notBigEnough.add(option);        }      }    }    if (bigEnough.size() > 0) {      return Collections.min(bigEnough, new CompareSizesByArea());    } else if (notBigEnough.size() > 0) {      return Collections.max(notBigEnough, new CompareSizesByArea());    } else {      Log.e(TAG, "Couldn't find any suitable preview size");      return choices[0];    }  }    private void createCameraPreviewSession() {    try {      SurfaceTexture texture = this.getSurfaceTexture();      assert texture != null;      // 将默认缓冲区的大小配置为想要的相机预览的大小      texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());      Surface surface = new Surface(texture);      mPreviewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);      mPreviewRequestBuilder.addTarget(surface);      // 我们创建一个 CameraCaptureSession 来进行相机预览      mCameraDevice.createCaptureSession(Arrays.asList(surface, mImageReader.getSurface()),          new CameraCaptureSession.StateCallback() {            @Override            public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {              if (null == mCameraDevice) {                return;              }              // 会话准备好后，我们开始显示预览              mCaptureSession = cameraCaptureSession;              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 cameraCaptureSession) {            }          }, null);    } catch (CameraAccessException e) {      e.printStackTrace();    }  }    private int getOrientation(int rotation) {    return (ORIENTATIONS.get(rotation) + mSensorOrientation + 270) % 360;  }    private void lockFocus() {    try {      // 如何通知相机锁定焦点      mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);      // 通知mCaptureCallback等待锁定      mState = STATE_WAITING_LOCK;      mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback, mBackgroundHandler);    } catch (CameraAccessException e) {      e.printStackTrace();    }  }    private void unlockFocus() {    try {      mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER,          CameraMetadata.CONTROL_AF_TRIGGER_CANCEL);      setAutoFlash(mPreviewRequestBuilder);      mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback,          mBackgroundHandler);      mState = STATE_PREVIEW;      mCaptureSession.setRepeatingRequest(mPreviewRequest, mCaptureCallback,          mBackgroundHandler);    } catch (CameraAccessException e) {      e.printStackTrace();    }  }    private void captureStillPicture() {    try {      if (null == activity || null == mCameraDevice) {        return;      }      final CaptureRequest.Builder captureBuilder =          mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);      captureBuilder.addTarget(mImageReader.getSurface());      captureBuilder.set(CaptureRequest.CONTROL_AF_MODE,          CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);      setAutoFlash(captureBuilder);      // 方向      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) {          Toast.makeText(getContext(), "Saved: " + mFile, Toast.LENGTH_SHORT).show();          Log.d(TAG, mFile.toString());          unlockFocus();        }      };      mCaptureSession.stopRepeating();      mCaptureSession.abortCaptures();      mCaptureSession.capture(captureBuilder.build(), captureCallback, null);    } catch (CameraAccessException e) {      e.printStackTrace();    }  }    private void runPreCaptureSequence() {    try {      // 设置拍照参数请求      mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER,          CaptureRequest.CONTROL_AE_PRECAPTURE_TRIGGER_START);      mState = STATE_WAITING_PRE_CAPTURE;      mCaptureSession.capture(mPreviewRequestBuilder.build(), mCaptureCallback, mBackgroundHandler);    } catch (CameraAccessException e) {      e.printStackTrace();    }  }    private static class CompareSizesByArea implements Comparator<Size> {    @Override    public int compare(Size lhs, Size rhs) {      return Long.signum((long) lhs.getWidth() * lhs.getHeight() -          (long) rhs.getWidth() * rhs.getHeight());    }  }    private final ImageReader.OnImageAvailableListener mOnImageAvailableListener      = new ImageReader.OnImageAvailableListener() {    @Override    public void onImageAvailable(ImageReader reader) {      mBackgroundHandler.post(new ImageSaver(reader.acquireNextImage(), mFile));    }  };    private static class ImageSaver implements Runnable {    private final Image mImage;    private final File mFile;    ImageSaver(Image image, File file) {      mImage = image;      mFile = file;    }    @Override    public void run() {      ByteBuffer buffer = mImage.getPlanes()[0].getBuffer();      byte[] bytes = new byte[buffer.remaining()];      buffer.get(bytes);      FileOutputStream output = null;      try {        output = new FileOutputStream(mFile);        output.write(bytes);      } catch (IOException e) {        e.printStackTrace();      } finally {        mImage.close();        if (null != output) {          try {            output.close();          } catch (IOException e) {            e.printStackTrace();          }        }      }    }  }}