Android Camera2

Android 5 (API 21, L) 新增加了Camera2，和之前的Camera使用起來較複雜，但是多了許多功能，支援RAW輸出、調整對焦模式、曝光模式等。

Camera2

首先先了解幾個重要的Class

• CameraManager : 管理攝影設備，主要功用是獲取所有攝影設備和打開指定的攝影鏡頭。
• CameraDevice : 攝影設備，可透過CameraManager.openCamera()來取得。
• CameraCaptureSession : 用於處理拍照及預覽工作。
• CaptureRequest ：捕捉畫面請求，用來定義輸出緩衝區及顯示 (TextureView or SurfaceView)

我們在畫面中加入一個TextureView，用來預覽攝影鏡頭目前捕捉到的畫面。
並設定Listener監聽TextureView是否已設置好。

程式參數

MainActivity.java

private TextureView mTextureView;
private Size mPreviewSize;

private CameraDevice mCameraDevice;
private String mCameraId;

private ImageReader mImageReader;
private CaptureRequest.Builder mCaptureRequestBuilder;
private CaptureRequest mCaptureRequest;
private CameraCaptureSession mPreviewSession;

private static String[] PERMISSIONS_STORAGE = {
     Manifest.permission.READ_EXTERNAL_STORAGE,
     Manifest.permission.WRITE_EXTERNAL_STORAGE,
     Manifest.permission.CAMERA
};

private static final int RC_HANDLE_CAMERA_PERM = 2;

MainActivity: onCreate

mTextureView = findViewById(R.id.textureView);
mTextureView.setSurfaceTextureListener(textureListener);

當TextureView設置好之後，再來設置並打開攝影鏡頭。

MainActivity.java

TextureView.SurfaceTextureListener textureListener = new TextureView.SurfaceTextureListener() {
    @Override
    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
        //設置攝影鏡頭
        setupCamera(width, height);
        //打開攝影鏡頭。
        openCamera();
    }
};

利用CamaraManager取得所有攝影鏡頭的資訊，此例子使用後置鏡頭，我們可根據CameraCharacteristics屬性略過前置鏡頭並開啟後置鏡頭。

由於攝影鏡頭支援眾多格式和大小，可由StreamConfigurationMap取得這些屬性。根據TextureView的長寬，設定攝影鏡頭的格式與大小。

MainActivity.java

private void setupCamera(int width, int height) {
    CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
    try {
        //獲取所有攝影設備
        String[] cameraList = manager.getCameraIdList();
        for (String cameraId: cameraList) {
            //取得攝影設備屬性
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
            //不擷取前置鏡頭的畫面
            if (characteristics.get(CameraCharacteristics.LENS_FACING) == CameraCharacteristics.LENS_FACING_FRONT)
                continue;
            //取得StreamConfigurationMap，取得攝影鏡頭支持的所有輸出格式和尺寸
            StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            //根據TextureView的尺寸設置預覽尺寸
            mPreviewSize = getOptimalSize(map.getOutputSizes(SurfaceTexture.class), width, height);
            mCameraId = cameraId;
            break;
        }
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

MainActivity.java

//選擇sizeMap中最接近width和height的尺寸
private Size getOptimalSize(Size[] sizeMap, int width, int height) {
    List<Size> sizeList = new ArrayList<>();
    for (Size option : sizeMap) {
         if (width > height) {
             if (option.getWidth() > width && option.getHeight() > height) {
                sizeList.add(option);
	     }
        } else {
            if (option.getWidth() > height && option.getHeight() > width) {
                sizeList.add(option);
            }
        }
    }
    if (sizeList.size() > 0) {
         return Collections.min(sizeList, new Comparator<Size>() {
             @Override
             public int compare(Size lhs, Size rhs) {
                 return Long.signum(lhs.getWidth() * lhs.getHeight() - rhs.getWidth() * rhs.getHeight());
             }
         });
    }
    return sizeMap[0];
}

根據mCameraId來決定要開啟的鏡頭，並設置CameraDevice.StateCallback監聽狀態。

MainActivity.java

private void openCamera() {
    CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
    try {
        //檢查權限
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
             //請求權限
             ActivityCompat.requestPermissions(this, PERMISSIONS_STORAGE, RC_HANDLE_CAMERA_PERM);
             return;
        }
        //根據mCameraId來決定要開啟的鏡頭
        manager.openCamera(mCameraId, mStateCallback, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

MainActivity.java

private final CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {
    @Override
    public void onOpened(CameraDevice camera) {
        mCameraDevice = camera;
        //預覽畫面
        startPreview();
    }
	
    @Override
    public void onDisconnected(@NonNull CameraDevice camera) {
        Log.e(TAG, "onDisconnected");
    }
	
    @Override
    public void onError(@NonNull CameraDevice camera, int error) {
        Log.e(TAG, "onError: " + error);
    }
};

設置預覽畫面，將捕捉到的畫面顯示於TextureView中。

MainActivity.java

private void startPreview() {
    SurfaceTexture mSurfaceTexture = mTextureView.getSurfaceTexture();
    //設置TextureView的緩衝區大小
    mSurfaceTexture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
    //獲取Surface顯示預覽數據
    Surface mSurface = new Surface(mSurfaceTexture);
    try {
        //創建預覽請求CaptureRequestBuilder，TEMPLATE_PREVIEW
        mCaptureRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
        //設置Surface作為預覽顯示界面
        mCaptureRequestBuilder.addTarget(mSurface);
        //創建捕捉畫面，並設置callback
        mCameraDevice.createCaptureSession(Arrays.asList(mSurface),mCaptureCallback, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

當預覽請求設置好之後，設定Repeat，讓畫面持續更新。

MainActivity.java

private final CameraCaptureSession.StateCallback mCaptureCallback  = new CameraCaptureSession.StateCallback() {
    @Override
    public void onConfigured(CameraCaptureSession session) {
        try {
            //創建捕獲請求
            mCaptureRequest = mCaptureRequestBuilder.build();
            mPreviewSession = session;
            //設置反覆捕獲數據，持續畫面更新
            mPreviewSession.setRepeatingRequest(mCaptureRequest, null, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
}
	
    @Override
    public void onConfigureFailed(CameraCaptureSession session) {
	
    }
};

執行結果