CameraService

以前在开发中遇到过一个项目，需要调用手机的拍照，并把照片传过去。但是拍照时手机不能让用户看到相机打开。

思路是启动一个service，service中实现一个surfaceview，surfaceview是一个像素的点，这样就防止了用户看到相机被打开。

先看surfaceview的实现：

private void makeAndAddSurfaceView() {
        SurfaceView dummyView = new SurfaceView(this.mApplication);
        SurfaceHolder holder = dummyView.getHolder();
        holder.addCallback(this);
        holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

        WindowManager wm = (WindowManager)this.mApplication.getSystemService(Context.WINDOW_SERVICE);

        WindowManager.LayoutParams params = new WindowManager.LayoutParams(1, 1,
                WindowManager.LayoutParams.TYPE_SYSTEM_ALERT,
                WindowManager.LayoutParams.FLAG_NOT_FOCUSABLE |
                        WindowManager.LayoutParams.FLAG_NOT_TOUCHABLE,
                PixelFormat.TRANSPARENT);
        params.gravity = Gravity.TOP | Gravity.RIGHT;
        params.alpha = PixelFormat.TRANSPARENT;
        params.x = params.y = mApplication.getResources().getDimensionPixelOffset(
                R.dimen.preview_surface_offset);

        wm.addView(dummyView, params);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
        	dummyView.setAlpha(PixelFormat.TRANSPARENT);
        }

        //dummyView.getBackground().setAlpha(PixelFormat.TRANSPARENT);
        mDummySurfaceView = dummyView;
    }

等surfaceview创建成功后，调用相机的打开，相机的打开是Camera的静态函数 Camera.open()

打开camera后，可以设置previe的fps，大小，类型等。

实现如下：

	private void startRecorder() throws IOException {
		// if (checkCameraHardware(this.mApplication)) {
		if (mCameraId < 0) {
			findFirstBackFacingCamera();
		}

		if (mCamera == null || !isStarted()) {
			try {
				mCamera = Camera.open(mCameraId);
			} catch (RuntimeException exception) {
				synchronized (cameraLock) {
					mRecordingState = CameraState.NOT_RECORDING;
					cameraLock.notifyAll();
				}
				return;
			}
		}
		// }

		if (mCamera == null) {
			return;// throw new
					// UnsupportedOperationException("No camera present");
		}

		mCamera.setPreviewDisplay(mDummySurfaceHolder);

		Camera.Parameters params = mCamera.getParameters();
		List<Size> supportSizes = mCamera.getParameters()
				.getSupportedPictureSizes();
		int format = params.getPreviewFormat();
		Size size = params.getPreviewSize();
		int[] CurPreRange = new int[2];
		params.getPreviewFpsRange(CurPreRange);
		params.setPreviewFpsRange(CurPreRange[0], CurPreRange[1]);

		// params.setPictureFormat(ImageFormat.JPEG);
		if (isBackCamera && DEFAULT_ORIENTATION != -1) {
			params.setRotation(DEFAULT_ORIENTATION);
		} else if (DEFAULT_ORIENTATION != -1) {
			params.setRotation(360 - DEFAULT_ORIENTATION);
		}
		Size targetSize = getTargetPreviewSize(supportSizes);
		if (targetSize != null) {
			params.setPictureSize(targetSize.width, targetSize.height);
		}
		try {
			mCamera.setParameters(params);
		} catch (Exception e) {
			logger.fine(e.getMessage());
		}
		int[] frameRates = new int[2];
		Log.w(TAG,
				"Camera properties: bpp=" + ImageFormat.getBitsPerPixel(format)
						+ "; format=" + format + "; size=" + size.width + "x"
						+ size.height + "; frameRates=" + frameRates[0] + "-"
						+ frameRates[1]);

		mCamera.setPreviewCallback(mJpegPreviewCallback);
		try {
			mCamera.startPreview(); // Recording is now started
		} catch (RuntimeException e) {
			stopCameraInternal();
			throw e;
		}

		mRecordingState = CameraState.RECORDING;
	}

相机的回调如下：这回调里，就可以拿到相机的数据，根据需要响应的处理了。

private PreviewCallback
mJpegPreviewCallback =
new Camera.PreviewCallback()
{

public
void onPreviewFrame(byte[]
data,
Camera camera)
{

}