说明
此时的SurfaceView主要是显示摄像头的数据， 不做其它功能用。
界面
<SurfaceView android:id="@+id/preview_view"
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>逻辑
hasSurface的使用
有效的避开重复的初始化listener。
1. 在onResume()中初始化
SurfaceView surfaceView = (SurfaceView) findViewById(R.id.preview_view);
SurfaceHolder surfaceHolder = surfaceView.getHolder();
if (hasSurface) {
// The activity was paused but not stopped, so the surface still exists. Therefore
// surfaceCreated() won't be called, so init the camera here.
initCamera(surfaceHolder);
} else {
// Install the callback and wait for surfaceCreated() to init the camera.
surfaceHolder.addCallback(this);
} initCamera()函数的解析
这个是重要的函数， 就是让SurfaceView显示出Camera的图像。
private void initCamera(SurfaceHolder surfaceHolder) {
if (surfaceHolder == null) {
throw new IllegalStateException("No SurfaceHolder provided");
}
if (cameraManager.isOpen()) {
Log.w(TAG, "initCamera() while already open -- late SurfaceView callback?");
return;
}
try {
cameraManager.openDriver(surfaceHolder);
// Creating the handler starts the preview, which can also throw a RuntimeException.
if (handler == null) {
handler = new CaptureActivityHandler(this, decodeFormats, decodeHints, characterSet, cameraManager);
}
decodeOrStoreSavedBitmap(null, null);
} catch (IOException ioe) {
Log.w(TAG, ioe);
displayFrameworkBugMessageAndExit();
} catch (RuntimeException e) {
// Barcode Scanner has seen crashes in the wild of this variety:
// java.?lang.?RuntimeException: Fail to connect to camera service
Log.w(TAG, "Unexpected error initializing camera", e);
displayFrameworkBugMessageAndExit();
}
} 仔细查看，主要是对CameraManager的使用。
CameraManger介绍
CmaeraManager主要是对摄像头的操控类，也是二维码数据的采集端。
CameraManager实例化
实在onResume中实例化的
cameraManager = new CameraManager(getApplication());openDriver(surfaceholder)函数的使用
/**
* Opens the camera driver and initializes the hardware parameters.
*
* @param holder The surface object which the camera will draw preview frames into.
* @throws IOException Indicates the camera driver failed to open.
*/
public synchronized void openDriver(SurfaceHolder holder) throws IOException {
OpenCamera theCamera = camera;
if (theCamera == null) {
theCamera = OpenCameraInterface.open(requestedCameraId);
if (theCamera == null) {
throw new IOException("Camera.open() failed to return object from driver");
}
camera = theCamera;
}
if (!initialized) {
initialized = true;
configManager.initFromCameraParameters(theCamera);
if (requestedFramingRectWidth > 0 && requestedFramingRectHeight > 0) {
setManualFramingRect(requestedFramingRectWidth, requestedFramingRectHeight);
requestedFramingRectWidth = 0;
requestedFramingRectHeight = 0;
}
}
Camera cameraObject = theCamera.getCamera();
Camera.Parameters parameters = cameraObject.getParameters();
String parametersFlattened = parameters == null ? null : parameters.flatten(); // Save these, temporarily
try {
configManager.setDesiredCameraParameters(theCamera, false);
} catch (RuntimeException re) {
// Driver failed
Log.w(TAG, "Camera rejected parameters. Setting only minimal safe-mode parameters");
Log.i(TAG, "Resetting to saved camera params: " + parametersFlattened);
// Reset:
if (parametersFlattened != null) {
parameters = cameraObject.getParameters();
parameters.unflatten(parametersFlattened);
try {
cameraObject.setParameters(parameters);
configManager.setDesiredCameraParameters(theCamera, true);
} catch (RuntimeException re2) {
// Well, darn. Give up
Log.w(TAG, "Camera rejected even safe-mode parameters! No configuration");
}
}
}
cameraObject.setPreviewDisplay(holder);
}主要是最后一句话，
cameraObject.setPreviewDisplay(holder);得到了Camera的数据。
OpenCameraInterface.open(requestedCameraId) 就是为了打开摄像头
/**
* Opens the requested camera with {@link Camera#open(int)}, if one exists.
*
* @param cameraId camera ID of the camera to use. A negative value
* or {@link #NO_REQUESTED_CAMERA} means "no preference", in which case a rear-facing
* camera is returned if possible or else any camera
* @return handle to {@link OpenCamera} that was opened
*/
public static OpenCamera open(int cameraId) {
int numCameras = Camera.getNumberOfCameras();
if (numCameras == 0) {
Log.w(TAG, "No cameras!");
return null;
}
boolean explicitRequest = cameraId >= 0;
Camera.CameraInfo selectedCameraInfo = null;
int index;
if (explicitRequest) {
index = cameraId;
selectedCameraInfo = new Camera.CameraInfo();
Camera.getCameraInfo(index, selectedCameraInfo);
} else {
index = 0;
while (index < numCameras) {
Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
Camera.getCameraInfo(index, cameraInfo);
CameraFacing reportedFacing = CameraFacing.values()[cameraInfo.facing];
if (reportedFacing == CameraFacing.BACK) {
selectedCameraInfo = cameraInfo;
break;
}
index++;
}
}
Camera camera;
if (index < numCameras) {
Log.i(TAG, "Opening camera #" + index);
camera = Camera.open(index);
} else {
if (explicitRequest) {
Log.w(TAG, "Requested camera does not exist: " + cameraId);
camera = null;
} else {
Log.i(TAG, "No camera facing " + CameraFacing.BACK + "; returning camera #0");
camera = Camera.open(0);
selectedCameraInfo = new Camera.CameraInfo();
Camera.getCameraInfo(0, selectedCameraInfo);
}
}
if (camera == null) {
return null;
}
return new OpenCamera(index,
camera,
CameraFacing.values()[selectedCameraInfo.facing],
selectedCameraInfo.orientation);
}