java source code of CameraManager

package com.example.qrcode.camera;

/**
 * Created by yangyu on 17/10/18.
 */

import android.content.Context;
import android.graphics.Point;
import android.graphics.Rect;
import android.hardware.Camera;
import android.os.Handler;
import android.util.Log;
import android.view.SurfaceHolder;

import com.example.qrcode.callback.PreviewCallback;
import com.google.zxing.PlanarYUVLuminanceSource;

import java.io.IOException;

/**
 * This object wraps the Camera service object and expects to be the only one talking to it. The
 * implementation encapsulates the steps needed to take preview-sized images, which are used for
 * both preview and decoding.
 *
 * @author [email protected] (Daniel Switkin)
 */
@SuppressWarnings("deprecation") // camera APIs
public final class CameraManager {

    private static final String TAG = CameraManager.class.getSimpleName();

    private static final int MIN_FRAME_WIDTH = 240;
    private static final int MIN_FRAME_HEIGHT = 240;
    private static final int MAX_FRAME_WIDTH = 1200; // = 5/8 * 1920
    private static final int MAX_FRAME_HEIGHT = 675; // = 5/8 * 1080
    private static final int DEFAULT_TOP_PADDINF = 200;

    private final Context context;
    private final CameraConfigurationManager configManager;
    private OpenCamera camera;
    private AutoFocusManager autoFocusManager;
    private Rect framingRect;
    private boolean initialized;
    private boolean previewing;
    private int requestedCameraId = OpenCameraInterface.NO_REQUESTED_CAMERA;
    private int requestedFramingRectWidth;
    private int requestedFramingRectHeight;
    private int requestedFramingRectTopPadding;
    /**
     * Preview frames are delivered here, which we pass on to the registered handler. Make sure to
     * clear the handler so it will only receive one message.
     */
    private final PreviewCallback previewCallback;

    public CameraManager(Context context) {
        this.context = context;
        this.configManager = new CameraConfigurationManager(context);
        previewCallback = new PreviewCallback(configManager);
    }

    /**
     * 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
                        , requestedFramingRectTopPadding > 0 ? requestedFramingRectTopPadding : -1);
                requestedFramingRectWidth = 0;
                requestedFramingRectHeight = 0;
            }
        }

        Camera cameraObject = theCamera.getCamera();
        try {
            configManager.setDesiredCameraParameters(theCamera, false);
        } catch (RuntimeException re) {
        }
        cameraObject.setPreviewDisplay(holder);

    }

    public synchronized boolean isOpen() {
        return camera != null;
    }

    /**
     * Closes the camera driver if still in use.
     */
    public synchronized void closeDriver() {
        if (camera != null) {
            camera.getCamera().release();
            camera = null;
        }
    }

    public synchronized void clearFramingRect(){
        // Make sure to clear these each time we close the camera, so that any scanning rect
        // requested by intent is forgotten.
        framingRect = null;
    }

    /**
     * Asks the camera hardware to begin drawing preview frames to the screen.
     */
    public synchronized void startPreview() {
        OpenCamera theCamera = camera;
        if (theCamera != null && !previewing) {
            theCamera.getCamera().startPreview();
            previewing = true;
            autoFocusManager = new AutoFocusManager(context, theCamera.getCamera());
        }
    }

    /**
     * Tells the camera to stop drawing preview frames.
     */
    public synchronized void stopPreview() {
        if (autoFocusManager != null) {
            autoFocusManager.stop();
            autoFocusManager = null;
        }
        if (camera != null && previewing) {
            camera.getCamera().stopPreview();
            previewCallback.setHandler(null, 0);
            previewing = false;
        }
    }

    /**
     * @param newSetting if {@code true}, light should be turned on if currently off. And vice versa.
     */
    public synchronized void setTorch(boolean newSetting) {
        OpenCamera theCamera = camera;
        if (theCamera != null && newSetting != configManager.getTorchState(theCamera.getCamera())) {
            boolean wasAutoFocusManager = autoFocusManager != null;
            if (wasAutoFocusManager) {
                autoFocusManager.stop();
                autoFocusManager = null;
            }
            configManager.setTorch(theCamera.getCamera(), newSetting);
            if (wasAutoFocusManager) {
                autoFocusManager = new AutoFocusManager(context, theCamera.getCamera());
                autoFocusManager.start();
            }
        }
    }

    /**
     * A single preview frame will be returned to the handler supplied. The data will arrive as byte[]
     * in the message.obj field, with width and height encoded as message.arg1 and message.arg2,
     * respectively.
     *
     * @param handler The handler to send the message to.
     * @param message The what field of the message to be sent.
     */
    public synchronized void requestPreviewFrame(Handler handler, int message) {
        OpenCamera theCamera = camera;
        if (theCamera != null && previewing) {
            previewCallback.setHandler(handler, message);
            theCamera.getCamera().setOneShotPreviewCallback(previewCallback);
        }
    }

    /**
     * Calculates the framing rect which the UI should draw to show the user where to place the
     * barcode. This target helps with alignment as well as forces the user to hold the device
     * far enough away to ensure the image will be in focus.
     *
     * @return The rectangle to draw on screen in window coordinates.
     */
    public synchronized Rect getFramingRect() {
        if (framingRect == null) {
            if (camera == null) {
                return null;
            }
            Point screenResolution = configManager.getScreenResolution();
            if (screenResolution == null) {
                // Called early, before init even finished
                return null;
            }

            int width = findDesiredDimensionInRange(screenResolution.x, MIN_FRAME_WIDTH, MAX_FRAME_WIDTH);
            int height = findDesiredDimensionInRange(screenResolution.y, MIN_FRAME_HEIGHT, MAX_FRAME_HEIGHT);

            int leftOffset = (screenResolution.x - width) / 2;
            int topOffset = DEFAULT_TOP_PADDINF;
            framingRect = new Rect(leftOffset, topOffset, leftOffset + width, topOffset + height);
            Log.d(TAG, "Calculated framing rect: " + framingRect);
        }
        return framingRect;
    }

    private static int findDesiredDimensionInRange(int resolution, int hardMin, int hardMax) {
        int dim = 5 * resolution / 8; // Target 5/8 of each dimension
        if (dim < hardMin) {
            return hardMin;
        }
        if (dim > hardMax) {
            return hardMax;
        }
        return dim;
    }

//    /**
//     * Like {@link #getFramingRect} but coordinates are in terms of the preview frame,
//     * not UI / screen.
//     *
//     * @return {@link Rect} expressing barcode scan area in terms of the preview size
//     */
//    public synchronized Rect getFramingRectInPreview() {
//        if (framingRectInPreview == null) {
//            Rect framingRect = getFramingRect();
//            if (framingRect == null) {
//                return null;
//            }
//            Rect rect = new Rect(framingRect);
//            Point cameraResolution = configManager.getCameraResolution();
//            Point screenResolution = configManager.getScreenResolution();
//            if (cameraResolution == null || screenResolution == null) {
//                // Called early, before init even finished
//                return null;
//            }
//            rect.left = rect.left * cameraResolution.x / screenResolution.x;
//            rect.right = rect.right * cameraResolution.x / screenResolution.x;
//            rect.top = rect.top * cameraResolution.y / screenResolution.y;
//            rect.bottom = rect.bottom * cameraResolution.y / screenResolution.y;
//            framingRectInPreview = rect;
//        }
//        return framingRectInPreview;
//    }


    /**
     * 设置camera ID
     *
     * @param cameraId camera ID of the camera to use. A negative value means "no preference".
     */
    public synchronized void setManualCameraId(int cameraId) {
        requestedCameraId = cameraId;
    }

    /**
     * 设置扫码框的大小
     *
     * @param width  The width in pixels to scan.
     * @param height The height in pixels to scan.
     */
    public synchronized void setManualFramingRect(int width, int height, int topPadding) {
        if (initialized) {
            Point screenResolution = configManager.getScreenResolution();
            if (width > screenResolution.x) {
                width = screenResolution.x;
            }
            if (height > screenResolution.y) {
                height = screenResolution.y;
            }
            int leftOffset = (screenResolution.x - width) / 2;
            int topOffset = topPadding < 0 ? DEFAULT_TOP_PADDINF : topPadding;
            framingRect = new Rect(leftOffset, topOffset, leftOffset + width, topOffset + height);
        } else {
            requestedFramingRectWidth = width;
            requestedFramingRectHeight = height;
            requestedFramingRectTopPadding = topPadding;
        }
    }

    /**
     * A factory method to build the appropriate LuminanceSource object based on the format
     * of the preview buffers, as described by Camera.Parameters.
     *
     * @param data   A preview frame.
     * @param width  The width of the image.
     * @param height The height of the image.
     * @return A PlanarYUVLuminanceSource instance.
     */
    public PlanarYUVLuminanceSource buildLuminanceSource(byte[] data, int width, int height) {
        return new PlanarYUVLuminanceSource(data, width, height, 0, 0,
                width, height, false);
    }

}