学习资料：

• 肾虚将军android camera2 详解说明
• 极客学院android.hardware.camera2 使用指南

Android 5.0(21)之后，android.hardware.Camera被废弃(下面称为Camera1)，还有一个android.graphics.Camera，这个android.graphics.Camera不是用来照相的，是用来处理图像的，可以做出3D的图像效果之类的，之前的Camera1则由android.hardware.Camera2来代替

Camera2支持RAW输出，可以调节曝光，对焦模式，快门等，功能比原先Camera强大

1.Camera1使用

使用步骤：

1. 调用Camera.open()，打开相机，默认为后置，可以根据摄像头ID来指定打开前置还是后置
2. 调用Camera.getParameters()得到一个Camera.Parameters对象
3. 使用步骤2得到的Camera.Parameters对象，对拍照参数进行设置
4. 调用Camera.setPreviewDispaly(SurfaceHolder holder)，指定使用哪个SurfaceView来显示预览图片
5. 调用Camera.startPreview()方法开始预览取景
6. 调用Camera.takePicture()方法进行拍照
7. 拍照结束后，调用Camera.stopPreview()结束取景预览，之后再replease()方法释放资源

这几个步骤从疯狂Android讲义中学到

1.1简单使用

使用SurfaceView进行取景的预览，点击屏幕进行拍照，用ImageView来展示拍的照片

取景

拍照预览

想买关于操作系统和C的书看，知乎很多人推荐这两本，就买了，感觉确实不错

布局文件：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <SurfaceView
        android:id="@+id/surface_view_camera2_activity"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

    <ImageView
        android:id="@+id/iv_show_camera2_activity"
        android:layout_width="180dp"
        android:layout_height="320dp"
        android:visibility="gone"
        android:layout_centerInParent="true"
        android:scaleType="centerCrop" />
</RelativeLayout>

Activity代码：

public class CameraActivity extends AppCompatActivity implements View.OnClickListener {

    private SurfaceView mSurfaceView;
    private SurfaceHolder mSurfaceHolder;
    private Camera mCamera;
    private ImageView iv_show;
    private int viewWidth, viewHeight;//mSurfaceView的宽和高

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera2);
        initView();
    }

    /**
     * 初始化控件
     */
    private void initView() {
        iv_show = (ImageView) findViewById(R.id.iv_show_camera2_activity);
        //mSurfaceView
        mSurfaceView = (SurfaceView) findViewById(R.id.surface_view_camera2_activity);
        mSurfaceHolder = mSurfaceView.getHolder();
        // mSurfaceView 不需要自己的缓冲区
        mSurfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        // mSurfaceView添加回调
        mSurfaceHolder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder holder) { //SurfaceView创建
                // 初始化Camera
                initCamera();
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) { //SurfaceView销毁
                // 释放Camera资源
                if (mCamera != null) {
                    mCamera.stopPreview();
                    mCamera.release();
                }
            }
        });
        //设置点击监听
        mSurfaceView.setOnClickListener(this);
    }

    @Override
    public void onWindowFocusChanged(boolean hasFocus) {
        super.onWindowFocusChanged(hasFocus);
        if (mSurfaceView != null) {
            viewWidth = mSurfaceView.getWidth();
            viewHeight = mSurfaceView.getHeight();
        }
    }

    /**
     * SurfaceHolder 回调接口方法
     */
    private void initCamera() {
        mCamera = Camera.open();//默认开启后置
        mCamera.setDisplayOrientation(90);//摄像头进行旋转90°
        if (mCamera != null) {
            try {
                Camera.Parameters parameters = mCamera.getParameters();
                //设置预览照片的大小
                parameters.setPreviewFpsRange(viewWidth, viewHeight);
                //设置相机预览照片帧数
                parameters.setPreviewFpsRange(4, 10);
                //设置图片格式
                parameters.setPictureFormat(ImageFormat.JPEG);
                //设置图片的质量
                parameters.set("jpeg-quality", 90);
                //设置照片的大小
                parameters.setPictureSize(viewWidth, viewHeight);
                //通过SurfaceView显示预览
                mCamera.setPreviewDisplay(mSurfaceHolder);
                //开始预览
                mCamera.startPreview();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 点击回调方法
     */
    @Override
    public void onClick(View v) {
        if (mCamera == null) return;
        //自动对焦后拍照
        mCamera.autoFocus(autoFocusCallback);
    }


    /**
     * 自动对焦 对焦成功后 就进行拍照
     */
    Camera.AutoFocusCallback autoFocusCallback = new Camera.AutoFocusCallback() {
        @Override
        public void onAutoFocus(boolean success, Camera camera) {
            if (success) {//对焦成功

                camera.takePicture(new Camera.ShutterCallback() {//按下快门
                    @Override
                    public void onShutter() {
                      //按下快门瞬间的操作
                    }
                }, new Camera.PictureCallback() {
                    @Override
                    public void onPictureTaken(byte[] data, Camera camera) {//是否保存原始图片的信息

                    }
                }, pictureCallback);
            }
        }
    };
    /**
     * 获取图片
     */
    Camera.PictureCallback pictureCallback = new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            final Bitmap resource = BitmapFactory.decodeByteArray(data, 0, data.length);
            if (resource == null) {
                Toast.makeText(CameraActivity.this, "拍照失败", Toast.LENGTH_SHORT).show();
            }
            final Matrix matrix = new Matrix();
            matrix.setRotate(90);
            final Bitmap bitmap = Bitmap.createBitmap(resource, 0, 0, resource.getWidth(), resource.getHeight(), matrix, true);
            if (bitmap != null && iv_show != null && iv_show.getVisibility() == View.GONE) {
                mCamera.stopPreview();
                iv_show.setVisibility(View.VISIBLE);
                mSurfaceView.setVisibility(View.GONE);
                Toast.makeText(CameraActivity.this, "拍照", Toast.LENGTH_SHORT).show();
                iv_show.setImageBitmap(bitmap);
            }
        }
    };
}

权限：

<uses-permission android:name="android.permission.CAMERA" />

在获得图片后，想要显示的效果是照片是竖直显示，resource显示的却是逆时针旋转了90°，照片是横着的，就使用matrix.setRotate(90)进行旋转

2.Camera2

Camera2拍照示意图

这里引用了管道的概念将安卓设备和摄像头之间联通起来，系统向摄像头发送 Capture 请求，而摄像头会返回 CameraMetadata。这一切建立在一个叫作 CameraCaptureSession 的会话中。

camera2中主要的类

以上从极客学院android.hardware.camera2 使用指南摘抄

• CameraManaer 摄像头管理器，用于检测摄像头，打开系统摄像头，调用CameraManager.getCameraCharacteristics(String)可以获取指定摄像头的相关特性
• CameraCharacteristics 摄像头的特性
• CameraDevice 摄像头，类似android.hardware.Camera也就是Camera1的Camera
• CameraCaptureSession 这个对象控制摄像头的预览或者拍照，setRepeatingRequest()开启预览，capture()拍照，CameraCaptureSession提供了StateCallback、CaptureCallback两个接口来监听CameraCaptureSession的创建和拍照过程。
• CameraRequest和CameraRequest.Builder，预览或者拍照时，都需要一个CameraRequest对象。CameraRequest表示一次捕获请求，用来对z照片的各种参数设置，比如对焦模式、曝光模式等。CameraRequest.Builder用来生成CameraRequest对象。

以上从肾虚将军的android camera2 详解说明摘抄

2.1 简单使用

使用的依然是SurfaceView来进行展示预览

主要思路：

1. 获得摄像头管理器CameraManager mCameraManager，mCameraManager.openCamera()来打开摄像头
2. 指定要打开的摄像头，并创建openCamera()所需要的CameraDevice.StateCallback stateCallback
3. 在CameraDevice.StateCallback stateCallback中调用takePreview()，这个方法中，使用CaptureRequest.Builder创建预览需要的CameraRequest，并初始化了CameraCaptureSession，最后调用了setRepeatingRequest(previewRequest, null, childHandler)进行了预览
4. 点击屏幕，调用takePicture()，这个方法内，最终调用了capture(mCaptureRequest, null, childHandler)
5. 在new ImageReader.OnImageAvailableListener(){}回调方法中，将拍照拿到的图片进行展示

代码：

public class Camera2Activity extends AppCompatActivity implements View.OnClickListener {
    private static final SparseIntArray ORIENTATIONS = new SparseIntArray();

    ///为了使照片竖直显示
    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);
    }

    private SurfaceView mSurfaceView;
    private SurfaceHolder mSurfaceHolder;
    private ImageView iv_show;
    private CameraManager mCameraManager;//摄像头管理器
    private Handler childHandler, mainHandler;
    private String mCameraID;//摄像头Id 0 为后  1 为前
    private ImageReader mImageReader;
    private CameraCaptureSession mCameraCaptureSession;
    private CameraDevice mCameraDevice;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera2);
        initVIew();
    }

    /**
     * 初始化
     */
    private void initVIew() {
        iv_show = (ImageView) findViewById(R.id.iv_show_camera2_activity);
        //mSurfaceView
        mSurfaceView = (SurfaceView) findViewById(R.id.surface_view_camera2_activity);
        mSurfaceView.setOnClickListener(this);
        mSurfaceHolder = mSurfaceView.getHolder();
        mSurfaceHolder.setKeepScreenOn(true);
        // mSurfaceView添加回调
        mSurfaceHolder.addCallback(new SurfaceHolder.Callback() {
            @Override
            public void surfaceCreated(SurfaceHolder holder) { //SurfaceView创建
                // 初始化Camera
                initCamera2();
            }

            @Override
            public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            }

            @Override
            public void surfaceDestroyed(SurfaceHolder holder) { //SurfaceView销毁
                // 释放Camera资源  
                if (null != mCameraDevice) {    
                    mCameraDevice.close(); 
                    Camera2Activity.this.mCameraDevice = null;
                }
            }
        });
    }

    /**
     * 初始化Camera2
     */
    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    private void initCamera2() {
        HandlerThread handlerThread = new HandlerThread("Camera2");
        handlerThread.start();
        childHandler = new Handler(handlerThread.getLooper());
        mainHandler = new Handler(getMainLooper());
        mCameraID = "" + CameraCharacteristics.LENS_FACING_FRONT;//后摄像头
        mImageReader = ImageReader.newInstance(1080, 1920, ImageFormat.JPEG,1);
        mImageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() { //可以在这里处理拍照得到的临时照片 例如，写入本地
            @Override
            public void onImageAvailable(ImageReader reader) {
                mCameraDevice.close();
                mSurfaceView.setVisibility(View.GONE);
                iv_show.setVisibility(View.VISIBLE);
                // 拿到拍照照片数据
                Image image = reader.acquireNextImage();
                ByteBuffer buffer = image.getPlanes()[0].getBuffer();
                byte[] bytes = new byte[buffer.remaining()];
                buffer.get(bytes);//由缓冲区存入字节数组
                final Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
                if (bitmap != null) {
                    iv_show.setImageBitmap(bitmap);
                }
            }
        }, mainHandler);
        //获取摄像头管理
        mCameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        try {
            if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
                return;
            }
            //打开摄像头
            mCameraManager.openCamera(mCameraID, stateCallback, mainHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }


    /**
     * 摄像头创建监听
     */
    private CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice camera) {//打开摄像头
            mCameraDevice = camera;
            //开启预览
            takePreview();
        }

        @Override
        public void onDisconnected(CameraDevice camera) {//关闭摄像头
            if (null != mCameraDevice) {
                mCameraDevice.close();
                Camera2Activity.this.mCameraDevice = null;
            }
        }

        @Override
        public void onError(CameraDevice camera, int error) {//发生错误
            Toast.makeText(Camera2Activity.this, "摄像头开启失败", Toast.LENGTH_SHORT).show();
        }
    };

    /**
     * 开始预览
     */
    private void takePreview() {
        try {
            // 创建预览需要的CaptureRequest.Builder
            final CaptureRequest.Builder previewRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            // 将SurfaceView的surface作为CaptureRequest.Builder的目标
            previewRequestBuilder.addTarget(mSurfaceHolder.getSurface());
            // 创建CameraCaptureSession，该对象负责管理处理预览请求和拍照请求
            mCameraDevice.createCaptureSession(Arrays.asList(mSurfaceHolder.getSurface(), mImageReader.getSurface()), new CameraCaptureSession.StateCallback() // ③
            {
                @Override
                public void onConfigured(CameraCaptureSession cameraCaptureSession) {
                    if (null == mCameraDevice) return;
                    // 当摄像头已经准备好时，开始显示预览
                    mCameraCaptureSession = cameraCaptureSession;
                    try {
                        // 自动对焦
                        previewRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
                        // 打开闪光灯
                        previewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
                        // 显示预览
                        CaptureRequest previewRequest = previewRequestBuilder.build();
                        mCameraCaptureSession.setRepeatingRequest(previewRequest, null, childHandler);
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                }

                @Override
                public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {
                    Toast.makeText(Camera2Activity.this, "配置失败", Toast.LENGTH_SHORT).show();
                }
            }, childHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    /**
     * 点击事件
     */
    @Override
    public void onClick(View v) {
        takePicture();
    }

    /**
     * 拍照
     */
    private void takePicture() {
        if (mCameraDevice == null) return;
       // 创建拍照需要的CaptureRequest.Builder
        final CaptureRequest.Builder captureRequestBuilder;
        try {
            captureRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            // 将imageReader的surface作为CaptureRequest.Builder的目标
            captureRequestBuilder.addTarget(mImageReader.getSurface());
            // 自动对焦
            captureRequestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
            // 自动曝光
            captureRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
            // 获取手机方向
            int rotation = getWindowManager().getDefaultDisplay().getRotation();
            // 根据设备方向计算设置照片的方向
            captureRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));
            //拍照
            CaptureRequest mCaptureRequest = captureRequestBuilder.build();
            mCameraCaptureSession.capture(mCaptureRequest, null, childHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }
}

布局代码以及权限与Camera1中一样，效果一样

预览时，是将mSurfaceHolder.getSurface()作为目标
显示拍照结果时，是将mImageReader.getSurface()作为目标

3.最后

Camera2的功能很强大，暂时也只是学习了最基本的思路

住的地方，没有桌子，于是坐地上，趴在床上敲代码，腰疼。逛淘宝买桌子去

感谢极客学院和肾虚将军的学习资料