Android Camera的使用 （一）

一、前言
在android 5.0 之后 官方已经不推荐Camear这个类了，而是推荐 android.hardware.camera2 包下的api.但我们还是有必要学习一下。

Camera这个类可以被用来照相、start/top相机预览、将图像帧编码成video。它对于相机服务相当于一个客户端，它管理者真正的硬件Camera。

要访问硬件Camera我们必须在AndroidManifest.xml中声明相机权限。还必须确保AndroidManifest.xml 包含相机功能的声明( < uses- feature >)。比如如果想使用相机的 auto-focus，就必须在AndroidManifest.xml中声明：

<uses-permission android:name="android.permission.CAMERA" /> <uses-feature android:name="android.hardware.camera" /> <uses-feature android:name="android.hardware.camera.autofocus" />

使用这个类照相可以分为以下几步：
1、使用 Camera的 opent(int).创建一个实例
2、通过getParameters(). 获得默认的参数
3、如果必要的话，通过setParameters(Camera.Parameters). 修改参数
4、使用 setDisplayOrientation(int)改正当前预览的方向
5、初始化一个SurfaceHolder,并通过 setPreviewDisplay(SurfaceHolder). 设置，如果没有设置将不能开始预览
6、 调用startPreview()开始预览，拍照前必须开始预览
7、调用 takePicture(Camera.ShutterCallback, Camera.PictureCallback, Camera.PictureCallback, Camera.PictureCallback) 等待image 数据
8、拍完照之后，如果还想继续拍照重新调用 startPreview()
9、调用 stopPreview()停止预览
10、调用 release() 释放。应用程序应该在 onPause()时立即调用该方法，在onResume重新打开。

使用这个类录像分为以下几步：
1、和上文描述的一样 创建一个实例，之后开启预览
2、调用unlock() 去允许media process 访问camera
3、通过MediaRecord的 setCamera(Camear camera)
4、当结束录制之后，调用reconnect() 去请求，并re-lock Camera
5、如果希望继续拍照或者录像，重新调用 startPreviews()
6、调用stopPreview(） 和 release()结束

下面是一个简单的拍照示例：

public class CameraActivity extends BaseActivity {    private static final String TAG = "CameraActivity";    @BindView(R.id.btn_take_picture)    Button btnTakePicture;    @BindView(R.id.btn_start_record)    Button btnStartRecord;    @BindView(R.id.surfaceView)    SurfaceView surfaceView;    private SurfaceHolder holder;    private Camera mCamera;    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.act_camera);        ButterKnife.bind(this);        initView();    }    private void initCamera() {        /**         * Step 1.         * 获得一个Camera实例，（默认获得为后置摄像头)         */        if(mCamera==null){            mCamera = Camera.open();        }        /**         * Step 2.         * 获得默认的参数         */        Camera.Parameters parameters = mCamera.getParameters();        parameters.setPictureFormat(ImageFormat.JPEG);        /**         * Stop 3.         * 设置参数         */        mCamera.setParameters(parameters);        /**         * Step 4.         * 修正当前的方向         */        setCameraDisplayOrientation(this, Camera.CameraInfo.CAMERA_FACING_BACK, mCamera);        /**         * Step 5.         * 设置 SurfaceHolder         */        try {            mCamera.setPreviewDisplay(holder);        } catch (IOException e) {            e.printStackTrace();        }        /**         * Step 6.         * 开始预览         */        mCamera.startPreview();    }    public static void setCameraDisplayOrientation(Activity activity,                                                   int cameraId, android.hardware.Camera camera) {        android.hardware.Camera.CameraInfo info =                new android.hardware.Camera.CameraInfo();        android.hardware.Camera.getCameraInfo(cameraId, info);        int rotation = activity.getWindowManager().getDefaultDisplay()                .getRotation();        int degrees = 0;        switch (rotation) {            case Surface.ROTATION_0:                degrees = 0;                break;            case Surface.ROTATION_90:                degrees = 90;                break;            case Surface.ROTATION_180:                degrees = 180;                break;            case Surface.ROTATION_270:                degrees = 270;                break;        }        int result;        if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {            result = (info.orientation + degrees) % 360;            result = (360 - result) % 360;  // compensate the mirror        } else {  // back-facing            result = (info.orientation - degrees + 360) % 360;        }        camera.setDisplayOrientation(result);    }    private void initView() {        holder = surfaceView.getHolder();        holder.addCallback(callback);        holder.setKeepScreenOn(true);    }    @Override    protected void onResume() {        super.onResume();        Log.i(TAG, "onResume: ");        initCamera();    }    @Override    protected void onPause() {        super.onPause();        Log.i(TAG, "onPause: ");        /**         * Step 9. 停止预览         */        mCamera.stopPreview();        /**         * Step 10. 释放         */        mCamera.release();        mCamera = null;    }    @OnClick({R.id.btn_take_picture, R.id.btn_start_record})    public void onClick(View view) {        switch (view.getId()) {            case R.id.btn_take_picture:                /**                 * Step 7.                 * 拍照                 */                mCamera.takePicture(null, null, null, new Camera.PictureCallback() {                    @Override                    public void onPictureTaken(byte[] data, Camera camera) {                        if (data != null) {                            /**                             * Step 8. 重新开始预览                             */                            mCamera.startPreview();                            writeImage2Sdcard(data);                        }                    }                });                break;            case R.id.btn_start_record:                break;        }    }    private void writeImage2Sdcard(final byte[] data) {        new Thread() {            @Override            public void run() {                FileOutputStream out = null;                try {                    out = new FileOutputStream(new File("sdcard/test",                            System.currentTimeMillis() + ".jpg"));                    out.write(data);                } catch (FileNotFoundException e) {                    e.printStackTrace();                } catch (IOException e) {                    e.printStackTrace();                } finally {                    if (out != null) try {                        out.close();                    } catch (IOException e) {                        e.printStackTrace();                    }                }            }        }.start();    }    private SurfaceHolder.Callback callback = new SurfaceHolder.Callback() {        @Override        public void surfaceCreated(SurfaceHolder holder) {            initCamera();            Log.i(TAG, "surfaceCreated: ");        }        @Override        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {            Log.i(TAG, "surfaceChanged: ");            setCameraDisplayOrientation(CameraActivity.this,                    Camera.CameraInfo.CAMERA_FACING_BACK,mCamera);        }        @Override        public void surfaceDestroyed(SurfaceHolder holder) {            Log.i(TAG, "surfaceDestroyed: ");        }    };

如果需要录制视频的话加入以下代码：

 if (!started) {                    started = true;                    btnStartRecord.setText("结束录像");                    mediaRecorder = new MediaRecorder();                    /**                     * 录像 Step A.                     */                    mCamera.unlock();                    /**                     * 录像 Step B.                     */                    mediaRecorder.setCamera(mCamera);                    mediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);                    mediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);                    mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);//                    mediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH));                    mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);                    mediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.MPEG_4_SP);                    mediaRecorder.setOutputFile(Environment.getExternalStorageDirectory()+                            File.separator+System.currentTimeMillis()+".3gp");                    try {                        mediaRecorder.prepare();                    } catch (IOException e) {                        e.printStackTrace();                    }                    mediaRecorder.start();//                } else {                    started = false;                    btnStartRecord.setText("开始录像");                    mediaRecorder.stop();                    mediaRecorder.reset();                    mediaRecorder.release();                    /**                     * 录像 Step C.                     */                    try {                        mCamera.reconnect();                    } catch (IOException e) {                        e.printStackTrace();                    }                    mCamera.lock();                    /**                     * 录像 Step D.                     */                    mCamera.startPreview();                }

最后完整代码如下：

public class CameraActivity extends BaseActivity {    private static final String TAG = "CameraActivity";    @BindView(R.id.btn_take_picture)    Button btnTakePicture;    @BindView(R.id.btn_start_record)    Button btnStartRecord;    @BindView(R.id.surfaceView)    SurfaceView surfaceView;    private SurfaceHolder holder;    private Camera mCamera;    private MediaRecorder mediaRecorder;    private boolean started;    @Override    protected void onCreate(@Nullable Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.act_camera);        ButterKnife.bind(this);        initView();    }    private void initCamera() {        /**         * Step 1.         * 获得一个Camera实例，（默认获得为后置摄像头)         */        if (mCamera == null) {            mCamera = Camera.open();        }        /**         * Step 2.         * 获得默认的参数         */        Camera.Parameters parameters = mCamera.getParameters();        parameters.setPictureFormat(ImageFormat.JPEG);        /**         * Stop 3.         * 设置参数         */        mCamera.setParameters(parameters);        /**         * Step 4.         * 修正当前的方向         */        setCameraDisplayOrientation(this, Camera.CameraInfo.CAMERA_FACING_BACK, mCamera);        /**         * Step 5.         * 设置 SurfaceHolder         */        try {            mCamera.setPreviewDisplay(holder);        } catch (IOException e) {            e.printStackTrace();        }        /**         * Step 6.         * 开始预览         */        mCamera.startPreview();    }    public static void setCameraDisplayOrientation(Activity activity,                                                   int cameraId, android.hardware.Camera camera) {        android.hardware.Camera.CameraInfo info =                new android.hardware.Camera.CameraInfo();        android.hardware.Camera.getCameraInfo(cameraId, info);        int rotation = activity.getWindowManager().getDefaultDisplay()                .getRotation();        int degrees = 0;        switch (rotation) {            case Surface.ROTATION_0:                degrees = 0;                break;            case Surface.ROTATION_90:                degrees = 90;                break;            case Surface.ROTATION_180:                degrees = 180;                break;            case Surface.ROTATION_270:                degrees = 270;                break;        }        int result;        if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {            result = (info.orientation + degrees) % 360;            result = (360 - result) % 360;  // compensate the mirror        } else {  // back-facing            result = (info.orientation - degrees + 360) % 360;        }        camera.setDisplayOrientation(result);    }    private void initView() {        holder = surfaceView.getHolder();        holder.addCallback(callback);        holder.setKeepScreenOn(true);    }    @Override    protected void onResume() {        super.onResume();        Log.i(TAG, "onResume: ");        initCamera();    }    @Override    protected void onPause() {        super.onPause();        Log.i(TAG, "onPause: ");        /**         * Step 9. 停止预览         */        mCamera.stopPreview();        /**         * Step 10. 释放         */        mCamera.release();        mCamera = null;    }    @OnClick({R.id.btn_take_picture, R.id.btn_start_record})    public void onClick(View view) {        switch (view.getId()) {            case R.id.btn_take_picture:                /**                 * Step 7.                 * 拍照                 */                mCamera.takePicture(null, null, null, new Camera.PictureCallback() {                    @Override                    public void onPictureTaken(byte[] data, Camera camera) {                        if (data != null) {                            /**                             * Step 8. 重新开始预览                             */                            mCamera.startPreview();                            writeImage2Sdcard(data);                        }                    }                });                break;            case R.id.btn_start_record:                if (!started) {                    started = true;                    btnStartRecord.setText("结束录像");                    mediaRecorder = new MediaRecorder();                    /**                     * 录像 Step A.                     */                    mCamera.unlock();                    /**                     * 录像 Step B.                     */                    mediaRecorder.setCamera(mCamera);                    mediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);                    mediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);                    mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);//                    mediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH));                    mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AMR_NB);                    mediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.MPEG_4_SP);                    mediaRecorder.setOutputFile(Environment.getExternalStorageDirectory()+                            File.separator+System.currentTimeMillis()+".3gp");                    try {                        mediaRecorder.prepare();                    } catch (IOException e) {                        e.printStackTrace();                    }                    mediaRecorder.start();//                } else {                    started = false;                    btnStartRecord.setText("开始录像");                    mediaRecorder.stop();                    mediaRecorder.reset();                    mediaRecorder.release();                    /**                     * 录像 Step C.                     */                    try {                        mCamera.reconnect();                    } catch (IOException e) {                        e.printStackTrace();                    }                    mCamera.lock();                    /**                     * 录像 Step D.                     */                    mCamera.startPreview();                }                break;        }    }    private void writeImage2Sdcard(final byte[] data) {        new Thread() {            @Override            public void run() {                FileOutputStream out = null;                try {                    out = new FileOutputStream(new File("sdcard/test",                            System.currentTimeMillis() + ".jpg"));                    out.write(data);                } catch (FileNotFoundException e) {                    e.printStackTrace();                } catch (IOException e) {                    e.printStackTrace();                } finally {                    if (out != null) try {                        out.close();                    } catch (IOException e) {                        e.printStackTrace();                    }                }            }        }.start();    }    private SurfaceHolder.Callback callback = new SurfaceHolder.Callback() {        @Override        public void surfaceCreated(SurfaceHolder holder) {            initCamera();            Log.i(TAG, "surfaceCreated: ");        }        @Override        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {            Log.i(TAG, "surfaceChanged: ");            setCameraDisplayOrientation(CameraActivity.this,                    Camera.CameraInfo.CAMERA_FACING_BACK, mCamera);        }        @Override        public void surfaceDestroyed(SurfaceHolder holder) {            Log.i(TAG, "surfaceDestroyed: ");        }    };}

权限:

 <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"></uses-permission>    <uses-permission android:name="android.permission.INTERNET"></uses-permission>    <uses-permission android:name="android.permission.CAMERA"></uses-permission>    <uses-feature android:name="android.hardware.camera"></uses-feature>    <uses-feature android:name="android.hardware.camera.autofocus"></uses-feature>    <uses-permission android:name="android.permission.RECORD_AUDIO" />