Android Camera的使用 （三)

一、创建一个Camear App

二、创建拍照功能
创建一拍照我们分以下几步：
1、检测和访问相机—–检测相机是否存在
2、创建一个用来预览的对象——创建一个 类继承自SurfaceView 并实现SurfaceHolder接口，这个类用来显示camera传来的图像。
3、创建布局——-创建不就用来放SurfaceView 以及控制按钮
4、设置监听器—设置监听器，当按钮点击时开始拍照或录像。
5、保存文件——-保存获得的图片或录像
6、释放相机

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1、检测相机
使用 PackageManager.hasSystemFeature() 方法

/** Check if this device has a camera */private boolean checkCameraHardware(Context context) {    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)){        // this device has a camera        return true;    } else {        // no camera on this device        return false;    }}

一个android设置可以有多个摄像头，android2.3（api 9)之后 可以使用 Camera.getNumberOfCameras() 获得相机数量。

2、访问相机
使用 Camera.open() 方法

/** A safe way to get an instance of the Camera object. */public static Camera getCameraInstance(){    Camera c = null;    try {        c = Camera.open(); // attempt to get a Camera instance    }    catch (Exception e){        // Camera is not available (in use or does not exist)    }    return c; // returns null if camera is unavailable}

在android 2.3 之后可以调用哦 Camera.open(int) 来打开指定的摄像头。

3、创建一个类继承自SurfaceView 并实现SurfaceHolder，来显示Camera拍摄的图像

/** A basic Camera preview class */public class CameraPreview extends SurfaceView implements SurfaceHolder.Callback {    private SurfaceHolder mHolder;    private Camera mCamera;    public CameraPreview(Context context, Camera camera) {        super(context);        mCamera = camera;        // Install a SurfaceHolder.Callback so we get notified when the        // underlying surface is created and destroyed.        mHolder = getHolder();        mHolder.addCallback(this);        // deprecated setting, but required on Android versions prior to 3.0        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);    }    public void surfaceCreated(SurfaceHolder holder) {        // The Surface has been created, now tell the camera where to draw the preview.        try {            mCamera.setPreviewDisplay(holder);            mCamera.startPreview();        } catch (IOException e) {            Log.d(TAG, "Error setting camera preview: " + e.getMessage());        }    }    public void surfaceDestroyed(SurfaceHolder holder) {        // empty. Take care of releasing the Camera preview in your activity.    }    public void surfaceChanged(SurfaceHolder holder, int format, int w, int h) {        // If your preview can change or rotate, take care of those events here.        // Make sure to stop the preview before resizing or reformatting it.        if (mHolder.getSurface() == null){          // preview surface does not exist          return;        }        // stop preview before making changes        try {            mCamera.stopPreview();        } catch (Exception e){          // ignore: tried to stop a non-existent preview        }        // set preview size and make any resize, rotate or        // reformatting changes here        // start preview with new settings        try {            mCamera.setPreviewDisplay(mHolder);            mCamera.startPreview();        } catch (Exception e){            Log.d(TAG, "Error starting camera preview: " + e.getMessage());        }    }}

4、设置布局

<?xml version="1.0" encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    android:orientation="horizontal"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    >  <FrameLayout    android:id="@+id/camera_preview"    android:layout_width="fill_parent"    android:layout_height="fill_parent"    android:layout_weight="1"    />  <Button    android:id="@+id/button_capture"    android:text="Capture"    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:layout_gravity="center"    /></LinearLayout>

将SurfaceView添加到 FrameLayout中

public class CameraActivity extends Activity {    private Camera mCamera;    private CameraPreview mPreview;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.main);        // Create an instance of Camera        mCamera = getCameraInstance();        // Create our Preview view and set it as the content of our activity.        mPreview = new CameraPreview(this, mCamera);        FrameLayout preview = (FrameLayout) findViewById(R.id.camera_preview);        preview.addView(mPreview);    }}

5、拍照
Camera.takePicture() 方法机型拍照，它接收 Camera.PictureCallback 类型的参数
，我们需要写一个类实现Camera.PictureCallback 接收JPEG图像，将图像数据写入文件

private PictureCallback mPicture = new PictureCallback() {    @Override    public void onPictureTaken(byte[] data, Camera camera) {        File pictureFile = getOutputMediaFile(MEDIA_TYPE_IMAGE);        if (pictureFile == null){            Log.d(TAG, "Error creating media file, check storage permissions: " +                e.getMessage());            return;        }        try {            FileOutputStream fos = new FileOutputStream(pictureFile);            fos.write(data);            fos.close();        } catch (FileNotFoundException e) {            Log.d(TAG, "File not found: " + e.getMessage());        } catch (IOException e) {            Log.d(TAG, "Error accessing file: " + e.getMessage());        }    }};

在点击按钮时触发：

// Add a listener to the Capture buttonButton captureButton = (Button) findViewById(id.button_capture);captureButton.setOnClickListener(    new View.OnClickListener() {        @Override        public void onClick(View v) {            // get an image from the camera            mCamera.takePicture(null, null, mPicture);        }    });

6、释放Camera
在结束后一定要释放Camera，调用Camera.release()方法

三、录像
录像我们需要结合 MediaRecorder类，当我们使用MediaRecorder，我们需要使用Camera的Camera.lock() 和 Camera.unlock()使得 MediaRecorder可以访问我们的Camera类
在android 4.0之后 camera.lock()和camera.ulock()被自动管理。

使用录像我们分以下几步：
1、打开相机—–调用 Camera.open()
2、设置预览——创建SurfaceView 并调用 Camera.setPreviewDisplay(). 设置SurfaceHoder
3、开始预览—–调用 Camera.startPreview()
4、开始录制视频
a、解锁Camera调用 Camera.unlock().
b、配置MediaRecord
1、setCamera()——–设置camera
2、setAudioSource()—使用 MediaRecorder.AudioSource.CAMCORDER.
3、setVideoSource() —- 使用MediaRecorder.VideoSource.CAMERA.
4、设置output format 在android2.2或者更高版，可以使用 MediaRecorder.setProfile（）方法和 CamcorderProfile.get() 设置。
①setOutputFormat() —–设置输出格式，可以是默认 或者MediaRecorder.OutputFormat.MPEG_4.
②setAudioEncoder() ——-设置声音编码，可以是默认或者 MediaRecorder.AudioEncoder.AMR_NB.
③、setVideoEncoder() —-可以是默认或者MediaRecorder.VideoEncoder.MPEG_4_SP.
5、setOutputFile() 设置输出文件路径
6、setPreviewDisplay() 这是SurfaceHolder
注意MediaRecorder 的设置应该按以上顺序执行，负责可能会crash,或者录制失败
c、调用MediaRecorder.prepare().
d、调用MediaRecorder.start().
5、停止录像
a、调用MediaRecorder.stop().
b、调用 MediaRecorder.reset(). 复位MediaRecorder的设置
c、调用MediaRecorder.release(). 释放MediaRecorder
d、调用Camera.lock().
6、停止预览 调用 Camera.stopPreview().
7、释放相机 调用 Camera.release().

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示例：

private boolean prepareVideoRecorder(){    mCamera = getCameraInstance();    mMediaRecorder = new MediaRecorder();    // Step 1: Unlock and set camera to MediaRecorder    mCamera.unlock();    mMediaRecorder.setCamera(mCamera);    // Step 2: Set sources    mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);    mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);    // Step 3: Set a CamcorderProfile (requires API Level 8 or higher)    mMediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH));    // Step 4: Set output file    mMediaRecorder.setOutputFile(getOutputMediaFile(MEDIA_TYPE_VIDEO).toString());    // Step 5: Set the preview output    mMediaRecorder.setPreviewDisplay(mPreview.getHolder().getSurface());    // Step 6: Prepare configured MediaRecorder    try {        mMediaRecorder.prepare();    } catch (IllegalStateException e) {        Log.d(TAG, "IllegalStateException preparing MediaRecorder: " + e.getMessage());        releaseMediaRecorder();        return false;    } catch (IOException e) {        Log.d(TAG, "IOException preparing MediaRecorder: " + e.getMessage());        releaseMediaRecorder();        return false;    }    return true;}

在android 2.2 之前 必须使用下面的替换第三步

 // Step 3: Set output format and encoding (for versions prior to API Level 8)    mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);    mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.DEFAULT);    mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.DEFAULT);

调用代码：

private boolean isRecording = false;// Add a listener to the Capture buttonButton captureButton = (Button) findViewById(id.button_capture);captureButton.setOnClickListener(    new View.OnClickListener() {        @Override        public void onClick(View v) {            if (isRecording) {                // stop recording and release camera                mMediaRecorder.stop();  // stop the recording                releaseMediaRecorder(); // release the MediaRecorder object                mCamera.lock();         // take camera access back from MediaRecorder                // inform the user that recording has stopped                setCaptureButtonText("Capture");                isRecording = false;            } else {                // initialize video camera                if (prepareVideoRecorder()) {                    // Camera is available and unlocked, MediaRecorder is prepared,                    // now you can start recording                    mMediaRecorder.start();                    // inform the user that recording has started                    setCaptureButtonText("Stop");                    isRecording = true;                } else {                    // prepare didn't work, release the camera                    releaseMediaRecorder();                    // inform user                }            }        }    });

释放相机

    private Camera mCamera;    private SurfaceView mPreview;    private MediaRecorder mMediaRecorder;    ...    @Override    protected void onPause() {        super.onPause();        releaseMediaRecorder();       // if you are using MediaRecorder, release it first        releaseCamera();              // release the camera immediately on pause event    }    private void releaseMediaRecorder(){        if (mMediaRecorder != null) {            mMediaRecorder.reset();   // clear recorder configuration            mMediaRecorder.release(); // release the recorder object            mMediaRecorder = null;            mCamera.lock();           // lock camera for later use        }    }    private void releaseCamera(){        if (mCamera != null){            mCamera.release();        // release the camera for other applications            mCamera = null;        }    }}

本文参考 https://developer.android.com/guide/topics/media/camera.html#saving-media