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Android Camera2教程之打开相机、开启预览、实现PreviewCallback、拍照

转载请注明出处: http://blog.csdn.net/lb377463323/article/details/52740411

Android API 21新增了Camera2,这与之前的camera架构完全不同,使用起来也比较复杂,但是功能变得很强大。

在讲解开启预览之前,首先需要了解camera2的几个比较重要的类:

  • CameraManager: 管理手机上的所有摄像头设备,它的作用主要是获取摄像头列表和打开指定的摄像头
  • CameraDevice: 具体的摄像头设备,它有一系列参数(预览尺寸、拍照尺寸等),可以通过CameraManager的getCameraCharacteristics()方法获取。它的作用主要是创建CameraCaptureSession和CaptureRequest
  • CameraCaptureSession: 相机捕获会话,用于处理拍照和预览的工作(很重要)
  • CaptureRequest: 捕获请求,定义输出缓冲区以及显示界面(TextureView或SurfaceView)等

1,定义TextureView作为预览界面

在布局文件中加入TextureView控件,然后实现其监听事件

textureView = (TextureView) findViewById(R.id.textureView);

然后我们可以在OnResume()方法中设置监听SurefaceTexture的事件

textureView.setSurfaceTextureListener(textureListener);

当SurefaceTexture准备好后会回调SurfaceTextureListener 的onSurfaceTextureAvailable()方法

TextureView.SurfaceTextureListener textureListener = new TextureView.SurfaceTextureListener() {
    @Override
    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
        //当SurefaceTexture可用的时候,设置相机参数并打开相机
        setupCamera(width, height);
        openCamera();
    }
};

2,设置相机参数

为了更好地预览,我们根据TextureView的尺寸设置预览尺寸,Camera2中使用CameraManager来管理摄像头

private void setupCamera(int width, int height) {
        //获取摄像头的管理者CameraManager
    CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
    try {
        //遍历所有摄像头
        for (String cameraId: manager.getCameraIdList()) {
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
            //默认打开后置摄像头
            if (characteristics.get(CameraCharacteristics.LENS_FACING) == CameraCharacteristics.LENS_FACING_FRONT)
                continue;
            //获取StreamConfigurationMap,它是管理摄像头支持的所有输出格式和尺寸
            StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            //根据TextureView的尺寸设置预览尺寸
            mPreviewSize = getOptimalSize(map.getOutputSizes(SurfaceTexture.class), width, height);
            mCameraId = cameraId;
            break;
        }
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

3,开启相机

Camera2中打开相机也需要通过CameraManager类

private void openCamera() {
    //获取摄像头的管理者CameraManager
    CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
    //检查权限
    try {
        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
            return;
        }
        //打开相机,第一个参数指示打开哪个摄像头,第二个参数stateCallback为相机的状态回调接口,第三个参数用来确定Callback在哪个线程执行,为null的话就在当前线程执行
        manager.openCamera(mCameraId, stateCallback, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

实现StateCallback 接口,当相机打开后会回调onOpened方法,在这个方法里面开启预览

private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
    @Override
    public void onOpened(CameraDevice camera) {
        mCameraDevice = camera;
        //开启预览
        startPreview();
    }
}

4,开启相机预览

我们使用TextureView显示相机预览数据,Camera2的预览和拍照数据都是使用CameraCaptureSession会话来请求的

private void startPreview() {
    SurfaceTexture mSurfaceTexture = mTextureView.getSurfaceTexture();
    //设置TextureView的缓冲区大小
    mSurfaceTexture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
    //获取Surface显示预览数据
    Surface mSurface = new Surface(mSurfaceTexture);
    try {
        //创建CaptureRequestBuilder,TEMPLATE_PREVIEW比表示预览请求
        mCaptureRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
        //设置Surface作为预览数据的显示界面
        mCaptureRequestBuilder.addTarget(mSurface);
        //创建相机捕获会话,第一个参数是捕获数据的输出Surface列表,第二个参数是CameraCaptureSession的状态回调接口,当它创建好后会回调onConfigured方法,第三个参数用来确定Callback在哪个线程执行,为null的话就在当前线程执行
        mCameraDevice.createCaptureSession(Arrays.asList(mSurface), new CameraCaptureSession.StateCallback() {
            @Override
            public void onConfigured(CameraCaptureSession session) {
                try {
                        //创建捕获请求
                        mCaptureRequest = mCaptureRequestBuilder.build();
                        mPreviewSession = session;
                        //设置反复捕获数据的请求,这样预览界面就会一直有数据显示
                        mPreviewSession.setRepeatingRequest(mCaptureRequest, mSessionCaptureCallback, null);
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                }

            @Override
            public void onConfigureFailed(CameraCaptureSession session) {

            }
        }, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
}

5,实现PreviewCallback

Camera2中并没有Camera1中的PreviewCallback接口,那怎么实现获取预览帧数据呢?答案就是使用ImageReader间接实现

首先创建一个ImageReader,并监听它的事件

private void setupImageReader() {
    //前三个参数分别是需要的尺寸和格式,最后一个参数代表每次最多获取几帧数据,本例的2代表ImageReader中最多可以获取两帧图像流
    mImageReader = ImageReader.newInstance(mPreviewSize.getWidth(), mPreviewSize.getHeight(),
                ImageFormat.JPEG, 2);
    //监听ImageReader的事件,当有图像流数据可用时会回调onImageAvailable方法,它的参数就是预览帧数据,可以对这帧数据进行处理
    mImageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            Image image = reader.acquireLatestImage();
            //我们可以将这帧数据转成字节数组,类似于Camera1的PreviewCallback回调的预览帧数据
            ByteBuffer buffer = image.getPlanes()[0].getBuffer();
            byte[] data = new byte[buffer.remaining()];
            buffer.get(data);
            image.close();
        }
    }, null);
}

注意:一定要调用reader.acquireLatestImage()和close()方法,否则画面就会卡住

然后我们在开启预览之前,设置ImageReader为输出Surface

setupImageReader();

//获取ImageReader的Surface
Surface imageReaderSurface = mImageReader.getSurface();

//CaptureRequest添加imageReaderSurface,不加的话就会导致ImageReader的onImageAvailable()方法不会回调
mCaptureRequestBuilder.addTarget(imageReaderSurface);

//创建CaptureSession时加上imageReaderSurface,如下,这样预览数据就会同时输出到previewSurface和imageReaderSurface了
mCameraDevice.createCaptureSession(Arrays.asList(previewSurface, imageReaderSurface), new CameraCaptureSession.StateCallback() {

}

关闭相机时别忘了关闭ImageReader

6,拍照

Camera2拍照也是通过ImageReader来实现的

首先先做些准备工作,设置拍照参数,如方向、尺寸等

private static final SparseIntArray ORIENTATION = new SparseIntArray();
    static {
        ORIENTATION.append(Surface.ROTATION_0, 90);
        ORIENTATION.append(Surface.ROTATION_90, 0);
        ORIENTATION.append(Surface.ROTATION_180, 270);
        ORIENTATION.append(Surface.ROTATION_270, 180);
    }

设置拍照尺寸,可以跟预览尺寸一起设置,然后ImageReader初始化使用此尺寸

mCaptureSize = Collections.max(Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)), new Comparator<Size>() {
                    @Override
                    public int compare(Size lhs, Size rhs) {
                        return Long.signum(lhs.getWidth() * lhs.getHeight() - rhs.getHeight() * rhs.getWidth());
                    }
                });

创建保存图片的线程

public static class imageSaver implements Runnable {
        private Image mImage;
        public imageSaver(Image image) {
            mImage = image;
        }
        @Override
        public void run() {
            ByteBuffer buffer = mImage.getPlanes()[0].getBuffer();
            byte[] data = new byte[buffer.remaining()];
            buffer.get(data);
            mImageFile = new File(Environment.getExternalStorageDirectory() + "/DCIM/myPicture.jpg");
            FileOutputStream fos = null;
            try {
                fos = new FileOutputStream(mImageFile);
                fos.write(data, 0 ,data.length);
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                mImageFile = null;
                if (fos != null) {
                    try {
                        fos.close();
                        fos = null;
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

然后当ImageReader有数据时,通过此线程保存图片

//使用前面获取的拍照尺寸
mImageReader = ImageReader.newInstance(mCaptureSize.getWidth(), mCaptureSize.getHeight(),
                ImageFormat.JPEG, 2);
mImageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {
            @Override
            public void onImageAvailable(ImageReader reader) {
                //执行图像保存子线程
                mCameraHandler.post(new imageSaver(reader.acquireNextImage()));
            }
        }, mCameraHandler);

然后开启预览创建CaptureSession时把ImageReader添加进去

mCameraDevice.createCaptureSession(Arrays.asList(previewSurface, mImageReader.getSurface()), new CameraCaptureSession.StateCallback() { 
}

现在准备工作做好了,还需要响应点击拍照事件,我们设置点击拍照按钮调用capture()方法,capture()方法即实现拍照

private void capture() {
        try {
            //首先我们创建请求拍照的CaptureRequest
            final CaptureRequest.Builder mCaptureBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            //获取屏幕方向
            int rotation = getWindowManager().getDefaultDisplay().getRotation();
            //设置CaptureRequest输出到mImageReader
            mCaptureBuilder.addTarget(mImageReader.getSurface());
            //设置拍照方向
            mCaptureBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATION.get(rotation));
            //这个回调接口用于拍照结束时重启预览,因为拍照会导致预览停止
            CameraCaptureSession.CaptureCallback mImageSavedCallback = new CameraCaptureSession.CaptureCallback() {
                @Override
                public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
                    Toast.makeText(getApplicationContext(), "Image Saved!", Toast.LENGTH_SHORT).show();
                    //重启预览
                    restartPreview();
                }
            };
            //停止预览
            mCameraCaptureSession.stopRepeating();
            //开始拍照,然后回调上面的接口重启预览,因为mCaptureBuilder设置ImageReader作为target,所以会自动回调ImageReader的onImageAvailable()方法保存图片
            mCameraCaptureSession.capture(mCaptureBuilder.build(), mImageSavedCallback, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

重启预览的方法很简单了

 private void restartPreview() {
        try {
        //执行setRepeatingRequest方法就行了,注意mCaptureRequest是之前开启预览设置的请求
                       mCameraCaptureSession.setRepeatingRequest(mCaptureRequest, null, mCameraHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

代码地址(顺手给个Star啊):点击查看源码



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