原文:

上一篇博文简单介绍了使用Camera2 API拍摄照片，并使用SurfaceView作为预览界面。实际上，相对于SurfaceView, TextureView更适合用于视频和拍摄照片。SurfaceView也有它的使用场合，这将在另外一篇中阐述。本文将使用TextureView作为预览界面，再次向大家展示Camera2 API的简单应用。

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

private TextureView.SurfaceTextureListener mTextureListener = 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();        }        @Override        public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {        }        @Override        public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {            return false;        }        @Override        public void onSurfaceTextureUpdated(SurfaceTexture surface) {        }    };

2，设置相机参数

private void setupCamera(int width, int height) {        //获取摄像头的管理者CameraManager        CameraManager manager = (CameraManager) getContext().getSystemService(Context.CAMERA_SERVICE);        try {            //遍历所有摄像头            for (String cameraId : manager.getCameraIdList()) {                CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);                Integer facing = characteristics.get(CameraCharacteristics.LENS_FACING);                //此处默认打开后置摄像头                if (facing != null && 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);                assert map != null;                //根据TextureView的尺寸设置预览尺寸                mPreviewSize = getOptimalSize(map.getOutputSizes(SurfaceTexture.class), width, height);                //获取相机支持的最大拍照尺寸                mCaptureSize = Collections.max(Arrays.asList(map.getOutputSizes(ImageFormat.JPEG)), new Comparator
     
      () {                    @Override                    public int compare(Size lhs, Size rhs) {                        return Long.signum(lhs.getWidth() * lhs.getHeight() - rhs.getHeight() * rhs.getWidth());                    }                });                //此ImageReader用于拍照所需                setupImageReader();                mCameraId = cameraId;                break;            }        } catch (CameraAccessException e) {            e.printStackTrace();        }    }

//选择sizeMap中大于并且最接近width和height的size    private Size getOptimalSize(Size[] sizeMap, int width, int height) {        List
     
       sizeList = new ArrayList<>();        for (Size option : sizeMap) {            if (width > height) {                if (option.getWidth() > width && option.getHeight() > height) {                    sizeList.add(option);                }            } else {                if (option.getWidth() > height && option.getHeight() > width) {                    sizeList.add(option);                }            }        }        if (sizeList.size() > 0) {            return Collections.min(sizeList, new Comparator
      
       () {                @Override                public int compare(Size lhs, Size rhs) {                    return Long.signum(lhs.getWidth() * lhs.getHeight() - rhs.getWidth() * rhs.getHeight());                }            });        }        return sizeMap[0];    }

private void setupImageReader() {        //2代表ImageReader中最多可以获取两帧图像流        mImageReader = ImageReader.newInstance(mCaptureSize.getWidth(), mCaptureSize.getHeight(),                ImageFormat.JPEG, 1);        mImageReader.setOnImageAvailableListener(new ImageReader.OnImageAvailableListener() {            @Override            public void onImageAvailable(ImageReader reader) {                final Image image = reader.acquireNextImage();                mCameraHandler.post(new imageSaver(image));                getActivity().runOnUiThread(new Runnable() {                    @Override                    public void run() {                        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) {                            ivShow.setImageBitmap(bitmap);                        }                    }                });            }        }, mCameraHandler);    }

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.capacity()];            buffer.get(data);            String path = Environment.getExternalStorageDirectory() + "/DCIM/361camera/";            File mImageFile = new File(path);            if (!mImageFile.exists()) {                boolean ret = mImageFile.mkdirs();                assert (ret);            }            String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());            String fileName = path + "IMG_" + timeStamp + ".jpg";            FileOutputStream fos = null;            try {                fos = new FileOutputStream(fileName);                fos.write(data, 0, data.length);            } catch (IOException e) {                e.printStackTrace();            } finally {                if (fos != null) {                    try {                        fos.close();                    } catch (IOException e) {                        e.printStackTrace();                    }                }                mImage.close();            }        }    }

3，开启相机

private void openCamera() {        mCameraManager = (CameraManager) getContext().getSystemService(Context.CAMERA_SERVICE);        try {            if (ActivityCompat.checkSelfPermission(getContext(), Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {                //申请WRITE_EXTERNAL_STORAGE权限                requestPermissions(new String[]{Manifest.permission.CAMERA},                        REQUEST_CAMERA_CODE);                //return;            } else {                mCameraManager.openCamera(mCameraId, mStateCallback, mCameraHandler);            }        } 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 CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {        @Override        public void onOpened(CameraDevice camera) {            mCameraDevice = camera;            startPreview();        }        @Override        public void onDisconnected(CameraDevice camera) {            camera.close();            mCameraDevice = null;        }        @Override        public void onError(CameraDevice camera, int error) {            camera.close();            mCameraDevice = null;        }    };

4，开启相机预览

private void startPreview() {        SurfaceTexture mSurfaceTexture = mTextureView.getSurfaceTexture();        mSurfaceTexture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());        Surface previewSurface = new Surface(mSurfaceTexture);        try {            mCaptureRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);            mCaptureRequestBuilder.addTarget(previewSurface);            mCameraDevice.createCaptureSession(Arrays.asList(previewSurface, mImageReader.getSurface()), new CameraCaptureSession.StateCallback() {                @Override                public void onConfigured(CameraCaptureSession session) {                    try {                        mCaptureRequest = mCaptureRequestBuilder.build();                        mCameraCaptureSession = session;                        mCameraCaptureSession.setRepeatingRequest(mCaptureRequest, null, mCameraHandler);                    } catch (CameraAccessException e) {                        e.printStackTrace();                    }                }                @Override                public void onConfigureFailed(CameraCaptureSession session) {                }            }, mCameraHandler);        } catch (CameraAccessException e) {            e.printStackTrace();        }    }

5，实现PreviewCallback

首先创建一个ImageReader，并监听它的事件（见上面的代码setupImageReader()）。然后开启预览之前，设置ImageReader为输出Surface（见上面setupCamera()的代码）。

6，拍照

public void takePicture() {        lockFocus();    }    private void lockFocus() {        try {            mCaptureRequestBuilder.set(CaptureRequest.CONTROL_AF_TRIGGER, CameraMetadata.CONTROL_AF_TRIGGER_START);            mCameraCaptureSession.capture(mCaptureRequestBuilder.build(), mCaptureCallback, mCameraHandler);        } catch (CameraAccessException e) {            e.printStackTrace();        }    }

源代码地址：https://github.com/gengqifu/361Camera。欢迎顺手star一下~~~