上一篇文章简单的写了一点调用系统摄像头录制视频和使用原生videoView播放视频的方法。那么这篇文章继续完成未完成的作业。

使用SurfaceView实现镜头的预览

布局文件只需要一个SurfaceView

<SurfaceView
        android:id="@+id/surface_view"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent" />

Activity实现回调方法

implements SurfaceHolder.Callback

注册回调

@BindView(R.id.surface_view)
SurfaceView mSurfaceView;//预览窗口
Camera camera;
//baseActivity中的方法，也可以直接写在onCreate()中
   @Override
    protected void initView() {
        mSurfaceView.getHolder().addCallback(this);
    }

在创建的回调中去开启镜头的预览

 @Override
    public void surfaceCreated(SurfaceHolder holder) {
        camera = Camera.open(BACK);
        camera.setDisplayOrientation(90);
        try {
            camera.setPreviewDisplay(holder);
            camera.startPreview();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

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

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        camera.release();
    }

使用TextureView去开启镜头浏览

首先还是定义TextureView 和Camera

TextureView textureView;
Camera camera;

定义一个TextureView.SurfaceTextureListener,并在此处开启预览

  private class MySurfaceTextureViewListener implements TextureView.SurfaceTextureListener {

        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
            try {
                  camera.setPreviewTexture(surfaceTexture);
                  camera.startPreview();
                  } catch (IOException e) {
                        e.printStackTrace();
                          }
        }

        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
           
        }

        @Override
        public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
            surface.release();
            camera.setPreviewCallback(null);
            camera.stopPreview();
            camera.release();
            camera = null;
            return false;
        }

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture surface) {

        }
    }

初始化布局并且设置监听器，打开Camera

   //baseActivity中的方法，也可以直接写在onCreate()中
   @Override
    protected void initView() {
        textureView.setSurfaceTextureListener(new MySurfaceTextureViewListener());
        camera = Camera.open();
        camera.setDisplayOrientation(90);
    }

切换前后摄像头

可能写得很复杂，见谅

private static final int FRONT = 1;//前置摄像头标记
private static final int BACK = 0;//后置摄像头标记
private int currentCameraType = BACK;//当前打开的摄像头标记

private void changeCamera() throws IOException{
        //切换前后摄像头
        int cameraCount = 0;
        Camera.CameraInfo cameraInfo = new Camera.CameraInfo();
        cameraCount = Camera.getNumberOfCameras();//得到摄像头的个数

        for(int i = 0; i < cameraCount; i++   ) {
            Camera.getCameraInfo(i, cameraInfo);//得到每一个摄像头的信息
            if(currentCameraType == BACK) {
                //现在是后置，变更为前置
                if(cameraInfo.facing  == Camera.CameraInfo.CAMERA_FACING_FRONT) {//代表摄像头的方位，CAMERA_FACING_FRONT前置      CAMERA_FACING_BACK后置
                    camera.stopPreview();//停掉原来摄像头的预览
                    camera.release();//释放资源
                    camera = null;//取消原来摄像头
                    camera = Camera.open(i);//打开当前选中的摄像头
                    camera.setDisplayOrientation(90);
                    try {
                        camera.setPreviewDisplay(mSurfaceView.getHolder());//通过surfaceview显示取景画面
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    camera.startPreview();//开始预览
                    currentCameraType = FRONT;
                    break;
                }
            } else {
                //现在是前置， 变更为后置
                if(cameraInfo.facing  == Camera.CameraInfo.CAMERA_FACING_BACK) {//代表摄像头的方位，CAMERA_FACING_FRONT前置      CAMERA_FACING_BACK后置
                    camera.stopPreview();//停掉原来摄像头的预览
                    camera.release();//释放资源
                    camera = null;//取消原来摄像头
                    camera = Camera.open(i);//打开当前选中的摄像头
                    camera.setDisplayOrientation(90);
                    try {
                        camera.setPreviewDisplay(mSurfaceView.getHolder());//通过surfaceview显示取景画面
                    } catch (IOException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    camera.startPreview();//开始预览
                    currentCameraType = BACK;
                    break;
                }
            }

        }
    }

取到NV21的回调

Android 中Google支持的 Camera Preview Callback的YUV常用格式有两种：一个是NV21，一个是YV12。Android一般默认使用YCbCr_420_SP的格式（NV21）。

配置回调格式

Camera.Parameters parameters = camera.getParameters();
parameters.setPreviewFormat(ImageFormat.NV21);
camera.setParameters(parameters);

在 Camera 在 release 之前设置 PreviewCallback 即可，bytes的数据就是NV21回调数据

camera.setPreviewCallback(new Camera.PreviewCallback() {
                    @Override
                    public void onPreviewFrame(byte[] bytes, Camera camera) {
                        
                    }
                });