访问相机

获取 Camera 对象的实例是直接控制相机流程的第一步. 打开建议在子线程中操作.

private boolean safeCameraOpen(private boolean safeCameraOpen(int id) {
    boolean qOpened = false;

    try {
        releaseCameraAndPreview();
        camera = Camera.open(id);
        qOpened = (camera != null);
    } catch (Exception e) {
        Log.e(getString(R.string.app_name), "failed to open Camera");
        e.printStackTrace();
    }

    return qOpened;
}

private void releaseCameraAndPreview() {
    preview.setCamera(null);
    if (camera != null) {
        camera.release();
        camera = null;
    }
}

检查相机功能

使用 Camera.getParameters() 方法获取有关相机功能的详细信息

使用 Camera.getCameraInfo() 确定设备的摄像头是前置还是后置，以及图像的屏幕方向

创建预览类

相机预览类是一个 SurfaceView，可以显示来自相机的实时图像数据.

以下示例代码演示如何创建可包含在 View 布局中的基础相机预览类。此类实现 SurfaceHolder.Callback，以便捕获用于创建和销毁视图的回调事件，这些是分配相机预览输入的必需事件。

/** 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());
        }
    }
}

在布局中放置预览

surfaceview可以添加到framelayout中

可使用 setDisplayOrientation() 方法设置预览图像的旋转。为了在用户重定向手机时改变预览屏幕方向，请在您预览类的 surfaceChanged() 方法中，首先使用 Camera.stopPreview() 停止预览并更改屏幕方向，然后使用 Camera.startPreview() 重新启动预览。

用完相机后，请记得通过调用 Camera.release() 来释放 Camera 对象