使用Camera进行拍照 & 后台静默拍照的代码

使用Camera进行拍照的代码：

public class CameraActivity extends AppCompatActivity implements SurfaceHolder.Callback {

    private static final String TAG = "CameraActivity";

    private Camera mCamera;
    private SurfaceView mSurfaceView;
    private SurfaceHolder mSurfaceHolder;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera);

        mSurfaceView = findViewById(R.id.surface_view);
        mSurfaceHolder = mSurfaceView.getHolder();
        mSurfaceHolder.addCallback(this);
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mCamera = Camera.open();
        try {
            mCamera.setPreviewDisplay(holder);
        } catch (IOException e) {
            Log.e(TAG, "Error setting preview display", e);
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        mCamera.startPreview();
        mCamera.setPreviewCallback(new Camera.PreviewCallback() {
            @Override
            public void onPreviewFrame(byte[] data, Camera camera) {
                // 判断是否需要拍照
                if (needTakePicture()) {
                    // 拍照
                    mCamera.takePicture(null, null, mPictureCallback);
                }
            }
        });
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }

    private Camera.PictureCallback mPictureCallback = new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            // 保存照片到指定目录
            savePicture(data);
            camera.startPreview();
        }
    };

    private boolean needTakePicture() {
        // 判断是否需要拍照的逻辑
        return false;
    }

    private void savePicture(byte[] data) {
        // 保存照片到指定目录的逻辑
    }
}

后台静默拍照的代码：

public class CameraService extends Service implements SurfaceHolder.Callback {

    private static final String TAG = "CameraService";

    private Camera mCamera;
    private SurfaceHolder mSurfaceHolder;

    @Override
    public void onCreate() {
        super.onCreate();

        // 初始化SurfaceHolder
        SurfaceView surfaceView = new SurfaceView(this);
        WindowManager.LayoutParams layoutParams = new WindowManager.LayoutParams(
                1, 1,
                WindowManager.LayoutParams.TYPE_SYSTEM_OVERLAY,
                WindowManager.LayoutParams.FLAG_WATCH_OUTSIDE_TOUCH,
                PixelFormat.TRANSLUCENT
        );
        WindowManager windowManager = (WindowManager) getSystemService(Context.WINDOW_SERVICE);
        windowManager.addView(surfaceView, layoutParams);
        mSurfaceHolder = surfaceView.getHolder();
        mSurfaceHolder.addCallback(this);
    }

    @Override
    public void onDestroy() {
        super.onDestroy();
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }

    @Nullable
    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        mCamera = Camera.open();
        try {
            mCamera.setPreviewDisplay(holder);
        } catch (IOException e) {
            Log.e(TAG, "Error setting preview display", e);
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        mCamera.startPreview();
        mCamera.setPreviewCallback(new Camera.PreviewCallback() {
            @Override
            public void onPreviewFrame(byte[] data, Camera camera) {
                // 判断是否需要拍照
                if (needTakePicture()) {
                    // 拍照
                    mCamera.takePicture(null, null, mPictureCallback);
                }
            }
        });
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
    }

    private Camera.PictureCallback mPictureCallback = new Camera.PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            // 保存照片到指定目录
            savePicture(data);
            camera.startPreview();
        }
    };

    private boolean needTakePicture() {
        // 判断是否需要拍照的逻辑
        return false;
    }

    private void savePicture(byte[] data) {
        // 保存照片到指定目录的逻辑
    }
}

需要注意的是，在使用后台静默拍照的方法时，需要在AndroidManifest.xml文件中添加以下权限：

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW"/>