一、切換攝像頭

在前後攝像頭之間切換，首先需要關閉之前開啟的攝像頭，關閉preview，之後重新開啟新的攝像頭，重新開啟preview。

public void switchCamera() {
        if (mCameraId.equals(CAMERA_FRONT)) {
            mCameraId = CAMERA_BACK;
            closeCamera();
            reopenCamera();

        } else if (mCameraId.equals(CAMERA_BACK)) {
            mCameraId = CAMERA_FRONT;
            closeCamera();
            reopenCamera();
        }
    }

關閉攝像頭：

/**
     * Closes the current {@link CameraDevice}.
     */
    private void closeCamera() {
        try {
            mCameraOpenCloseLock.acquire();
            synchronized (mCameraStateLock) {

                // Reset state and clean up resources used by the camera.
                // Note: After calling this, the ImageReaders will be closed after any background
                // tasks saving Images from these readers have been completed.
                mPendingUserCaptures = 0;
                mState = STATE_CLOSED;
                if (null != mCaptureSession) {
                    mCaptureSession.close();
                    mCaptureSession = null;
                }
                if (null != mCameraDevice) {
                    mCameraDevice.close();
                    mCameraDevice = null;
                }
                if (null != mJpegImageReader) {
                    mJpegImageReader.close();
                    mJpegImageReader = null;
                }
                if (null != mRawImageReader) {
                    mRawImageReader.close();
                    mRawImageReader = null;
                }
            }
        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted while trying to lock camera closing.", e);
        } finally {
            mCameraOpenCloseLock.release();
        }
    }

開啟新的攝像頭：

public void reopenCamera() {
        if (mTextureView.isAvailable()) {
            openCamera();
        } else {
            mTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
        }
    }

如果TextureView是available的，那麼直接呼叫openCamera（）開啟camera（openCamera()的程式碼參考之前的部落格）；如果|TextureView是unavailable的，那麼呼叫TextureView的setSurfaceTextureListener設定SurfaceTextureListener（參考上一篇部落格）。

二、延時拍攝

要實現延時拍攝，核心是實現一個定時器。本例延時分為三種模式：3s延時，10s按時，無延時。可以在三種模式之中自有切換。

private void switchDelayState() {
        switch (mDelayState) {
            case 0:
                mTimer.setImageResource(R.mipmap.ic_3s);
                mDelayTime = 3 * 1000;
                mDelayState = 1;
                break;
            case 1:
                mTimer.setImageResource(R.mipmap.ic_10s);
                mDelayTime = 10 * 1000;
                mDelayState = 2;
                break;
            case 2:
                mTimer.setImageResource(R.mipmap.timer);
                mDelayTime = 0;
                mDelayState = 0;
                break;
            default:
                break;
        }
    }

變數mDelayTime和mDelaySate的定義：

/*
     * Delay state, 0 represents no delay, 1 represents 3s delay, while 2 represents 10s delay
     */
    private short mDelayState = 0; // Timer
    private short mDelayTime;

當拍攝按鈕被點選時：

@Override
    public void onClick(View view) {
        switch (view.getId()) {
            case R.id.capture: {
                if (mDelayState == 0) {
                    takePicture();
                } else {
                    new CountDownTimer(mDelayTime, TIME_INTERVAL) {
                        @Override
                        public void onTick(long millisUntilFinished) {
                            mTimeText.setVisibility(View.VISIBLE);
                            mTimeText.setText("" + millisUntilFinished / TIME_INTERVAL);
                        }

                        @Override
                        public void onFinish() {
                            mTimeText.setVisibility(View.GONE);
                            takePicture();
                        }
                    }.start();
                }
                break;
            }

但有3s或10s延時的時候，利用CountDownTimer實現倒數計時並每隔一秒更新剩餘時間提示，到時候執行拍照功能。

三、切換閃光模式

支援自動，強制，禁止閃光。與閃光模式有關的屬性是CaptureRequest.CONTROL_AE_MODE和CaptureRequest.FLASH_MODE。 如果要使用FLASH_MODE屬相，閃光燈必須可用，並且，CONTROL_AE_MODE必須設定為on或off，否則，自動曝光屬性的ON_AUTO_FLASH,ON_ALWAYS_FLASH,
ON_AUTO_FLASH_REDEYE將會覆蓋FLASH_MODE的設定。

private void switchFlashMode() {
        switch (mFlashMode) {
            case 0:
                mFlashMode = 1;
                mFlashBtn.setImageResource(R.mipmap.flash_auto);
                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
                try {
                    mCaptureSession.setRepeatingRequest(
                            mPreviewRequestBuilder.build(),
                            mPreCaptureCallback, mBackgroundHandler);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                    return;
                }

                break;
            case 1:
                mFlashMode = 2;
                mFlashBtn.setImageResource(R.mipmap.flash_on);
                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
                try {
                    mCaptureSession.setRepeatingRequest(
                            mPreviewRequestBuilder.build(),
                            mPreCaptureCallback, mBackgroundHandler);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                    return;
                }
                break;
            case 2:
                mFlashMode = 0;
                mFlashBtn.setImageResource(R.mipmap.flash_off);
                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON);
                mPreviewRequestBuilder.set(CaptureRequest.FLASH_MODE, CaptureRequest.FLASH_MODE_OFF);
                try {
                    mCaptureSession.setRepeatingRequest(
                            mPreviewRequestBuilder.build(),
                            mPreCaptureCallback, mBackgroundHandler);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                    return;
                }
                break;
        }
    }

在takePicture（）之前，需要再次設定：

private void setFlashMode() {
        switch (mFlashMode) {
            case 0:
                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON);
                mPreviewRequestBuilder.set(CaptureRequest.FLASH_MODE, CaptureRequest.FLASH_MODE_OFF);
                break;
            case 1:
                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
                break;
            case 2:
                mPreviewRequestBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_ALWAYS_FLASH);
                break;
        }
    }

程式碼參考：https://github.com/gengqifu/361Camera，歡迎fork/star。