Android — Camera聚焦流程

原文  http://www.cnphp6.com/archives/65098

主题 Android

Camera.java                                                                          

• autoFocus()聚焦回调函数

@Override
  public void autoFocus() {
    //记录当前聚焦开始时间
    mFocusStartTime = System.currentTimeMillis();
    //设置Camera的回调聚焦
    mCameraDevice.autoFocus(mAutoFocusCallback);
    //设置Camera的状态为Focusing
    setCameraState(FOCUSING);
  }

• 设置相机状态

private void setCameraState(int state) {
    mCameraState = state;
    switch (state) {
      case SNAPSHOT_IN_PROGRESS:
      case FOCUSING:
        enableCameraControls(false);
        break;
      case IDLE:
      case PREVIEW_STOPPED:
        enableCameraControls(true);
        break;
    }
  }

• enableCameraControls，设置enable，是否可以点击

/**
   * 设置几个button或者view不可点击
   * @param enable
   */
  private void enableCameraControls(boolean enable) {
    if (mIndicatorControlContainer != null) {
      mIndicatorControlContainer.setEnabled(enable);
    }
    if (mModePicker != null) mModePicker.setEnabled(enable);
    if (mZoomControl != null) mZoomControl.setEnabled(enable);
    if (mThumbnailView != null) mThumbnailView.setEnabled(enable);
  }

• mIndicatorControlContainer的enable的设置

Override
  public void setEnabled(boolean enabled) {
    super.setEnabled(enabled);
    final int count = getChildCount();
    for (int i = 0; i < count; i++) {
      View v = getChildAt(i);
      // Zoom buttons and shutter button are controlled by the activity.
      if (v instanceof AbstractIndicatorButton) {
        v.setEnabled(enabled);
        // Show or hide the indicator buttons during recording.
        if (mCurrentMode == MODE_VIDEO) {
          v.setVisibility(enabled ? View.VISIBLE : View.INVISIBLE);
        }
      }
    }
    if (mCameraPicker != null) {
      mCameraPicker.setEnabled(enabled);
      if (mCurrentMode == MODE_VIDEO) {
        mCameraPicker.setVisibility(enabled ? View.VISIBLE : View.INVISIBLE);
      }
    }
  }

• mAutoFocusCallback中的处理

private final class AutoFocusCallback
      implements android.hardware.Camera.AutoFocusCallback {
  public void onAutoFocus(
    boolean focused, android.hardware.Camera camera) {
      //如果是暂停状态，不聚焦
      if (mPausing) return;
      //算出当前到聚焦开始的时间差
      mAutoFocusTime = System.currentTimeMillis() - mFocusStartTime;
      Log.v(TAG, "mAutoFocusTime = " + mAutoFocusTime + "ms");
      //设置Camera状态为
      setCameraState(IDLE);
      //调用FocusManager中的AutoFocus
      mFocusManager.onAutoFocus(focused);
  }
    }

FocusManager.java                                                                  

/**
   * 聚焦
   * @param focused
   */
  public void onAutoFocus(boolean focused) {
    Log.i(TAG, "focus used : " + (System.currentTimeMillis() - focusStart));
    //正在进行聚焦，拍照动作必须再聚焦完之后
    if (mState == STATE_FOCUSING_SNAP_ON_FINISH) {
      // 无论聚焦成功还是失败，都会拍照。如果要进行拍照发声，就无需AF发声了
      if (focused) {
        //聚焦成功
        mState = STATE_SUCCESS;
      } else {
        //聚焦失败
        mState = STATE_FAIL;
      }
      //更新聚焦框UI&&设置人脸识别UI已经各种状态的设置
      updateFocusUI();
      //拍照，mState的状态变为STATE_IDLE
      capture();
    } else if (mState == STATE_FOCUSING) {//如果是聚焦中的状态
      //此状态的发生分为两种，half-pressing按压聚焦或者触摸聚焦被触发，这个时候不要发生拍照动作
      if (focused) {
        //聚焦成功
        mState = STATE_SUCCESS;
        //在连续聚焦状态不要发声，聚焦回调会在拍照前完成，所有状态一直为STATE_FOCUSING
        if (!Parameters.FOCUS_MODE_CONTINUOUS_PICTURE.
            equals(mFocusMode)) {
          mListener.playSound(CameraSound.FOCUS_COMPLETE);
        }
      } else {
        //聚焦失败
        mState = STATE_FAIL;
      }
      //更新聚焦&&人脸UI
      updateFocusUI();
      // If this is triggered by touch focus, cancel focus after a
      // while.
      //如果是触摸聚焦，需要延迟一下取消掉聚焦
      if (mFocusArea != null) {
        mHandler.sendEmptyMessageDelayed(RESET_TOUCH_FOCUS, RESET_TOUCH_FOCUS_DELAY);
      }
    } else if (mState == STATE_IDLE) {//空闲
      // User has released the focus key before focus completes.
      // Do nothing.
    }
  }

• 处理消息

private class MainHandler extends Handler {
    @Override
    public void handleMessage(Message msg) {
      switch (msg.what) {
        case RESET_TOUCH_FOCUS: {
          //取消掉聚焦
          cancelAutoFocus();
          //开始人脸识别
          mListener.startFaceDetection();
          break;
        }
      }
    }
  }

/**
     * 再重置tap area之前调用mListener.cancelAutofocus，否则，聚焦模式将一直是自动&tap聚焦，并且驱动也不会重置
     */
    private void cancelAutoFocus() {
  //放置聚焦框到屏幕中间
  resetTouchFocus();
  mListener.cancelAutoFocus();
  if (mFaceView != null) mFaceView.resume();
  mState = STATE_IDLE;
  updateFocusUI();
  mHandler.removeMessages(RESET_TOUCH_FOCUS);
    }

• 触摸聚焦

/**
     * 触摸，，这里会发生触摸聚焦
     * @param e
     * @return
     */
    public boolean onTouch(MotionEvent e) {
  //没有初始化或者拍照前的聚焦的状态，直接返回
  if (!mInitialized || mState == STATE_FOCUSING_SNAP_ON_FINISH) return false;

  //让用户可以取消掉之前未消失的触摸聚焦
  if ((mFocusArea != null) && (mState == STATE_FOCUSING ||
        mState == STATE_SUCCESS || mState == STATE_FAIL)) {
      cancelAutoFocus();
  }

  // Initialize variables.
  int x = Math.round(e.getX());
  int y = Math.round(e.getY());
  int focusWidth = mFocusIndicatorRotateLayout.getWidth();
  int focusHeight = mFocusIndicatorRotateLayout.getHeight();
  int previewWidth = mPreviewFrame.getWidth();
  int previewHeight = mPreviewFrame.getHeight();
  if (mFocusArea == null) {
      mFocusArea = new ArrayList<Area>();
      mFocusArea.add(new Area(new Rect(), 1));
      mMeteringArea = new ArrayList<Area>();
      mMeteringArea.add(new Area(new Rect(), 1));
  }

  //将坐标转换为驱动的格式。AE面积更大,因为曝光会敏感和容易，或者说曝光不足,如果面积太小了。
  calculateTapArea(focusWidth, focusHeight, 1f, x, y, previewWidth, previewHeight,
    mFocusArea.get(0).rect);
  calculateTapArea(focusWidth, focusHeight, 1.5f, x, y, previewWidth, previewHeight,
    mMeteringArea.get(0).rect);

  // Use margin to set the focus indicator to the touched area.
  RelativeLayout.LayoutParams p =
    (RelativeLayout.LayoutParams) mFocusIndicatorRotateLayout.getLayoutParams();
  int left = Util.clamp(x - focusWidth / 2, 0, previewWidth - focusWidth);
  int top = Util.clamp(y - focusHeight / 2, 0, previewHeight - focusHeight);
  p.setMargins(left, top, 0, 0);
  // Disable "center" rule because we no longer want to put it in the center.
  int[] rules = p.getRules();
  rules[RelativeLayout.CENTER_IN_PARENT] = 0;
  mFocusIndicatorRotateLayout.requestLayout();

  //停止人脸识别，因为要进行识别聚焦和测量area
  mListener.stopFaceDetection();

  //设置聚焦区域&测量区域
  mListener.setFocusParameters();
  //如果支持触摸聚焦&&手指抬起
  if (mFocusAreaSupported && (e.getAction() == MotionEvent.ACTION_UP)) {
      autoFocus();
  } else {  // Just show the indicator in all other cases.
      updateFocusUI();
      // Reset the metering area in 3 seconds.
      mHandler.removeMessages(RESET_TOUCH_FOCUS);
      mHandler.sendEmptyMessageDelayed(RESET_TOUCH_FOCUS, RESET_TOUCH_FOCUS_DELAY);
  }

  return true;
    }

聚焦各个状态能做什么事不能做什么事&切换                                       

• STATE_IDLE

doSnap()：空闲状态可以执行拍照
onAutoFocus(boolean focused)：用户再聚焦完成前放掉了聚焦按钮，所以不做任何事。
onPreviewStarted()，onPreviewStopped()：状态都变为空闲
cancelAutoFocus()：取消聚焦，状态变为空闲
updateFocusUI()：如果空闲&有聚焦区域，显示聚焦框框

• STATE_FOCUSING

onShutterUp()：如果是focusmode为自动聚焦，状态为正在聚焦，则取消掉聚焦
doSnap()：如果是正在聚焦状态，将状态改为聚焦完拍照状态
onAutoFocus(boolean focused)：判断focused，为true变为聚焦成功状态，为false变为聚焦失败状态
onTouch(MotionEvent e)：如果正在聚焦&之前有手动聚焦了，则取消掉之前的聚焦
autoFocus()：状态变为聚焦状态
updateFocusUI()：显示聚焦的框框

• STATE_FOCUSING_SNAP_ON_FINISH

onShutterUp()：状态不是聚焦完拍照，可以设置FocusParameters
onAutoFocus(boolean focused)：判断focused，为true变为聚焦成功状态，为false变为聚焦失败状态，更新聚焦框UI
onTouch(MotionEvent e)：直接不继续操作下去
updateFocusUI()：显示聚焦的框框

• STATE_SUCCESS

onShutterDown()：如果是自动聚焦mode，并且不为聚焦成功状态，执行聚焦
onShutterUp()： 如果是自动聚焦mode，并且为聚焦成功状态，执行取消聚焦
doSnap()：拍照
onTouch(MotionEvent e)：让用户可以取消掉之前未消失的触摸聚焦
updateFocusUI()：聚焦框框显示成功

• STATE_FAIL

onShutterDown()：如果是自动聚焦mode，并且不为聚焦失败状态，执行聚焦
onShutterUp()： 如果是自动聚焦mode，并且为聚焦失败状态，执行取消聚焦
doSnap()：拍照
onTouch(MotionEvent e)：让用户可以取消掉之前未消失的触摸聚焦
updateFocusUI()：聚焦框框显示失败