com.android.camera.Camera.java，主要的实现Activity，继承于ActivityBase。
ActivityBase
在ActivityBase中执行流程：
- onCreate中进行判断是否是平板；
- onResume中判断是否锁屏，锁屏&camera不存在时候，mOnResumePending置为true，否则置为false并执行doOnResume；
- onWindowFocusChanged中判断是否获取到焦点&mOnResumePending，满足的话执行doOnResume；
- onPause中将mOnResumePending置为false；
Camera.java
接下来分析Camera.java，执行流程：
1、onCreate
// 获得摄像头的数量，前置和后置
getPreferredCameraId();
// 获得对焦设置eg：连续对焦或者其它
String[] defaultFocusModes = getResources().getStringArray(R.array.pref_camera_focusmode_default_array);
//实例化Focus管理对象
mFocusManager = new FocusManager(mPreferences, defaultFocusModes);
// 开启线程来启动摄像头
mCameraOpenThread.start();
// 是否是第三方应用启动拍照功能
mIsImageCaptureIntent = isImageCaptureIntent();
// 设置UI布局文件
setContentView(R.layout.camera);
if (mIsImageCaptureIntent) {
// 当第三方其送拍照，需要显示不同的UI，比如取消键盘
mReviewDoneButton = (Rotatable) findViewById(R.id.btn_done);
mReviewCancelButton = (Rotatable) findViewById(R.id.btn_cancel);
findViewById(R.id.btn_cancel).setVisibility(View.VISIBLE);
} else {
// 反之显示缩略图
mThumbnailView = (RotateImageView) findViewById(R.id.thumbnail);
mThumbnailView.enableFilter(false);
mThumbnailView.setVisibility(View.VISIBLE);
}
// 一个能旋转的dialog.比如相机设置的dialog,这个类实现了旋转的父类
mRotateDialog = new RotateDialogController(this, R.layout.rotate_dialog);
// 设置camera的ID，写道SharedPreference中
mPreferences.setLocalId(this, mCameraId);
// 更新preference
CameraSettings.upgradeLocalPreferences(mPreferences.getLocal());
// 获得相机数
mNumberOfCameras = CameraHolder.instance().getNumberOfCameras();
// 貌似是获得是否是快速拍照
mQuickCapture = getIntent().getBooleanExtra(EXTRA_QUICK_CAPTURE, false);
// 为当前的preview重置曝光值
resetExposureCompensation();
// 隐藏系统导航栏等
Util.enterLightsOutMode(getWindow());
//SurfaceView
SurfaceView preview = (SurfaceView) findViewById(R.id.camera_preview);
SurfaceHolder holder = preview.getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
try {
// 这个join语句就是为了保证openCamera的线程执行完后，当前的线程才开始运行。主要是为了确保camera设备被打开了
mCameraOpenThread.join();
// 线程执行完后置为空来让系统回收资源
mCameraOpenThread = null;
if (mOpenCameraFail) {
// 打开camera失败，显示“无法连接到相机”
Util.showErrorAndFinish(this, R.string.cannot_connect_camera);
return;
} else if (mCameraDisabled) {
// 由于安全政策限制，相机已被停用
Util.showErrorAndFinish(this, R.string.camera_disabled);
return;
}
} catch (InterruptedException ex) {
// ignore
}
//开启显示的子线程
mCameraPreviewThread.start();
if (mIsImageCaptureIntent) {
//如果是第三方开启的 ，setupCaptureParams 设置拍照的参数
setupCaptureParams();
} else {
//设置ModePicker
mModePicker = (ModePicker) findViewById(R.id.mode_picker);
mModePicker.setVisibility(View.VISIBLE);
mModePicker.setOnModeChangeListener(this);
mModePicker.setCurrentMode(ModePicker.MODE_CAMERA);
}
mZoomControl = (ZoomControl) findViewById(R.id.zoom_control);
mOnScreenIndicators = (Rotatable) findViewById(R.id.on_screen_indicators);
mLocationManager = new LocationManager(this, this);
//摄像头ID
mBackCameraId = CameraHolder.instance().getBackCameraId();
mFrontCameraId = CameraHolder.instance().getFrontCameraId();
// 在startPreview里面有notify方法
synchronized (mCameraPreviewThread) {
try {
mCameraPreviewThread.wait();
} catch (InterruptedException ex) {
// ignore
}
}
// 初始化各种控制按钮
initializeIndicatorControl();
//初始化拍照声音
mCameraSound = new CameraSound();
try {
//确保显示
mCameraPreviewThread.join();
} catch (InterruptedException ex) {
// ignore
}
mCameraPreviewThread = null;
2、surfaceCreated
啥都没做
3、surfaceChanged
// 确保在holder中有surface
if (holder.getSurface() == null) {
Log.d(TAG, "holder.getSurface() == null");
return;
}
// We need to save the holder for later use, even when the mCameraDevice
// is null. This could happen if onResume() is invoked after this
// function.
mSurfaceHolder = holder;
if (mCameraDevice == null) return;
if (mPausing || isFinishing()) return;
// Set preview display if the surface is being created. Preview was
// already started. Also restart the preview if display rotation has
// changed. Sometimes this happens when the device is held in portrait
// and camera app is opened. Rotation animation takes some time and
// display rotation in onCreate may not be what we want.
if (mCameraState == PREVIEW_STOPPED) {
startPreview();
startFaceDetection();
} else {
if (Util.getDisplayRotation(this) != mDisplayRotation) {
setDisplayOrientation();
}
if (holder.isCreating()) {
// Set preview display if the surface is being created and preview
// was already started. That means preview display was set to null
// and we need to set it now.
setPreviewDisplay(holder);
}
}
// If first time initialization is not finished, send a message to do
// it later. We want to finish surfaceChanged as soon as possible to let
// user see preview first.
if (!mFirstTimeInitialized) {
mHandler.sendEmptyMessage(FIRST_TIME_INIT);
} else {
initializeSecondTime();
}
如果是第一次加载，则执行mHandler.sendEmptyMessage(FIRST_TIME_INIT); 对应处理的是initializeFirstTime();
/**
* 初始化，第一次初始化
* // Snapshots can only be taken after this is called. It should be called
* // once only. We could have done these things in onCreate() but we want to
* // make preview screen appear as soon as possible.
*/
private void initializeFirstTime() {
if (mFirstTimeInitialized) return; // Create orientation listenter. This should be done first because it
// takes some time to get first orientation.
mOrientationListener = new MyOrientationEventListener(Camera.this);
mOrientationListener.enable(); // Initialize location sevice.
boolean recordLocation = RecordLocationPreference.get(
mPreferences, getContentResolver());
// 初始化屏幕最上方的标志，比如开启了曝光值啊，什么的
initOnScreenIndicator();
// 位置服务
mLocationManager.recordLocation(recordLocation); keepMediaProviderInstance();
// 检查存储空间和初始化储存目录
checkStorage();
// Initialize last picture button.
mContentResolver = getContentResolver();
if (!mIsImageCaptureIntent) { // no thumbnail in image capture intent
// 初始化缩略图
initThumbnailButton();
}
// Initialize shutter button.
// 初始化拍照按钮并设置监听事件
mShutterButton = (ShutterButton) findViewById(R.id.shutter_button);
mShutterButton.setOnShutterButtonListener(this);
mShutterButton.setVisibility(View.VISIBLE);
// Initialize focus UI.
mPreviewFrame = findViewById(R.id.camera_preview);
mPreviewFrame.setOnTouchListener(this);
// 聚焦框
mFocusAreaIndicator = (RotateLayout) findViewById(R.id.focus_indicator_rotate_layout);
CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];
boolean mirror = (info.facing == CameraInfo.CAMERA_FACING_FRONT);
mFocusManager.initialize(mFocusAreaIndicator, mPreviewFrame, mFaceView, this,
mirror, mDisplayOrientation);
// 初始化一个图片的保存线程
mImageSaver = new ImageSaver();
// 设置屏幕亮度
Util.initializeScreenBrightness(getWindow(), getContentResolver());
// 注册SD卡相关的广播，比如拔出存储卡什么的
installIntentFilter();
// 初始化缩放UI
initializeZoom();
// 更新屏幕上的闪光灯什么的标记
updateOnScreenIndicators();
// 开始面部检测
startFaceDetection();
// Show the tap to focus toast if this is the first start.
// 假如是第一次启动，提示用户“触摸对焦”
if (mFocusAreaSupported &&
mPreferences.getBoolean(CameraSettings.KEY_CAMERA_FIRST_USE_HINT_SHOWN, true)) {
// Delay the toast for one second to wait for orientation.
mHandler.sendEmptyMessageDelayed(SHOW_TAP_TO_FOCUS_TOAST, 1000);
}
mFirstTimeInitialized = true;
addIdleHandler();
}
如果不是，则执行initializeSecondTime();
/**
* // If the activity is paused and resumed, this method will be called in
* // onResume.
*/
private void initializeSecondTime() {
// Start orientation listener as soon as possible because it takes
// some time to get first orientation.
//方向翻转设置enable，其中包括翻转的时候的动画
mOrientationListener.enable(); // Start location update if needed.
boolean recordLocation = RecordLocationPreference.get(
mPreferences, getContentResolver());
mLocationManager.recordLocation(recordLocation);
//设置SD卡广播
installIntentFilter();
mImageSaver = new ImageSaver();
//初始化Zoom
initializeZoom();
//mMediaProviderClient=媒体Provider对象
keepMediaProviderInstance();
//检查硬盘
checkStorage();
//淡出retake和done的Button
hidePostCaptureAlert();
if (!mIsImageCaptureIntent) {
//如果不是第三方开启，则更新缩略图
updateThumbnailButton();
mModePicker.setCurrentMode(ModePicker.MODE_CAMERA);
}
}
4、surfaceDestroyed
stopPreview();
mSurfaceHolder = null;