Android -- Camera源碼簡析，啟動流程

com.android.camera.Camera.java，主要的實現Activity，繼承於ActivityBase。   ActivityBase                                                                             在ActivityBase中執行流程：   onCreate中進行判斷是否是平板； onResume中判斷是否鎖屏，鎖屏&camera不存在時候，mOnResumePending置為true，否則置為false並執行doOnResume； onWindowFocusChanged中判斷是否獲取到焦點&mOnResumePending，滿足的話執行doOnResume； onPause中將mOnResumePending置為false； Camera.java                                                                             接下來分析Camera.java，執行流程：   1、onCreate   復制代碼 // 獲得攝像頭的數量，前置和後置 getPreferredCameraId(); // 獲得對焦設置eg：連續對焦或者其它 String[] defaultFocusModes = getResources().getStringArray(R.array.pref_camera_focusmode_default_array); //實例化Focus管理對象 mFocusManager = new FocusManager(mPreferences, defaultFocusModes); // 開啟線程來啟動攝像頭 mCameraOpenThread.start(); // 是否是第三方應用啟動拍照功能 mIsImageCaptureIntent = isImageCaptureIntent(); // 設置UI布局文件 setContentView(R.layout.camera); if (mIsImageCaptureIntent) {        // 當第三方其送拍照，需要顯示不同的UI，比如取消鍵盤        mReviewDoneButton = (Rotatable) findViewById(R.id.btn_done);        mReviewCancelButton = (Rotatable) findViewById(R.id.btn_cancel);        findViewById(R.id.btn_cancel).setVisibility(View.VISIBLE); } else {        // 反之顯示縮略圖        mThumbnailView = (RotateImageView) findViewById(R.id.thumbnail);        mThumbnailView.enableFilter(false);        mThumbnailView.setVisibility(View.VISIBLE); } // 一個能旋轉的dialog.比如相機設置的dialog,這個類實現了旋轉的父類 mRotateDialog = new RotateDialogController(this, R.layout.rotate_dialog); // 設置camera的ID，寫道SharedPreference中 mPreferences.setLocalId(this, mCameraId); // 更新preference CameraSettings.upgradeLocalPreferences(mPreferences.getLocal()); // 獲得相機數 mNumberOfCameras = CameraHolder.instance().getNumberOfCameras(); //  貌似是獲得是否是快速拍照 mQuickCapture = getIntent().getBooleanExtra(EXTRA_QUICK_CAPTURE, false); // 為當前的preview重置曝光值 resetExposureCompensation(); // 隱藏系統導航欄等 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 {        // 這個join語句就是為了保證openCamera的線程執行完後，當前的線程才開始運行。主要是為了確保camera設備被打開了         mCameraOpenThread.join();         // 線程執行完後置為空來讓系統回收資源         mCameraOpenThread = null;         if (mOpenCameraFail) {             // 打開camera失敗，顯示“無法連接到相機”             Util.showErrorAndFinish(this, R.string.cannot_connect_camera);             return;         } else if (mCameraDisabled) {             // 由於安全政策限制，相機已被停用             Util.showErrorAndFinish(this, R.string.camera_disabled);             return;         } } catch (InterruptedException ex) {            // ignore } //開啟顯示的子線程 mCameraPreviewThread.start(); if (mIsImageCaptureIntent) {     //如果是第三方開啟的 ，setupCaptureParams 設置拍照的參數        setupCaptureParams(); } else {       //設置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); //攝像頭ID mBackCameraId = CameraHolder.instance().getBackCameraId(); mFrontCameraId = CameraHolder.instance().getFrontCameraId(); // 在startPreview裡面有notify方法 synchronized (mCameraPreviewThread) {       try {           mCameraPreviewThread.wait();        } catch (InterruptedException ex) {             // ignore        } } // 初始化各種控制按鈕 initializeIndicatorControl(); //初始化拍照聲音 mCameraSound = new CameraSound(); try {        //確保顯示        mCameraPreviewThread.join(); } catch (InterruptedException ex) {         // ignore } mCameraPreviewThread = null; 復制代碼 2、surfaceCreated   啥都沒做   3、surfaceChanged   復制代碼 // 確保在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();  } 復制代碼 如果是第一次加載，則執行mHandler.sendEmptyMessage(FIRST_TIME_INIT); 對應處理的是initializeFirstTime();   復制代碼 /**      * 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標志，比如開啟了曝光值啊，什麼的         initOnScreenIndicator();         // 位置服務         mLocationManager.recordLocation(recordLocation);           keepMediaProviderInstance();         // 檢查存儲空間和初始化儲存目錄         checkStorage();         // Initialize last picture button.         mContentResolver = getContentResolver();         if (!mIsImageCaptureIntent) {  // no thumbnail in image capture intent             // 初始化縮略圖             initThumbnailButton();         }         // Initialize shutter button.         // 初始化拍照按鈕並設置監聽事件         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);         // 初始化一個圖片的保存線程         mImageSaver = new ImageSaver();         // 設置屏幕亮度         Util.initializeScreenBrightness(getWindow(), getContentResolver());         // 注冊SD卡相關的廣播，比如拔出存儲卡什麼的         installIntentFilter();         // 初始化縮放UI         initializeZoom();         // 更新屏幕上的閃光燈什麼的標記         updateOnScreenIndicators();         // 開始面部檢測         startFaceDetection();         // Show the tap to focus toast if this is the first start.         // 假如是第一次啟動，提示用戶“觸摸對焦”         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();     } 復制代碼 如果不是，則執行initializeSecondTime();   復制代碼 /**      *  // 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.         //方向翻轉設置enable，其中包括翻轉的時候的動畫         mOrientationListener.enable();           // Start location update if needed.         boolean recordLocation = RecordLocationPreference.get(                 mPreferences, getContentResolver());         mLocationManager.recordLocation(recordLocation);         //設置SD卡廣播         installIntentFilter();         mImageSaver = new ImageSaver();         //初始化Zoom         initializeZoom();         //mMediaProviderClient=媒體Provider對象         keepMediaProviderInstance();         //檢查硬盤         checkStorage();         //淡出retake和done的Button         hidePostCaptureAlert();         if (!mIsImageCaptureIntent) {             //如果不是第三方開啟，則更新縮略圖             updateThumbnailButton();             mModePicker.setCurrentMode(ModePicker.MODE_CAMERA);         }     } 復制代碼 4、surfaceDestroyed   stopPreview(); mSurfaceHolder = null;