Android -- Camera源碼簡析，啟動(dòng)流程

com.android.camera.Camera.java，主要的實(shí)現(xiàn)Activity，繼承于ActivityBase。

ActivityBase

在ActivityBase中執(zhí)行流程：

onCreate中進(jìn)行判斷是否是平板;

onResume中判斷是否鎖屏，鎖屏camera不存在時(shí)候，mOnResumePending置為true，否則置為false并執(zhí)行doOnResume;

onWindowFocusChanged中判斷是否獲取到焦點(diǎn)mOnResumePending，滿足的話執(zhí)行doOnResume;

onPause中將mOnResumePending置為false;

Camera.java

接下來分析Camera.java，執(zhí)行流程：

1、onCreate

復(fù)制代碼

// 獲得攝像頭的數(shù)量，前置和后置

getPreferredCameraId();

// 獲得對焦設(shè)置eg：連續(xù)對焦或者其它

String[] defaultFocusModes = getResources().getStringArray(R.array.pref_camera_focusmode_default_array);

//實(shí)例化Focus管理對象

mFocusManager = new FocusManager(mPreferences, defaultFocusModes);

// 開啟線程來啟動(dòng)攝像頭

mCameraOpenThread.start();

// 是否是第三方應(yīng)用啟動(dòng)拍照功能

mIsImageCaptureIntent = isImageCaptureIntent();

// 設(shè)置UI布局文件

setContentView(R.layout.camera);

if (mIsImageCaptureIntent) {

// 當(dāng)?shù)谌狡渌团恼眨枰@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(gè)能旋轉(zhuǎn)的dialog.比如相機(jī)設(shè)置的dialog,這個(gè)類實(shí)現(xiàn)了旋轉(zhuǎn)的父類

mRotateDialog = new RotateDialogController(this, R.layout.rotate_dialog);

// 設(shè)置camera的ID，寫道SharedPreference中

mPreferences.setLocalId(this, mCameraId);

// 更新preference

CameraSettings.upgradeLocalPreferences(mPreferences.getLocal());

// 獲得相機(jī)數(shù)

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(dāng)前的preview重置曝光值

resetExposureCompensation();

// 隱藏系統(tǒng)導(dǎo)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(gè)join語句就是為了保證openCamera的線程執(zhí)行完后，當(dāng)前的線程才開始運(yùn)行。主要是為了確保camera設(shè)備被打開了

mCameraOpenThread.join();

// 線程執(zhí)行完后置為空來讓系統(tǒng)回收資源

mCameraOpenThread = null;

if (mOpenCameraFail) {

// 打開camera失敗，顯示“無法連接到相機(jī)”

Util.showErrorAndFinish(this, R.string.cannot_connect_camera);

return;

} else if (mCameraDisabled) {

// 由于安全政策限制，相機(jī)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(shè)置拍照的參數(shù)

setupCaptureParams();

} else {

//設(shè)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里面有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(fù)制代碼

2、surfaceCreated

啥都沒做

3、surfaceChanged

復(fù)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