API 21中将原来的camera API弃用转而推荐使用新增的camera2 API，这是一个大的动作，因为新API换了架构，让开发者用起来更难了。 
先来看看camera2包架构示意图： 
 
这里引用了管道的概念将安卓设备和摄像头之间联通起来，系统向摄像头发送Capture请求，而摄像头会返回CameraMetadata。这一切建立在一个叫作CameraCaptureSession的会话中。

下面是camera2包中的主要类： 
 
其中CameraManager是那个站在高处统管所有摄像投设备（CameraDevice）的管理者，而每个CameraDevice自己会负责建立CameraCaptureSession以及建立CaptureRequest。CameraCharacteristics是CameraDevice的属性描述类，非要做个对比的话，那么它与原来的CameraInfo有相似性。 
类图中有着三个重要的callback，虽然这增加了阅读代码的难度，但是你必须要习惯，因为这是新包的风格。其中CameraCaptureSession.CaptureCallback将处理预览和拍照图片的工作，需要重点对待。

这些类是如何相互配合的？下面是简单的流程图。 

我是用SurfaceView作为显示对象（当然还可以TextureView去显示，详见参考中的项目） 
核心代码如下：

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">        mCameraManager = (CameraManager) <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">this</span>.getSystemService(Context.CAMERA_SERVICE);mSurfaceView = (SurfaceView)findViewById(R.id.surfaceview);mSurfaceHolder = mSurfaceView.getHolder();mSurfaceHolder.addCallback(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> SurfaceHolder.Callback() {<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">surfaceCreated</span>(SurfaceHolder holder) {initCameraAndPreview();}});</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    private void initCameraAndPreview() {Log<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.d</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"linc"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"init camera and preview"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>HandlerThread handlerThread = new HandlerThread(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"Camera2"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>handlerThread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.start</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mHandler = new Handler(handlerThread<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getLooper</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>try {mCameraId = <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">""</span>+CameraCharacteristics<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.LENS</span>_FACING_FRONT<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mImageReader = ImageReader<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.newInstance</span>(mSurfaceView<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getWidth</span>(), mSurfaceView<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getHeight</span>(),ImageFormat<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.JPEG</span>,<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">/*maxImages*/</span><span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">7</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mImageReader<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setOnImageAvailableListener</span>(mOnImageAvailableListener, mHandler)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mCameraManager<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.openCamera</span>(mCameraId, DeviceStateCallback, mHandler)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>} catch (CameraAccessException e) {Log<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.e</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"linc"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"open camera failed."</span> + e<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getMessage</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li></ul>

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> CameraDevice.StateCallback DeviceStateCallback = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> CameraDevice.StateCallback() {<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onOpened</span>(CameraDevice camera) {Log.d(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"linc"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"DeviceStateCallback:camera was opend."</span>);mCameraOpenCloseLock.release();mCameraDevice = camera;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {createCameraCaptureSession();} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (CameraAccessException e) {e.printStackTrace();}}};</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li></ul>

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    private void createCameraCaptureSession() throws CameraAccessException {Log<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.d</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"linc"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"createCameraCaptureSession"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mPreviewBuilder = mCameraDevice<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.createCaptureRequest</span>(CameraDevice<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.TEMPLATE</span>_PREVIEW)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mPreviewBuilder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.addTarget</span>(mSurfaceHolder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getSurface</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mState = STATE_PREVIEW<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mCameraDevice<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.createCaptureSession</span>(Arrays<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.asList</span>(mSurfaceHolder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getSurface</span>(), mImageReader<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getSurface</span>()),mSessionPreviewStateCallback, mHandler)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li></ul>

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">private CameraCaptureSession<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.StateCallback</span> mSessionPreviewStateCallback = newCameraCaptureSession<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.StateCallback</span>() {@Overridepublic void onConfigured(CameraCaptureSession session) {Log<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.d</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"linc"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mSessionPreviewStateCallback onConfigured"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mSession = session<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>try {mPreviewBuilder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(CaptureRequest<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.CONTROL</span>_AF_MODE,CaptureRequest<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.CONTROL</span>_AF_MODE_CONTINUOUS_PICTURE)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>mPreviewBuilder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.set</span>(CaptureRequest<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.CONTROL</span>_AE_MODE,CaptureRequest<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.CONTROL</span>_AE_MODE_ON_AUTO_FLASH)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>session<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.setRepeatingRequest</span>(mPreviewBuilder<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.build</span>(), mSessionCaptureCallback, mHandler)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>} catch (CameraAccessException e) {e<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.printStackTrace</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>Log<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.e</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"linc"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"set preview builder failed."</span>+e<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getMessage</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}}}<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li></ul>

<code class="hljs java has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> CameraCaptureSession.CaptureCallback mSessionCaptureCallback =<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> CameraCaptureSession.CaptureCallback() {<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCaptureCompleted</span>(CameraCaptureSession session, CaptureRequest request,TotalCaptureResult result) {
<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//            Log.d("linc","mSessionCaptureCallback, onCaptureCompleted");</span>mSession = session;checkState(result);}<span class="hljs-annotation" style="color: rgb(155, 133, 157); box-sizing: border-box;">@Override</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCaptureProgressed</span>(CameraCaptureSession session, CaptureRequest request,CaptureResult partialResult) {Log.d(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"linc"</span>,<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mSessionCaptureCallback, onCaptureProgressed"</span>);mSession = session;checkState(partialResult);}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">checkState</span>(CaptureResult result) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">switch</span> (mState) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> STATE_PREVIEW:<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// NOTHING</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">case</span> STATE_WAITING_CAPTURE:<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> afState = result.get(CaptureResult.CONTROL_AF_STATE);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span> (CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED == afState ||CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED == afState|| CaptureResult.CONTROL_AF_STATE_PASSIVE_FOCUSED == afState|| CaptureResult.CONTROL_AF_STATE_PASSIVE_UNFOCUSED == afState) {<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//do something like save picture</span>}<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>;}}};</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li><li style="box-sizing: border-box; padding: 0px 5px;">27</li><li style="box-sizing: border-box; padding: 0px 5px;">28</li><li style="box-sizing: border-box; padding: 0px 5px;">29</li><li style="box-sizing: border-box; padding: 0px 5px;">30</li><li style="box-sizing: border-box; padding: 0px 5px;">31</li><li style="box-sizing: border-box; padding: 0px 5px;">32</li><li style="box-sizing: border-box; padding: 0px 5px;">33</li><li style="box-sizing: border-box; padding: 0px 5px;">34</li><li style="box-sizing: border-box; padding: 0px 5px;">35</li><li style="box-sizing: border-box; padding: 0px 5px;">36</li><li style="box-sizing: border-box; padding: 0px 5px;">37</li><li style="box-sizing: border-box; padding: 0px 5px;">38</li></ul>

按下capture按钮：

<code class="hljs cs has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;">    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> <span class="hljs-title" style="box-sizing: border-box;">onCapture</span>(View view) {<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {Log.i(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"linc"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"take picture"</span>);mState = STATE_WAITING_CAPTURE;mSession.setRepeatingRequest(mPreviewBuilder.build(), mSessionCaptureCallback, mHandler);} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">catch</span> (CameraAccessException e) {e.printStackTrace();}}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li></ul>

测试用genemotion模拟器，直接调用笔记本的摄像头。 
配置图如下： 
 
demo界面如下图： 

源码： 
请参考github中的两个demo项目： 
https://github.com/pinguo-yuyidong/Camera2 
https://github.com/googlesamples/android-Camera2Basic