camera2 是21之後的api用於代替Camera，提供更加牛X的對相機hardware操作的api

此篇筆記主要是記錄開啟預覽介面
後面會記錄Camera開啟相機預覽的程式碼，對比一下

介面佈局

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
 
>

    <com.arvin.camera3.view.AutoFitTextureView
        android:id="@+id/surface"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content" />

    <Button
        android:id="@+id/capturebtn"
        android:layout_width="wrap_content"
        android:layout_height
 
="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_centerHorizontal="true"
        android:text="拍照" />

    <ImageView
        android:id="@+id/preview"
        android:layout_width="120dp"
        android:layout_height="120dp"
        android:layout_alignParentBottom
 
="true" />

</RelativeLayout>

AutoFitTextureView 繼承自 TextureVeiw

1.首先要初始化view，就是一些findviewbyid

2.示例程式碼是在onResume中，能否有更好方式？？？？

if (surfaceView.isAvailable()) {
    // FIXME: 2016/6/13
    try {
        openCamera(surfaceView.getWidth(), surfaceView.getHeight());
    } catch (Exception e) {
        e.printStackTrace();
    }
} else {
    surfaceView.setSurfaceTextureListener(mSurfaceTextureListener);
}

surfaceView即TextureView

判斷TextureView狀態
可用，開啟相機，否則設定相應的回撥

先看開啟相機的程式碼

private void openCamera(int width, int height) throws Exception {
    Activity activity = getActivity();
    CameraManager manager = (CameraManager) activity.getSystemService(Context.CAMERA_SERVICE);
    if (mCameraOpenCloseLock.tryAcquire(2500, TimeUnit.MILLISECONDS)) {
        manager.openCamera(mCameraId,deviceStateCallback,mPreviewHandler );
    }
}

首先呼叫getSystemService(Context.CAMERA_SERVICE),拿到CameraManager例項，
注：Api 21 新增的，無相容包，估計也不會發布相容包吧，21之後 Camera已棄用
然後通過CameraManager例項的 openCamera()方法開啟相機預覽
我們看下openCamera的宣告

@RequiresPermission(android.Manifest.permission.CAMERA)
public void openCamera(@NonNull String cameraId,
        @NonNull final CameraDevice.StateCallback callback, @Nullable Handler handler)
        throws CameraAccessException {

    if (cameraId == null) {
        throw new IllegalArgumentException("cameraId was null");
    } else if (callback == null) {
        throw new IllegalArgumentException("callback was null");
    } else if (handler == null) {
        if (Looper.myLooper() != null) {
            handler = new Handler();
        } else {
            throw new IllegalArgumentException(
                    "Handler argument is null, but no looper exists in the calling thread");
        }
    }

    openCameraDeviceUserAsync(cameraId, callback, handler);
}

@RequiresPermission(android.Manifest.permission.CAMERA)

需要camera許可權，在camera宣告，android 6.0之後需要請求，屬於runtime permission

需要傳入三個引數
cameraId ： “0”表示後置攝像頭，“1”表示前置攝像頭
callback : CameraDevice.StateCallback 相機狀態回撥
注：CameraDevice 例項代表一個相機
handler : hanlder

回頭看如果TextureView不可用的狀態下

surfaceView.setSurfaceTextureListener(mSurfaceTextureListener);

看下 mSurfaceTextureListener是個什麼東西

private final TextureView.SurfaceTextureListener mSurfaceTextureListener = new TextureView.SurfaceTextureListener() {
    @Override
    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
        try {
            openCamera(width, height);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {

    }

    @Override
    public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
        return false;
    }

    @Override
    public void onSurfaceTextureUpdated(SurfaceTexture surface) {

    }
};

這個有點和SurfaceView的回撥相似了
設定回撥，然後當surface可用的時候openCamera(),回到上面的流程去了
包含四個方法，分別對應可用，尺寸發生變化，TextureView銷燬，以及更新的時候回撥

繼續看manager.openCamera();
已經說了第一個引數camreaId，“0”代表後置攝像頭，“1”代表前置攝像頭
第二個引數CameraDevice.StateCallback， 直接看

CameraDevice.StateCallback deviceStateCallback = new CameraDevice.StateCallback() {
    @Override
    public void onOpened(CameraDevice camera) {
        mCameraOpenCloseLock.release();
        mCameraDevice = camera;
        try {
            createCameraPreviewSession();
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onDisconnected(CameraDevice camera) {
        mCameraOpenCloseLock.release();
        camera.close();
        mCameraDevice = null;
    }

    @Override
    public void onError(CameraDevice camera, int error) {
        mCameraOpenCloseLock.release();
        camera.close();
        mCameraDevice = null;
        Toast.makeText(getActivity(), "onError,error--->" + error, Toast.LENGTH_SHORT).show();
    }
};

通過程式碼可知，CameraDevice.StateCallback 提供了三個回撥方法，分別對應於camrea開啟，失去連線，開啟錯誤的時候回撥，
在開啟的時候會呼叫createCameraPreviewSession() ，看一下方法定義

private void createCameraPreviewSession() throws CameraAccessException {
    initSurface();
    mPreviewBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
    mPreviewBuilder.addTarget(mSurface);

    mCameraDevice.createCaptureSession(Arrays.asList(mSurface), mCaptureSessionStateCallback, mPreviewHandler);
}

private void initSurface() {
    SurfaceTexture sufaceTexture = surfaceView.getSurfaceTexture();
    assert sufaceTexture != null;
    sufaceTexture.setDefaultBufferSize(surfaceView.getWidth(), surfaceView.getHeight());
    mSurface = new Surface(sufaceTexture);
}

首先通過TextureView的getSurfaceTexture() 拿到 對應 SurfaceTexture 是不是SurfaceView的getSurfaceHolder()很像
設定顯示大小，建立Surface例項
之後，呼叫 CameraDevice createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW) 建立預覽請求
並設定target, CaptureRequest.Builder addTarget(Surface surface)
然後呼叫CameraDevice createCaptureSession()，建立一個相機回話

createCaptureSession()需要傳入三個引數
看下宣告

public abstract void createCaptureSession(@NonNull List<Surface> outputs,
        @NonNull CameraCaptureSession.StateCallback callback, @Nullable Handler handler)

List outputs 我的理解是預覽的輸出載體列表，在上面的程式碼中，我們傳入了new Surface(TextureView.getSurface()) 物件
ImageReader 也有 getSurface()方法，ImageReader也可以作為輸出載體

第二個引數CameraCaptureSession.StateCallback 攝像頭採集狀態回撥
直接看程式碼

private CameraCaptureSession.StateCallback mCaptureSessionStateCallback = new CameraCaptureSession.StateCallback() {
    @Override
    public void onConfigured(CameraCaptureSession session) {
        if (null == mCameraDevice) {
            return;
        }
        mSession = session;
        mPreviewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
        mPreviewBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);
        try {
            session.setRepeatingRequest(mPreviewBuilder.build(), mSessionCaptureCallback, mPreviewHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void onConfigureFailed(CameraCaptureSession session) {

    }

};

設定拍攝模式，這裡設定了連拍，flash，其他的模式嘛，我也不清楚了

mPreviewBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);
mPreviewBuilder.set(CaptureRequest.CONTROL_AE_MODE, CaptureRequest.CONTROL_AE_MODE_ON_AUTO_FLASH);


session.setRepeatingRequest(mPreviewBuilder.build(), mSessionCaptureCallback, mPreviewHandler);

設定重複請求，字面上這麼理解

同樣是三個引數
第一個是CaptureRequest.Builder buildI() 這個是前面採集請求builder 通過CameraDevice createCaptureRequest建立的
第二個是攝像頭採集回話採集狀態的回撥

private CameraCaptureSession.CaptureCallback mSessionCaptureCallback = new CameraCaptureSession.CaptureCallback() {
    @Override
    public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
        super.onCaptureCompleted(session, request, result);
    }

    @Override
    public void onCaptureProgressed(CameraCaptureSession session, CaptureRequest request, CaptureResult partialResult) {
        super.onCaptureProgressed(session, request, partialResult);
    }
};

包含兩個狀態，採集進行，採集完成
可以在這裡面去做處理，
貼上一段程式碼

private CameraCaptureSession.CaptureCallback mSessionCaptureCallback = new CameraCaptureSession.CaptureCallback() {

        @Override
        public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
            mSession = session;
            if (!PreferenceHelper.getCameraFormat(getActivity()).equals("DNG")) {
                checkState(result);
            }

        }

        @Override
        public void onCaptureProgressed(CameraCaptureSession session, CaptureRequest request, CaptureResult partialResult) {
            mSession = session;
            if (!PreferenceHelper.getCameraFormat(getActivity()).equals("DNG")) {
                checkState(partialResult);
            }
        }

        private void checkState(CaptureResult result) {
//            mFrameBitmap = mPreviewView.getBitmap();
//            mMainHandler.sendEmptyMessage(1);
            switch (mState) {
                case STATE_PREVIEW:
                    // NOTHING
                    break;
                case STATE_WAITING_CAPTURE:
                    int afState = result.get(CaptureResult.CONTROL_AF_STATE);
                    Log.i("checkState", "afState--->" + afState);
                    if (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) {
                        Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                        Log.i("checkState", "進來了一層,aeState--->" + aeState);
                        if (aeState == null || aeState == CaptureResult.CONTROL_AE_STATE_CONVERGED) {
                            Log.i("checkState", "進來了第二層");
                            mState = STATE_TRY_DO_CAPTURE;
                            doStillCapture();
                        } else {
                            mState = STATE_TRY_CAPTURE_AGAIN;
                            tryCaptureAgain();
                        }
                    }
                    break;
                case STATE_TRY_CAPTURE_AGAIN:
                    Integer aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                    if (aeState == null ||
                            aeState == CaptureResult.CONTROL_AE_STATE_PRECAPTURE ||
                            aeState == CaptureRequest.CONTROL_AE_STATE_FLASH_REQUIRED) {
                        mState = STATE_TRY_DO_CAPTURE;
                    }
                    break;
                case STATE_TRY_DO_CAPTURE:
                    aeState = result.get(CaptureResult.CONTROL_AE_STATE);
                    if (aeState == null || aeState != CaptureResult.CONTROL_AE_STATE_PRECAPTURE) {
                        mState = STATE_TRY_DO_CAPTURE;
                        doStillCapture();
                    }
                    break;
            }
        }
};

至此,開啟相機預覽的程式碼就結束了，後續比如拍照，錄影什麼的以後再分析啦，這裡的api還沒在學習中

最後附上Camera開啟預覽的程式碼，感覺要簡單好多呀

//佈局檔案
<SurfaceView
    android:id="@+id/surface"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

Camera camera;
surfaceView = (SurfaceView) findViewById(R.id.surface);
holder = surfaceView.getHolder();
holder.addCallback(this);  //設定回撥

@Override
public void surfaceCreated(SurfaceHolder holder) {
    camera = Camera.open();
    try {
        camera.setPreviewDisplay(holder);
    } catch (IOException e) {
        e.printStackTrace();
    }
    camera.startPreview();
}

//將camera預覽介面繫結到SurfaceView
//startPreview()

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {

}

程式碼是不是比camera2簡單多了，不過這個預覽介面挺難看的，其他設定也沒有仔細研究，用到的時候再說吧