Android 用 camera2 API 自定義相機

<TextureView
        android:id="@+id/camera_texture_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

<ImageButton
        android:id="@+id/capture_ib"
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:layout_marginBottom="10dp"
        android:layout_gravity="bottom|center"
        android:background="@drawable/send_pres"/>

</LinearLayout></code></pre>

界面很簡單，只有一個 TexureView 和一個按鈕。

接下來在 Activity 中初始化并顯示相機捕捉的畫面。

首先要解決的一個問題就是畫面拉伸的問題。

要解決這個問題，首先要從 TextureView 下手。

CameraActivity.java

mTextureView.setSurfaceTextureListener(new TextureView.SurfaceTextureListener() {
            @Override
            public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int width, int height) {
                mWidth = width;
                mHeight = height;
                getCameraId();
                openCamera();
            }


        @Override
        public void onSurfaceTextureSizeChanged(SurfaceTexture surfaceTexture, int i, int i1) {

        }

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

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) {

        }
    });</code></pre> 

在 onSurfaceTextureAvailable 中初始化相機。通過 CameraManager 對象 openCamera，這正是流程圖中 Init 步驟中的第一步。openCamera 有三個參數，第一個是 String 類型的 cameraId，第二個是 CameraDevice.StateCallback，第三個是 Handler。這里我們要聲明一個 StateCallback：
 
  
private CameraDevice.StateCallback mCameraDeviceStateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice cameraDevice) {
            mCameraDevice = cameraDevice;
            createCameraPreview();
        }

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

        @Override
        public void onError(CameraDevice cameraDevice, int i) {
            mCameraDevice.close();
            mCameraDevice = null;
        }
    };
 
  
可以看到，在 camera 準備完畢之后就可以創建預覽界面了。解決畫面拉伸的問題就是要為預覽界面設置一個合適比例的 SurfaceTexture buffer size。
 
  
private void createCameraPreview() {
        try {
            SurfaceTexture texture = mTextureView.getSurfaceTexture();
            assert texture != null;
            CameraCharacteristics characteristics = mCameraManager.getCameraCharacteristics(mCameraId);
            StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            int deviceOrientation = getWindowManager().getDefaultDisplay().getOrientation();
            int totalRotation = sensorToDeviceRotation(characteristics, deviceOrientation);
            boolean swapRotation = totalRotation == 90 || totalRotation == 270;
            int rotatedWidth = mWidth;
            int rotatedHeight = mHeight;
            if (swapRotation) {
                rotatedWidth = mHeight;
                rotatedHeight = mWidth;
            }
            mPreviewSize = getPreferredPreviewSize(map.getOutputSizes(SurfaceTexture.class), rotatedWidth, rotatedHeight);
            texture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
            Log.e("CameraActivity", "OptimalSize width: " + mPreviewSize.getWidth() + " height: " + mPreviewSize.getHeight());
            ...
 
  
這里根據當前設備及傳感器的旋轉角度來判斷是否交換寬高值，然后通過 CameraCharacteristics 來得到最適合當前大小比例的寬高，然后把這個寬高設置給 SurfaceTexture 。
 
  
private Size getPreferredPreviewSize(Size[] sizes, int width, int height) {
        List<Size> collectorSizes = new ArrayList<>();
        for (Size option : sizes) {
            if (width > height) {
                if (option.getWidth() > width && option.getHeight() > height) {
                    collectorSizes.add(option);
                }
            } else {
                if (option.getHeight() > width && option.getWidth() > height) {
                    collectorSizes.add(option);
                }
            }
        }
        if (collectorSizes.size() > 0) {
            return Collections.min(collectorSizes, new Comparator<Size>() {
                @Override
                public int compare(Size s1, Size s2) {
                    return Long.signum(s1.getWidth() * s1.getHeight() - s2.getWidth() * s2.getHeight());
                }
            });
        }
        return sizes[0];
    }
 
  
這里 Sizes 是相機返回的支持的分辨率，從我們傳遞的參數找找到一個最接近的分辨率。
 
  
接下來就要通過 CaptureRequest.Builder以及 CameraCaptureSession.StateCallback 來創建及更新預覽界面：
 
  
...
Surface surface = new Surface(texture);
            mBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            // 設置預覽對象
            mBuilder.addTarget(surface);
            mCameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(CameraCaptureSession cameraCaptureSession) {
                    if (null == mCameraDevice) {
                        return;
                    }
                    mSession = cameraCaptureSession;
                    mBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
                    try {
                        // 不停地將捕捉的畫面更新到 TextureView
                        mSession.setRepeatingRequest(mBuilder.build(), mSessionCaptureCallback, mBackgroundHandler);
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                }

                @Override
                public void onConfigureFailed(CameraCaptureSession cameraCaptureSession) {
                    Toast.makeText(CameraActivity.this, "Camera configuration change", Toast.LENGTH_SHORT).show();
                }
            }, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
 
  
 
 
  
來自：http://www.cnblogs.com/jpush88/p/6670724.html