Android开发又一新挑战！CameraX 即将一统江湖？

你可能没想到 CameraX也是 Jetpack 的一部分。



前言



Camera2






CameraX

图像预览

private void setupCamera(PreviewView previewView) {    ListenableFuture<ProcessCameraProvider> cameraProviderFuture =            ProcessCameraProvider.getInstance(this);    cameraProviderFuture.addListener(() -> {        try {            mCameraProvider = cameraProviderFuture.get();            bindPreview(mCameraProvider, previewView);        } catch (ExecutionException | InterruptedException e) {            e.printStackTrace();        }    }, ContextCompat.getMainExecutor(this));}private void bindPreview(@NonNull ProcessCameraProvider cameraProvider,                         PreviewView previewView) {    mPreview = new Preview.Builder().build();    mCamera = cameraProvider.bindToLifecycle(this,            CameraSelector.DEFAULT_BACK_CAMERA, mPreview);    mPreview.setSurfaceProvider(previewView.getSurfaceProvider());}


镜头切换

public void onChangeGo(View view) {    if (mCameraProvider != null) {        isBack = !isBack;        bindPreview(mCameraProvider, binding.previewView);    }}private void bindPreview(@NonNull ProcessCameraProvider cameraProvider,                         PreviewView previewView) {    ...    CameraSelector cameraSelector = isBack ? CameraSelector.DEFAULT_BACK_CAMERA            : CameraSelector.DEFAULT_FRONT_CAMERA;    // 绑定前确保解除了所有绑定，防止CameraProvider重复绑定到Lifecycle发生异常    cameraProvider.unbindAll();     mCamera = cameraProvider.bindToLifecycle(this, cameraSelector, mPreview);    ...}


镜头聚焦

protected void onCreate(@Nullable Bundle savedInstanceState) {    ...    binding.previewView.setOnTouchListener((v, event) -> {        FocusMeteringAction action = new FocusMeteringAction.Builder(                binding.previewView.getMeteringPointFactory()                        .createPoint(event.getX(), event.getY())).build();        try {            showTapView((int) event.getX(), (int) event.getY());            mCamera.getCameraControl().startFocusAndMetering(action);        }...    });}private void showTapView(int x, int y) {    PopupWindow popupWindow = new PopupWindow(ViewGroup.LayoutParams.WRAP_CONTENT,            ViewGroup.LayoutParams.WRAP_CONTENT);    ImageView imageView = new ImageView(this);    imageView.setImageResource(R.drawable.ic_focus_view);    popupWindow.setContentView(imageView);    popupWindow.showAsDropDown(binding.previewView, x, y);    binding.previewView.postDelayed(popupWindow::dismiss, 600);    binding.previewView.playSoundEffect(SoundEffectConstants.CLICK);}




图像拍摄

private void takenPictureInternal(boolean isExternal) {    final ContentValues contentValues = new ContentValues();    contentValues.put(MediaStore.MediaColumns.DISPLAY_NAME, CAPTURED_FILE_NAME            + "_" + picCount++);    contentValues.put(MediaStore.MediaColumns.MIME_TYPE, "image/jpeg");    ImageCapture.OutputFileOptions outputFileOptions =             new ImageCapture.OutputFileOptions.Builder(                    getContentResolver(),                    MediaStore.Images.Media.EXTERNAL_CONTENT_URI, contentValues)            .build();    if (mImageCapture != null) {        mImageCapture.takePicture(outputFileOptions, CameraXExecutors.mainThreadExecutor(),                new ImageCapture.OnImageSavedCallback() {                    @Override                    public void onImageSaved(@NonNull ImageCapture.OutputFileResults outputFileResults) {                        Toast.makeText(DemoActivityLite.this, "Picture got"                                + (outputFileResults.getSavedUri() != null                                ? " @ " + outputFileResults.getSavedUri().getPath()                                : "") + ".", Toast.LENGTH_SHORT)                                .show();                    }                    ...                });    }}private void bindPreview(@NonNull ProcessCameraProvider cameraProvider,                         PreviewView previewView) {    ...    mImageCapture =  new ImageCapture.Builder()            .setTargetRotation(previewView.getDisplay().getRotation())            .build();    ...    // 需要将ImageCapture场景一并绑定    mCamera = cameraProvider.bindToLifecycle(this, cameraSelector, mPreview, mImageCapture);    ...}


图像分析


public void onAnalyzeGo(View view) {    if (!isAnalyzing) {        mImageAnalysis.setAnalyzer(CameraXExecutors.mainThreadExecutor(), image -> {           analyzeQRCode(image);        });    }    ...}// 从ImageProxy取出图像数据，交由二维码框架zxing解析private void analyzeQRCode(@NonNull ImageProxy imageProxy) {    ByteBuffer byteBuffer = imageProxy.getPlanes()[0].getBuffer();    byte[] data = new byte[byteBuffer.remaining()];    byteBuffer.get(data);    ...    BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));    Result result;    try {        result = multiFormatReader.decode(bitmap);    }    ...    showQRCodeResult(result);    imageProxy.close();}private void showQRCodeResult(@Nullable Result result) {    if (binding != null && binding.qrCodeResult != null) {        binding.qrCodeResult.post(() ->                binding.qrCodeResult.setText(result != null ? "Link:\n" + result.getText() : ""));        binding.qrCodeResult.playSoundEffect(SoundEffectConstants.CLICK);    }}


视频录制


public void onVideoGo(View view) {    bindPreview(mCameraProvider, binding.previewView, isVideoMode);}private void bindPreview(@NonNull ProcessCameraProvider cameraProvider,                         PreviewView previewView, boolean isVideo) {    ...    mVideoCapture = new VideoCapture.Builder()            .setTargetRotation(previewView.getDisplay().getRotation())            .setVideoFrameRate(25)            .setBitRate(3 * 1024 * 1024)            .build();    cameraProvider.unbindAll();    if (isVideo) {        mCamera = cameraProvider.bindToLifecycle(this, cameraSelector,                mPreview, mVideoCapture);    } else {        mCamera = cameraProvider.bindToLifecycle(this, cameraSelector,                mPreview, mImageCapture, mImageAnalysis);    }    mPreview.setSurfaceProvider(previewView.getSurfaceProvider());}
public void onCaptureGo(View view) {    if (isVideoMode) {        if (!isRecording) {            // Check permission first.            ensureAudioStoragePermission(REQUEST_STORAGE_VIDEO);        }    }    ...}private void ensureAudioStoragePermission(int requestId) {    ...    if (requestId == REQUEST_STORAGE_VIDEO) {        if (ActivityCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)                != PackageManager.PERMISSION_GRANTED                || ActivityCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO)                != PackageManager.PERMISSION_GRANTED) {            ActivityCompat.requestPermissions(...);            return;        }        recordVideo();    }}private void recordVideo() {   try {        mVideoCapture.startRecording(                new VideoCapture.OutputFileOptions.Builder(getContentResolver(),                        MediaStore.Video.Media.EXTERNAL_CONTENT_URI, contentValues)                        .build(),                CameraXExecutors.mainThreadExecutor(),                new VideoCapture.OnVideoSavedCallback() {                    @Override                    public void onVideoSaved(@NonNull VideoCapture.OutputFileResults outputFileResults) {                        // Notify user...                    }                }        );    }     ...    toggleRecordingStatus();}private void toggleRecordingStatus() {    // Stop recording when toggle to false.    if (!isRecording && mVideoCapture != null) {        mVideoCapture.stopRecording();    }}

• 小插曲
  

// VideoCapture.javapublic void startRecording(        @NonNull OutputFileOptions outputFileOptions, @NonNull Executor executor,        @NonNull OnVideoSavedCallback callback) {    ...    try {        // mAudioRecorder为null将引发NPE终止录制的请求        mAudioRecorder.startRecording();    } catch (IllegalStateException e) {        postListener.onError(ERROR_ENCODER, "AudioRecorder start fail", e);        return;    }    ...    mRecordingFuture.addListener(() -> {        ...        if (getCamera() != null) {            // 前面发生了NPE,那么将失去此处再次获得AudioRecorder实例的机会            setupEncoder(getCameraId(), getAttachedSurfaceResolution());            notifyReset();        }    }, CameraXExecutors.mainThreadExecutor());    ...}



相机效果扩展










private void bindPreview(@NonNull ProcessCameraProvider cameraProvider,                         PreviewView previewView, boolean isVideo) {    Preview.Builder previewBuilder = new Preview.Builder();    ImageCapture.Builder captureBuilder = new ImageCapture.Builder()            .setTargetRotation(previewView.getDisplay().getRotation());    ...    setPreviewExtender(previewBuilder, cameraSelector);    mPreview = previewBuilder.build();    setCaptureExtender(captureBuilder, cameraSelector);    mImageCapture =  captureBuilder.build();    ...}private void setPreviewExtender(Preview.Builder builder, CameraSelector cameraSelector) {    BeautyPreviewExtender beautyPreviewExtender = BeautyPreviewExtender.create(builder);    if (beautyPreviewExtender.isExtensionAvailable(cameraSelector)) {        // Enable the extension if available.        beautyPreviewExtender.enableExtension(cameraSelector);    }}private void setCaptureExtender(ImageCapture.Builder builder, CameraSelector cameraSelector) {    NightImageCaptureExtender nightImageCaptureExtender = NightImageCaptureExtender.create(builder);    if (nightImageCaptureExtender.isExtensionAvailable(cameraSelector)) {        // Enable the extension if available.        nightImageCaptureExtender.enableExtension(cameraSelector);    }}
高阶用法





使用注意

• 调用CameraProvider的bindToLifecycle()前记得先调用unbindAll()，否则可能发生重复绑定的exception。
  
• ImageAnalyzer的analyze()在分析完图片之后应立即调用ImageProxy的close()释放图像，以便后续图像能继续传送过来。否则将阻塞回调。因而也要注意分析图像的耗时问题。
  
• 每个ImageProxy实例在关闭后不要存储它的引用，因为一旦调用close()，这些图像将变得不合法。
  
• 图像分析结束后应当调用ImageAnalysis的clearAnalyzer()以告知不用将图像流传输过来避免性能的浪费。
  
• 视频录制场景一定不要忘记获得audio权限。
  

有趣的兼容性处理

Before triggering the image capture pipeline, if the save location is a File or MediaStore, it is first verified to ensure it’s valid and writable.

A File is verified by attempting to open a FileOutputStream to it, whereas a location in MediaStore is validated by ContentResolver#insert() creating a new row in the user defined table,

retrieving a Uri pointing to it, then attempting to open an OutputStream to it.
The newly created row is ContentResolver#delete() deleted at the end of the verification.

On Huawei devices, this deletion results in the system displaying a notification informing the user that a photo has been deleted.

In order to avoid this, validating the image capture save location in MediaStore is skipped on Huawei devices.

class ImageSaveLocationValidator {    // 将判断设备品牌是否为华为或荣耀，是则直接跳过验证    static boolean isValid(final @NonNull ImageCapture.OutputFileOptions outputFileOptions) {        ...        if (isSaveToMediaStore(outputFileOptions)) {            // Skip verification on Huawei devices            final HuaweiMediaStoreLocationValidationQuirk huaweiQuirk =                    DeviceQuirks.get(HuaweiMediaStoreLocationValidationQuirk.class);            if (huaweiQuirk != null) {                return huaweiQuirk.canSaveToMediaStore();            }            return canSaveToMediaStore(outputFileOptions.getContentResolver(),                    outputFileOptions.getSaveCollection(), outputFileOptions.getContentValues());        }        return true;    }    ...}public class HuaweiMediaStoreLocationValidationQuirk implements Quirk {    static boolean load() {        return "HUAWEI".equals(Build.BRAND.toUpperCase())                || "HONOR".equals(Build.BRAND.toUpperCase());    }    /**     * Always skip checking if the image capture save destination in     * {@link android.provider.MediaStore} is valid.     */    public boolean canSaveToMediaStore() {        return true;    }}CameraX的优势

• 易用性 采用封装的API可以高效达到目标。
  
• 设备一致性 不用在乎版本，忽略硬件差异，达到一致的开发体验。
  
• 新的相机体验 通过效果扩展可以实现和原生相机一样的美颜等拍摄功能。
  

结语