CameraX

1. 调用ProcessCameraProvider.getInstance(),获取可监听的Future对象；
   final ListenableFuture<ProcessCameraProvider> cameraProviderFuture = ProcessCameraProvider.getInstance(this);

2. 为可监听Future对象设置监听器和执行监听器的线程池。在监听器中获取ProcessCameraProvider对象；

    cameraProviderFuture.addListener(new Runnable() {
        @Override
        public void run() {
            try {
   
                ProcessCameraProvider cameraProvider = cameraProviderFuture.get();
                bindPreview(cameraProvider);//进入后续步骤
   
            } catch (ExecutionException | InterruptedException | CameraInfoUnavailableException e) {
                // No errors need to be handled for this Future.
                // This should never be reached.
            }
        }
    }, ContextCompat.getMainExecutor(this));
   

3. 创建CameraSelector对象；
   CameraSelector cameraSelector = new CameraSelector.Builder() .requireLensFacing(CameraSelector.LENS_FACING_BACK) .build();

4. 创建Preview对象；
   Preview preview = new Preview.Builder().build();

5. 创建ImageAnalysis对象；
   ImageAnalysis imageAnalysis = new ImageAnalysis.Builder().build();

6. 创建ImageCapture对象；
   ImageCapture.Builder builder = new ImageCapture.Builder();
final ImageCapture imageCapture = builder .setTargetRotation(this.getWindowManager().getDefaultDisplay().getRotation()) .build();

7. 通过ProcessCameraProvider将CameraSelector对象、Preview对象、ImageAnalysis对象、ImageCapture对象和当前活动的生命周期绑定；
   cameraProvider.bindToLifecycle((LifecycleOwner)this, cameraSelector, preview, imageAnalysis, imageCapture);

8. 为Preview传入SurfaceProvider对象；
   preview.setSurfaceProvider(mPreviewView.createSurfaceProvider());

9. ImageCapture对象调用.takePhoto方法，方法中指定OutPutOptions对象、线程池，和回调对象。
   ImageCapture.OutputFileOptions outputFileOptions = new ImageCapture.OutputFileOptions.Builder(file).build();
   imageCapture.takePicture(outputFileOptions, executor, new ImageCapture.OnImageSavedCallback () {
   @Override
   public void onImageSaved(@NonNull ImageCapture.OutputFileResults outputFileResults) {
   new Handler(Looper.getMainLooper()).post(new Runnable() {
   @Override
   public void run() {
   Toast.makeText(MainActivity.this, "Image Saved successfully", Toast.LENGTH_SHORT).show();
   }
   });
   }
   @Override
   public void onError(@NonNull ImageCaptureException error) {
   error.printStackTrace();
   }
   });

10. 拍照完毕，回调对象的onImageSaved()或onError()调用。