Question

我想要实现的是在不显示预览的情况下捕获图片，直接将输出发送到ImageReader。我使用Camera2Basic example作为起点。但是，我的ImageReader的回调从未被调用，因此没有图像发送到其Surface。我真的需要先显示预览吗？

这是摄像机代码，按照异步回调流程排序：

private ImageReader imageReader;
private Handler backgroundHandler;
private HandlerThread backgroundThread;
private String cameraId;
private CameraDevice cameraDevice;
private CameraCaptureSession cameraCaptureSession;
    @Override
    public void onCreate() {
        setupCamera2();
    }

    private void setupCamera2() {
        CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

        try {

            for (String cameraId : manager.getCameraIdList()) {
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);

            if (characteristics.get(CameraCharacteristics.LENS_FACING) != CameraCharacteristics.LENS_FACING_FRONT) {
                continue;
            }

            this.cameraId = cameraId;

            int[] picSize = Settings.getPictureSize();
            int picWidth = picSize[0];
            int picHeight = picSize[1];

            imageReader = ImageReader.newInstance(picWidth, picHeight, ImageFormat.JPEG, 2);
            imageReader.setOnImageAvailableListener(onImageAvailableListener, backgroundHandler);
            }

        } catch (CameraAccessException | NullPointerException e) {
            e.printStackTrace();
        }
    }


    private void openCamera2() {
        CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        try {

            manager.openCamera(cameraId, cameraStateCallback, backgroundHandler);

        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }



    private final CameraDevice.StateCallback cameraStateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice device) {
            cameraDevice = device;
            createCameraCaptureSession();
        }

        @Override
        public void onDisconnected(CameraDevice cameraDevice) {}

        @Override
        public void onError(CameraDevice cameraDevice, int error) {}
    };



    private void createCaptureSession() {
        List<Surface> outputSurfaces = new LinkedList<>();
        outputSurfaces.add(imageReader.getSurface());

        try {

            cameraDevice.createCaptureSession(outputSurfaces, new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(CameraCaptureSession session) {
                    cameraCaptureSession = session;
                }

                @Override
                public void onConfigureFailed(CameraCaptureSession session) {}
            }, null);

        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }


    private final ImageReader.OnImageAvailableListener onImageAvailableListener = new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            createCaptureRequest();
        }
    };


    private void createCaptureRequest() {
        try {

            CaptureRequest.Builder requestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            requestBuilder.addTarget(imageReader.getSurface());

            // Focus
            requestBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_CONTINUOUS_PICTURE);

            // Orientation
            int rotation = windowManager.getDefaultDisplay().getRotation();
            requestBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));

            cameraCaptureSession.capture(requestBuilder.build(), camera2Callback, null);

        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

Answer 1

您应该在“onConfigured”功能中捕获照片，但不能在onImageAvailable上捕获。

public void onConfigured(CameraCaptureSession session) {
            cameraCaptureSession = session;
            createCaptureRequest();
        }

在此功能“onImageAvailable”中，您应该保存图像，

Image image = mImageReader.acquireLatestImage();
ByteBuffer buffer = image.getPlanes()[0].getBuffer();
byte[] bytes = new byte[buffer.remaining()];
buffer.get(bytes);
try {
    save(bytes, file);
} catch (IOException e) {
    e.printStackTrace();
}
image.close();

在session.capture（）之后将调用

“onImageAvailable”函数。

Answer 2

由于我经常发现它是如何工作的，所以这里有一个可以处理图像数据的最小工作Android服务。创建之前可能需要一些时间，然后才能调用启动服务！

import android.app.Service;
import android.content.Intent;
import android.graphics.ImageFormat;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CaptureRequest;
import android.media.Image;
import android.media.ImageReader;
import android.os.IBinder;
import android.util.Log;

import java.util.Arrays;

public class VideoProcessingService extends Service {
    private static final String TAG = "VideoProcessing";
    private static final int CAMERA = CameraCharacteristics.LENS_FACING_FRONT;
    private CameraDevice camera;
    private CameraCaptureSession session;
    private ImageReader imageReader;

    private CameraDevice.StateCallback cameraStateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(CameraDevice camera) {
            VideoProcessingService.this.camera = camera;
        }

        @Override
        public void onDisconnected(CameraDevice camera) {}

        @Override
        public void onError(CameraDevice camera, int error) {}
    };

    private CameraCaptureSession.StateCallback sessionStateCallback = new CameraCaptureSession.StateCallback() {
        @Override
        public void onConfigured(CameraCaptureSession session) {
            VideoProcessingService.this.session = session;
            try {
                session.setRepeatingRequest(createCaptureRequest(), null, null);
            } catch (CameraAccessException e){
                Log.e(TAG, e.getMessage());
            }
        }

        @Override
        public void onConfigureFailed(CameraCaptureSession session) {}
    };

    private ImageReader.OnImageAvailableListener onImageAvailableListener = new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader){
            Image img = reader.acquireLatestImage();
            processImage(img);
            img.close();
        }
    };

    @Override
    public void onCreate() {
        CameraManager manager = (CameraManager) getSystemService(CAMERA_SERVICE);
        try {
            manager.openCamera(getCamera(manager), cameraStateCallback, null);
            imageReader = ImageReader.newInstance(320, 240, ImageFormat.YUV_420_888, 30 * 600); //fps * 10 min
            imageReader.setOnImageAvailableListener(onImageAvailableListener, null);
        } catch (CameraAccessException e){
            Log.e(TAG, e.getMessage());
        }
    }

    /**
     *  Return the Camera Id which matches the field CAMERA.
     */
    public String getCamera(CameraManager manager){
        try {
            for (String cameraId : manager.getCameraIdList()) {
                CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
                int cOrientation = characteristics.get(CameraCharacteristics.LENS_FACING);
                if (cOrientation == CAMERA) {
                    return cameraId;
                }
            }
        } catch (CameraAccessException e){
            e.printStackTrace();
        }
        return null;
    }

    @Override
    public int onStartCommand(Intent intent, int flags, int startId) {
        try {
            camera.createCaptureSession(Arrays.asList(imageReader.getSurface()), sessionStateCallback, null);
        } catch (CameraAccessException e){
            Log.e(TAG, e.getMessage());
        }
        return super.onStartCommand(intent, flags, startId);
    }

    @Override
    public void onDestroy() {
        try {
            session.abortCaptures();
        } catch (CameraAccessException e){
            Log.e(TAG, e.getMessage());
        }
        session.close();
    }

    /**
     *  Process image data as desired.
     */
    private void processImage(Image image){
        //Process image data
    }

    private CaptureRequest createCaptureRequest() {
        try {
            CaptureRequest.Builder builder = camera.createCaptureRequest(CameraDevice.TEMPLATE_RECORD);
            builder.addTarget(imageReader.getSurface());
            return builder.build();
        } catch (CameraAccessException e) {
            Log.e(TAG, e.getMessage());
            return null;
        }
    }

    @Override
    public IBinder onBind(Intent intent) {
        return null;
    }
}

Answer 3

由于我长期以来一直在努力使用CAMERA2 API，寻找如何从设备上的所有可用相机拍摄无预览的照片，我已经在GitHub上创建了一个完全符合你想要的项目（也许更多） https://github.com/hzitoun/android-camera2-secret-picture-taker

希望有所帮助:)

Answer 4

嘿，在TextureView中对相机进行基本预览时遇到了问题。我找到了拍摄照片，将图片保存到外部目录并且不破坏预览的最佳解决方案！ Camera2 API出现故障。享受<3。还要求事先获得许可！

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="theandroidguy.bart.keepreceipt">

    <uses-permission android:name="android.permission.CAMERA" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/Theme.AppCompat.Light.NoActionBar">
        <activity android:name=".Insert_Receipt_Info_Activity"></activity>
        <activity android:name=".ScanReceipt" />
        <activity
            android:name=".NavigationActivity"
            android:label="KeepReceipt"
            android:theme="@style/Theme.AppCompat.Light.NoActionBar" />
        <activity android:name=".LoginActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".MainActivity" />
    </application>

</manifest>

ScanReceipt.java

package theandroidguy.bart.keepreceipt;

import android.Manifest;
import android.app.AlertDialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.pm.PackageManager;
import android.graphics.ImageFormat;
import android.graphics.SurfaceTexture;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraCharacteristics;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CameraMetadata;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.TotalCaptureResult;
import android.hardware.camera2.params.StreamConfigurationMap;
import android.media.Image;
import android.media.ImageReader;
import android.os.Environment;
import android.os.Handler;
import android.os.HandlerThread;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.util.Size;
import android.util.SparseIntArray;
import android.view.Surface;
import android.view.TextureView;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.UUID;

public class ScanReceipt extends AppCompatActivity{

    private Button btnCapture;
    private TextureView textureView;

    public static final int STORAGE_PERMISSION_REQUEST_CODE= 1;

    //Check state orientation of output image
    private static final SparseIntArray ORIENTATIONS = new SparseIntArray();
    static{
        ORIENTATIONS.append(Surface.ROTATION_0,90);
        ORIENTATIONS.append(Surface.ROTATION_90,0);
        ORIENTATIONS.append(Surface.ROTATION_180,270);
        ORIENTATIONS.append(Surface.ROTATION_270,180);
    }

    private String cameraId;
    private CameraDevice cameraDevice;
    private CameraCaptureSession cameraCaptureSessions;
    private CaptureRequest.Builder captureRequestBuilder;
    private Size imageDimension;
    private ImageReader imageReader;

    //Save to FILE
    private File file;
    private static final int REQUEST_CAMERA_PERMISSION = 200;
    private boolean mFlashSupported;
    private Handler mBackgroundHandler;
    private HandlerThread mBackgroundThread;

    CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
        @Override
        public void onOpened(@NonNull CameraDevice camera) {
            cameraDevice = camera;
            createCameraPreview();
        }

        @Override
        public void onDisconnected(@NonNull CameraDevice cameraDevice) {
            cameraDevice.close();
        }

        @Override
        public void onError(@NonNull CameraDevice cameraDevice, int i) {
            cameraDevice.close();
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_scan_receipt);
        askPermissions();

        textureView = findViewById(R.id.textureView);
        //From Java 1.4 , you can use keyword 'assert' to check expression true or false
        assert textureView != null;
        textureView.setSurfaceTextureListener(textureListener);
        btnCapture = findViewById(R.id.snapPictureBtn);
        btnCapture.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                takePicture();
            }
        });
    }

    protected void takePicture() {
        if(null == cameraDevice) {
            Log.e("No cam", "cameraDevice is null and not being detected!!!");
            return;
        }

        CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
        try {
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraDevice.getId());
            Size[] jpegSizes = null;
            if (characteristics != null) {
                jpegSizes = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP).getOutputSizes(ImageFormat.JPEG);
            }
            int width = 640;
            int height = 480;
            if (jpegSizes != null &&
                        0 < jpegSizes.length) {
                width = jpegSizes[0].getWidth();
                height = jpegSizes[0].getHeight();
            }
            final ImageReader reader = ImageReader.newInstance(width, height, ImageFormat.JPEG, 1);
            List<Surface> outputSurfaces = new ArrayList<Surface>(2);
            outputSurfaces.add(reader.getSurface());
            //i believe this fucks over the preview after snapping
            //outputSurfaces.add(new Surface(textureView.getSurfaceTexture()));
            final CaptureRequest.Builder captureBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            captureBuilder.addTarget(reader.getSurface());
            captureBuilder.set(CaptureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);
            // Orientation
            int rotation = getWindowManager().getDefaultDisplay().getRotation();
            captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, ORIENTATIONS.get(rotation));
            final File file = new File(Environment.getExternalStorageDirectory()+"/picture.jpg");
            ImageReader.OnImageAvailableListener readerListener = new ImageReader.OnImageAvailableListener() {
                @Override
                public void onImageAvailable(ImageReader reader) {
                    Image image = null;
                    try {
                        image = reader.acquireLatestImage();
                        ByteBuffer buffer = image.getPlanes()[0].getBuffer();
                        byte[] bytes = new byte[buffer.capacity()];
                        buffer.get(bytes);
                        save(bytes);
                    } catch (FileNotFoundException e) {
                        e.printStackTrace();
                    } catch (IOException e) {
                        e.printStackTrace();
                    } finally {
                        if (image != null) {
                            image.close();
                        }
                    }
                }
                private void save(byte[] bytes) throws IOException {
                    OutputStream output = null;
                    try {
                        output = new FileOutputStream(file);
                        output.write(bytes);
                    } finally {
                        if (null != output) {
                            output.close();
                        }
                    }
                }
            };
            reader.setOnImageAvailableListener(readerListener, mBackgroundHandler);
            final CameraCaptureSession.CaptureCallback captureListener = new CameraCaptureSession.CaptureCallback() {
                @Override
                public void onCaptureCompleted(@NonNull CameraCaptureSession session, @NonNull CaptureRequest request, @NonNull TotalCaptureResult result) {
                    super.onCaptureCompleted(session, request, result);
                    Toast.makeText(ScanReceipt.this, "Saved:" + file, Toast.LENGTH_SHORT).show();
                    createCameraPreview();
                }
            };
            cameraDevice.createCaptureSession(outputSurfaces, new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(@NonNull CameraCaptureSession session) {
                    try {
                        session.capture(captureBuilder.build(), captureListener, mBackgroundHandler);
                    } catch (CameraAccessException e) {
                        e.printStackTrace();
                    }
                }
                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession session) {
                    Toast.makeText(getApplicationContext(), "Failed on config!", Toast.LENGTH_SHORT).show();
                }
            }, mBackgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }

    }

    private void createCameraPreview() {
        try{
            SurfaceTexture texture = textureView.getSurfaceTexture();
            assert texture != null;
            texture.setDefaultBufferSize(imageDimension.getWidth(),imageDimension.getHeight());
            Surface surface = new Surface(texture);
            captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            captureRequestBuilder.addTarget(surface);
            cameraDevice.createCaptureSession(Arrays.asList(surface), new CameraCaptureSession.StateCallback() {
                @Override
                public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
                    if(cameraDevice == null)
                        return;
                    cameraCaptureSessions = cameraCaptureSession;
                    updatePreview();
                }

                @Override
                public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
                    Toast.makeText(ScanReceipt.this, "Changed", Toast.LENGTH_SHORT).show();
                }
            },null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    private void updatePreview() {
        if(cameraDevice == null)
            Toast.makeText(this, "Error", Toast.LENGTH_SHORT).show();
        captureRequestBuilder.set(CaptureRequest.CONTROL_MODE,CaptureRequest.CONTROL_MODE_AUTO);
        try{
            cameraCaptureSessions.setRepeatingRequest(captureRequestBuilder.build(),null,mBackgroundHandler);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }


    private void openCamera() {
        CameraManager manager = (CameraManager)getSystemService(Context.CAMERA_SERVICE);
        try{
            cameraId = manager.getCameraIdList()[0];
            CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
            StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
            assert map != null;
            imageDimension = map.getOutputSizes(SurfaceTexture.class)[0];
            //Check realtime permission if run higher API 23
            if(ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED)
            {
                ActivityCompat.requestPermissions(this,new String[]{
                        Manifest.permission.CAMERA,
                        Manifest.permission.WRITE_EXTERNAL_STORAGE
                },REQUEST_CAMERA_PERMISSION);
                return;
            }
            manager.openCamera(cameraId,stateCallback,null);

        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    TextureView.SurfaceTextureListener textureListener = new TextureView.SurfaceTextureListener() {
        @Override
        public void onSurfaceTextureAvailable(SurfaceTexture surfaceTexture, int i, int i1) {
            openCamera();
        }

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

        }

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

        @Override
        public void onSurfaceTextureUpdated(SurfaceTexture surfaceTexture) {

        }
    };

    @Override
    protected void onResume() {
        super.onResume();
        startBackgroundThread();
        if(textureView.isAvailable())
            openCamera();
        else
            textureView.setSurfaceTextureListener(textureListener);
    }

    @Override
    protected void onPause() {
        stopBackgroundThread();
        super.onPause();
    }

    private void stopBackgroundThread() {
        mBackgroundThread.quitSafely();
        try{
            mBackgroundThread.join();
            mBackgroundThread= null;
            mBackgroundHandler = null;
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    private void startBackgroundThread() {
        mBackgroundThread = new HandlerThread("Camera Background");
        mBackgroundThread.start();
        mBackgroundHandler = new Handler(mBackgroundThread.getLooper());
    }

    private void askPermissions() {

        int permissionCheckStorage = ContextCompat.checkSelfPermission(this,
                Manifest.permission.WRITE_EXTERNAL_STORAGE);

        // we already asked for permisson & Permission granted, call camera intent
        if (permissionCheckStorage == PackageManager.PERMISSION_GRANTED) {

            //do what you want

        } else {

            // if storage request is denied
            if (ActivityCompat.shouldShowRequestPermissionRationale(this,
                    Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
                AlertDialog.Builder builder = new AlertDialog.Builder(this);
                builder.setMessage("You need to give permission to access storage in order to work this feature.");
                builder.setNegativeButton("CANCEL", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        dialogInterface.dismiss();
                        finish();
                    }
                });
                builder.setPositiveButton("GIVE PERMISSION", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        dialogInterface.dismiss();

                        // Show permission request popup
                        ActivityCompat.requestPermissions(ScanReceipt.this,
                                new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                                STORAGE_PERMISSION_REQUEST_CODE);
                    }
                });
                builder.show();

            } //asking permission for first time
            else {
                // Show permission request popup for the first time
                ActivityCompat.requestPermissions(ScanReceipt.this,
                        new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE},
                        STORAGE_PERMISSION_REQUEST_CODE);

            }

        }
    }
}

Activity_Scan_Receipt.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/Relvativelayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".ScanReceipt">

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentTop="true"
            android:layout_alignParentEnd="true"
            android:layout_alignParentRight="true"
            android:layout_marginStart="8dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="8dp"
            android:gravity="center"
            android:text="Add new receipt"
            android:textAlignment="center"
            android:textSize="16sp"
            app:layout_constraintBottom_toTopOf="@+id/snapPictureBtn"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/receiptscan" />

        <TextView
            android:id="@+id/progressStatusText"
            android:layout_width="300dp"
            android:layout_height="wrap_content"
            android:layout_below="@+id/receiptscan"
            android:layout_marginTop="8dp"
            android:padding="16dp"
            android:paddingLeft="16dp"
            android:paddingRight="16dp"
            android:text="Scan Receipt"
            android:textAlignment="center"
            android:textSize="18sp"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <Button
            android:id="@+id/snapPictureBtn"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_below="@+id/progressStatusText"
            android:layout_marginStart="8dp"
            android:layout_marginEnd="8dp"
            android:layout_marginBottom="16dp"
            android:text="Snap"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.498"
            app:layout_constraintStart_toStartOf="parent" />

        <android.support.v7.widget.CardView
            android:id="@+id/receiptscan"
            android:layout_width="0dp"
            android:layout_height="0dp"
            android:layout_below="@+id/textView"
            android:layout_marginStart="24dp"
            android:layout_marginTop="8dp"
            android:layout_marginEnd="24dp"
            android:layout_marginBottom="8dp"
            android:padding="16dp"
            app:cardCornerRadius="18dp"
            app:layout_constraintBottom_toTopOf="@+id/textView"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toBottomOf="@+id/progressStatusText">

                <TextureView
                    android:id="@+id/textureView"
                    android:layout_width="wrap_content"
                    android:layout_height="wrap_content"
                    android:layout_below="@+id/textView"
                    android:gravity="center"
                    app:layout_constraintTop_toBottomOf="@+id/textView" />

        </android.support.v7.widget.CardView>


</android.support.constraint.ConstraintLayout>

使用camera2 API无需预览即可捕获图片

4 个答案: