如何使用Android的Camera2 API

Question

[我正在尝试使用camera2 API创建可以拍照的应用程序，并将其保存到我的设备中以备后用。

我目前在拍照方面存在问题，预览效果很好，但是当我尝试拍照时却无法这样做。

package uk.ac.abertay.cmp309_courswork_1700673_keiranwait;

import android.Manifest;
import android.content.Context;
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.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.HandlerThread;
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 androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

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;

public class CameraActivity extends AppCompatActivity {

Button button;
TextureView textureView;
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;
CameraDevice cameraDevice;
CameraCaptureSession cameraCaptureSession;
CaptureRequest captureRequest;
CaptureRequest.Builder captureRequestBuilder;

private Size imageDimensions;
private ImageReader imageReader;
private File file;
Handler mBackgroundHandler;
HandlerThread mBackgroundThread;

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

    textureView = findViewById(R.id.texture);
    button = findViewById(R.id.btnPic);
    textureView.setSurfaceTextureListener(textureListener);


    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            try {
                takePicture();
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }
        }
    });


}

@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    if (requestCode == 101){
        if (grantResults[0] == PackageManager.PERMISSION_DENIED){
            Toast.makeText(getApplicationContext(),"Sorry Camera Permission Denied",Toast.LENGTH_SHORT).show();
            //  finish();
        }
    }
}

TextureView.SurfaceTextureListener textureListener = new TextureView.SurfaceTextureListener() {
    @Override
    public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
        try {
            openCamera();
        } catch (CameraAccessException 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) {

    }
};

private final CameraDevice.StateCallback stateCallback = new CameraDevice.StateCallback() {
    @Override
    public void onOpened(CameraDevice camera) {
        cameraDevice = camera;
        try {
            createCameraPreview();
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }

    }

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

    @Override
    public void onError(CameraDevice camera, int error) {
        cameraDevice.close();
        cameraDevice = null;
    }
};

private void createCameraPreview() throws CameraAccessException {
    SurfaceTexture texture = textureView.getSurfaceTexture();
    texture.setDefaultBufferSize(imageDimensions.getWidth(), imageDimensions.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(CameraCaptureSession session) {
            Toast.makeText(getApplicationContext(),"On Config",Toast.LENGTH_SHORT).show();
            if (cameraDevice == null) {
                return;
            }

            cameraCaptureSession = session;
            try {
                updatePreview();
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }


        }

        @Override
        public void onConfigureFailed(CameraCaptureSession session) {
            Toast.makeText(getApplicationContext(),"Configuration Changed",Toast.LENGTH_SHORT).show();

        }
    },null);


}

private void updatePreview() throws CameraAccessException {
    if (cameraDevice == null) {
        return;
    }

    captureRequestBuilder.set(captureRequest.CONTROL_MODE, CameraMetadata.CONTROL_MODE_AUTO);

    cameraCaptureSession.setRepeatingRequest(captureRequestBuilder.build(),null, mBackgroundHandler);

}

private void openCamera() throws CameraAccessException {
    CameraManager manager = (CameraManager)getSystemService(Context.CAMERA_SERVICE);

    cameraId = manager.getCameraIdList()[0];
    CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraId);
    StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
    imageDimensions = map.getOutputSizes(SurfaceTexture.class) [0];

    if (ActivityCompat.checkSelfPermission(this,Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED &&
    ActivityCompat.checkSelfPermission(this,Manifest.permission.WRITE_EXTERNAL_STORAGE) != PackageManager.PERMISSION_GRANTED)
    {
        ActivityCompat.requestPermissions(CameraActivity.this,new String[]{Manifest.permission.CAMERA,Manifest.permission.WRITE_EXTERNAL_STORAGE},101);
        return;
    }


    manager.openCamera(cameraId,stateCallback,null);


}

private void takePicture() throws CameraAccessException {
    if (cameraDevice == null){
        return;
    }

    CameraManager manager = (CameraManager)getSystemService(Context.CAMERA_SERVICE);

    CameraCharacteristics characteristics = manager.getCameraCharacteristics(cameraDevice.getId());
    Size[] jpegSizes = null;
    jpegSizes = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP).getOutputSizes(ImageFormat.JPEG);

    int width = 640;
    int height = 480;

    if (jpegSizes != null && jpegSizes.length > 0){
        width = jpegSizes[0].getWidth();
        height = jpegSizes[0].getHeight();
    }

    ImageReader reader = ImageReader.newInstance(width,height,ImageFormat.JPEG,1);
    List<Surface> outputSurfaces = new ArrayList<>(2);
    outputSurfaces.add(reader.getSurface());

    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);
    int rotation = getWindowManager().getDefaultDisplay().getRotation();
    captureBuilder.set(captureRequest.JPEG_ORIENTATION,orientations.get(rotation));

    Long tsLong = System.currentTimeMillis() /1000;
    String ts = tsLong.toString();

    file = new File(Environment.getExternalStorageDirectory() + "/" + ts+".jpg");

    ImageReader.OnImageAvailableListener readerListener = new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            Toast.makeText(getApplicationContext(),"Image Avail",Toast.LENGTH_SHORT).show();
            Image image = null;
            image = reader.acquireLatestImage();
            ByteBuffer buffer = image.getPlanes()[0].getBuffer();
            byte[] bytes = new byte[buffer.capacity()];
            buffer.get(bytes);
            try {
                save(bytes);
            } catch (IOException e) {
                e.printStackTrace();
            }finally {
                if (image != null){
                    image.close();
                }
            }

        }
    };

    reader.setOnImageAvailableListener(readerListener,mBackgroundHandler);

    final CameraCaptureSession.CaptureCallback captureListener = new CameraCaptureSession.CaptureCallback() {
        @Override
        public void onCaptureCompleted(CameraCaptureSession session,CaptureRequest request,TotalCaptureResult result) {
            super.onCaptureCompleted(session, request, result);
            Toast.makeText(getApplicationContext(),"Saved",Toast.LENGTH_SHORT).show();
            try {
                createCameraPreview();
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }

        }
    };

    cameraDevice.createCaptureSession(outputSurfaces, new CameraCaptureSession.StateCallback() {
        @Override
        public void onConfigured(CameraCaptureSession session) {
            Toast.makeText(getApplicationContext(),"On Config 2",Toast.LENGTH_SHORT).show();
            try {
                session.capture(captureBuilder.build(),captureListener,mBackgroundHandler);
            } catch (CameraAccessException e) {
                e.printStackTrace();
            }

        }

        @Override
        public void onConfigureFailed(CameraCaptureSession session) {
            Toast.makeText(getApplicationContext(),"Error",Toast.LENGTH_SHORT).show();

        }
    },mBackgroundHandler);

}

private void save(byte[] bytes) throws IOException {
    OutputStream outputStream = null;
    outputStream = new FileOutputStream(file);
    outputStream.write(bytes);
    outputStream.close();
}

@Override
protected void onResume() {
    super.onResume();
    startBackgroundThread();

    if (textureView.isAvailable()){
        try {
            openCamera();
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }
    else {
        textureView.setSurfaceTextureListener(textureListener);
    }

}

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

@Override
protected void onPause() {
    try {
        stopBackgroundThread();
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    super.onPause();
}

protected void stopBackgroundThread() throws InterruptedException {
    mBackgroundThread.quitSafely();
    mBackgroundThread.join();
    mBackgroundThread = null;
    mBackgroundHandler = null;
}
}

当它运行时，它似乎没有输入onImageAvailable方法，我相信这是问题所在，但是由于我对如何利用此API尚不了解，所以我不确定100％是否是问题所在。