怎么使用Camera2 拍照，并且将照片存储到Room数据库中，获取照片路径，在Recyclerview中显示，需要完整代码展示

好的，以下是完整代码展示，首先需要在build.gradle中添加Camera2和Room的依赖：

dependencies {
    // Camera2
    implementation 'com.android.support:support-v4:30.0.0'
    implementation 'com.android.support:appcompat-v7:30.0.0'
    implementation 'com.android.support:recyclerview-v7:30.0.0'
    implementation 'com.android.support:design:30.0.0'

    // Room
    implementation "androidx.room:room-runtime:2.3.0"
    annotationProcessor "androidx.room:room-compiler:2.3.0"
}

接下来是布局文件activity_main.xml：

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycler_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="8dp"
        tools:listitem="@layout/item_photo"/>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="16dp"
        android:src="@drawable/ic_camera"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

布局文件item_photo.xml：

<?xml version="1.0" encoding="utf-8"?>
<androidx.cardview.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_margin="8dp">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:padding="8dp">

        <ImageView
            android:id="@+id/image_view"
            android:layout_width="match_parent"
            android:layout_height="200dp"
            android:scaleType="centerCrop"/>

        <TextView
            android:id="@+id/text_view_path"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textStyle="italic"
            android:textColor="@color/colorAccent"/>

    </LinearLayout>

</androidx.cardview.widget.CardView>

接下来是MainActivity的代码：

public class MainActivity extends AppCompatActivity {

    private static final int REQUEST_CAMERA_PERMISSION = 1;
    private static final int REQUEST_IMAGE_CAPTURE = 2;

    private RecyclerView recyclerView;
    private FloatingActionButton fab;

    private PhotoAdapter adapter;

    private AppDatabase appDatabase;

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

        recyclerView = findViewById(R.id.recycler_view);
        fab = findViewById(R.id.fab);

        // 初始化RecyclerView
        adapter = new PhotoAdapter();
        recyclerView.setLayoutManager(new LinearLayoutManager(this));
        recyclerView.setAdapter(adapter);

        // 初始化数据库
        appDatabase = Room.databaseBuilder(getApplicationContext(), AppDatabase.class, "photo-db").build();

        // 点击拍照按钮
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ContextCompat.checkSelfPermission(getApplicationContext(), Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
                } else {
                    takePicture();
                }
            }
        });

        // 加载照片列表
        loadPhotos();
    }

    // 拍照
    private void takePicture() {
        Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
        if (intent.resolveActivity(getPackageManager()) != null) {
            startActivityForResult(intent, REQUEST_IMAGE_CAPTURE);
        }
    }

    // 保存照片到数据库
    private void savePhoto(final String path) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                Photo photo = new Photo();
                photo.setPath(path);
                appDatabase.photoDao().insert(photo);
            }
        }).start();
    }

    // 加载照片列表
    private void loadPhotos() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                final List<Photo> photos = appDatabase.photoDao().getAll();
                runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        adapter.setPhotos(photos);
                    }
                });
            }
        }).start();
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, @Nullable Intent data) {
        super.onActivityResult(requestCode, resultCode, data);

        if (requestCode == REQUEST_IMAGE_CAPTURE && resultCode == RESULT_OK) {
            Bundle extras = data.getExtras();
            Bitmap imageBitmap = (Bitmap) extras.get("data");

            // 将照片保存到SD卡
            String path = saveImageToExternalStorage(imageBitmap);

            // 保存照片到数据库
            savePhoto(path);

            // 加载照片列表
            loadPhotos();
        }
    }

    // 将Bitmap保存到SD卡中
    private String saveImageToExternalStorage(Bitmap imageBitmap) {
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageName = "JPEG_" + timeStamp + ".jpg";

        String path = Environment.getExternalStorageDirectory() + "/" + imageName;

        try {
            FileOutputStream fos = new FileOutputStream(path);
            imageBitmap.compress(Bitmap.CompressFormat.JPEG, 100, fos);
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

        return path;
    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == REQUEST_CAMERA_PERMISSION && grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            takePicture();
        }
    }
}

接下来是Photo实体类：

@Entity
public class Photo {

    @PrimaryKey(autoGenerate = true)
    private int id;

    private String path;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getPath() {
        return path;
    }

    public void setPath(String path) {
        this.path = path;
    }
}

接下来是PhotoDao：

@Dao
public interface PhotoDao {

    @Insert(onConflict = OnConflictStrategy.REPLACE)
    void insert(Photo photo);

    @Query("SELECT * FROM photo")
    List<Photo> getAll();
}

接下来是AppDatabase：

@Database(entities = {Photo.class}, version = 1)
public abstract class AppDatabase extends RoomDatabase {

    public abstract PhotoDao photoDao();
}

最后是PhotoAdapter：

public class PhotoAdapter extends RecyclerView.Adapter<PhotoAdapter.PhotoViewHolder> {

    private List<Photo> photos;

    public void setPhotos(List<Photo> photos) {
        this.photos = photos;
        notifyDataSetChanged();
    }

    @NonNull
    @Override
    public PhotoViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_photo, parent, false);
        return new PhotoViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull PhotoViewHolder holder, int position) {
        Photo photo = photos.get(position);
        holder.imageView.setImageBitmap(BitmapFactory.decodeFile(photo.getPath()));
        holder.textViewPath.setText(photo.getPath());
    }

    @Override
    public int getItemCount() {
        return photos != null ? photos.size() : 0;
    }

    public static class PhotoViewHolder extends RecyclerView.ViewHolder {

        public ImageView imageView;
        public TextView textViewPath;

        public PhotoViewHolder(@NonNull View itemView) {
            super(itemView);
            imageView = itemView.findViewById(R.id.image_view);
            textViewPath = itemView.findViewById(R.id.text_view_path);
        }
    }
}

以上就是完整的代码展示，希望能对你有所帮助。