Android Camera2 API 拍照并保存 PNG 图片示例

在 Android 中，使用 android.hardware.camera2 包来实现相机功能。下面是一个示例的 Activity 代码，点击按钮后调用 CaptureRequest 来拍照并保存为 PNG 图片：

import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraCaptureSession;
import android.hardware.camera2.CameraDevice;
import android.hardware.camera2.CameraManager;
import android.hardware.camera2.CaptureRequest;
import android.hardware.camera2.TotalCaptureResult;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.app.ActivityCompat;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Arrays;
import java.util.Date;

public class MainActivity extends AppCompatActivity {

    private static final int REQUEST_CAMERA_PERMISSION = 200;
    private static final String TAG = "Camera2Capture";

    private Button captureButton;
    private CameraManager cameraManager;
    private CameraDevice cameraDevice;
    private CameraCaptureSession cameraCaptureSession;
    private CaptureRequest.Builder captureRequestBuilder;
    private File imageFile;

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

        captureButton = findViewById(R.id.capture_button);
        cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

        captureButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (ActivityCompat.checkSelfPermission(MainActivity.this, Manifest.permission.CAMERA) != PackageManager.PERMISSION_GRANTED) {
                    ActivityCompat.requestPermissions(MainActivity.this, new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
                    return;
                }
                try {
                    cameraManager.openCamera("0", cameraStateCallback, null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                }
            }
        });
    }

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

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

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

    private CameraCaptureSession.StateCallback captureSessionCallback = new CameraCaptureSession.StateCallback() {
        @Override
        public void onConfigured(CameraCaptureSession session) {
            cameraCaptureSession = session;
            startPreview();
        }

        @Override
        public void onConfigureFailed(CameraCaptureSession session) {
            Toast.makeText(MainActivity.this, "Failed to configure camera capture session", Toast.LENGTH_SHORT).show();
        }
    };

    private void createCaptureSession() {
        try {
            SurfaceTexture surfaceTexture = new SurfaceTexture(1);
            surfaceTexture.setDefaultBufferSize(640, 480);
            Surface previewSurface = new Surface(surfaceTexture);

            captureRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
            captureRequestBuilder.addTarget(previewSurface);

            cameraDevice.createCaptureSession(Arrays.asList(previewSurface), captureSessionCallback, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    private void startPreview() {
        try {
            cameraCaptureSession.setRepeatingRequest(captureRequestBuilder.build(), null, null);
            captureImage();
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    private void captureImage() {
        try {
            imageFile = createImageFile();
            final CaptureRequest.Builder captureBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
            captureBuilder.addTarget(ImageReader.newInstance(640, 480, ImageFormat.JPEG, 1).getSurface());
            captureBuilder.set(CaptureRequest.CONTROL_AF_MODE, CaptureRequest.CONTROL_AF_MODE_AUTO);
            captureBuilder.set(CaptureRequest.JPEG_ORIENTATION, 90);

            cameraCaptureSession.stopRepeating();
            cameraCaptureSession.abortCaptures();
            cameraCaptureSession.capture(captureBuilder.build(), captureCallback, null);
        } catch (CameraAccessException e) {
            e.printStackTrace();
        }
    }

    private File createImageFile() {
        String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
        String imageFileName = "IMG_" + timeStamp + ".png";
        File storageDir = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES);
        File imageFile = new File(storageDir, imageFileName);
        return imageFile;
    }

    private CameraCaptureSession.CaptureCallback captureCallback = new CameraCaptureSession.CaptureCallback() {
        @Override
        public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
            Toast.makeText(MainActivity.this, "Image captured: " + imageFile.getAbsolutePath(), Toast.LENGTH_SHORT).show();
            startPreview();
        }
    };

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if (requestCode == REQUEST_CAMERA_PERMISSION) {
            if (grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                try {
                    cameraManager.openCamera("0", cameraStateCallback, null);
                } catch (CameraAccessException e) {
                    e.printStackTrace();
                }
            } else {
                Toast.makeText(this, "Camera permission denied", Toast.LENGTH_SHORT).show();
            }
        }
    }
}

在你的项目中，需要在 AndroidManifest.xml 文件中添加相机权限：

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

此外，还需要添加以下权限，以便保存图片到存储中：

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

上述示例中，图片将保存在公共图片目录下，你可以根据你的需求修改保存路径。

注意：在 Android 6.0 及以上版本，你需要在运行时请求相机权限。以上示例中已包含相机权限的请求和处理逻辑。

请确保在你的设备上正确配置相机硬件，并适配正确的相机 ID（例如："0"）。