调用手机前置摄像头拍照的代码

以下是使用 Android 相机 API 调用前置摄像头拍照的代码示例：

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

private SurfaceView mSurfaceView;
private Camera mCamera;
private boolean mIsPreviewing = false;

private Camera.PictureCallback mPictureCallback = new Camera.PictureCallback() {
    @Override
    public void onPictureTaken(byte[] data, Camera camera) {
        // 在这里处理拍照后的数据
    }
};

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

    mSurfaceView = findViewById(R.id.surfaceView);
    mSurfaceView.getHolder().addCallback(new SurfaceHolder.Callback() {
        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            openCamera();
        }

        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            // 在这里设置预览尺寸等参数
        }

        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            releaseCamera();
        }
    });

    Button captureButton = findViewById(R.id.captureButton);
    captureButton.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            if (mIsPreviewing) {
                mCamera.takePicture(null, null, mPictureCallback);
            }
        }
    });
}

private void openCamera() {
    if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
            != PackageManager.PERMISSION_GRANTED) {
        ActivityCompat.requestPermissions(this,
                new String[]{Manifest.permission.CAMERA},
                REQUEST_CAMERA_PERMISSION);
        return;
    }

    mCamera = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT);
    try {
        mCamera.setPreviewDisplay(mSurfaceView.getHolder());
        mCamera.startPreview();
        mIsPreviewing = true;
    } catch (IOException e) {
        e.printStackTrace();
    }
}

private void releaseCamera() {
    if (mCamera != null) {
        mCamera.stopPreview();
        mCamera.release();
        mCamera = null;
        mIsPreviewing = false;
    }
}

@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
    if (requestCode == REQUEST_CAMERA_PERMISSION) {
        if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            openCamera();
        } else {
            // 权限被拒绝，可以在这里做一些提示
        }
    }
}

需要注意的是，上述代码只是一个示例，可能需要根据具体情况进行适当的修改。例如，需要在 AndroidManifest.xml 文件中添加相应的权限声明：

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

此外，还需要在 layout 文件中添加一个 SurfaceView 控件，用于显示相机预览图像：

<SurfaceView
    android:id="@+id/surfaceView"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

最后，记得在 AndroidManifest.xml 文件中声明该 Activity：

<activity android:name=".MainActivity" />