如何利用Android系统实现摄像头拍照功能？

在Android应用开发中，调用摄像头进行拍照功能是一个常见的需求，本文将详细介绍如何在Android应用中实现这一功能，包括权限申请、相机启动、拍照处理以及图片保存等步骤。

一、权限申请

在Android 6.0（API级别23）及以上版本中，需要在运行时请求用户授予相机和存储权限，在AndroidManifest.xml文件中声明所需权限：

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

在代码中动态请求权限：

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

二、相机启动

创建相机实例并启动预览：

private Camera mCamera;
private CameraPreview mPreview;
private void openCamera() {
    mCamera = getCameraInstance();
    mPreview = new CameraPreview(this, mCamera);
    FrameLayout preview = findViewById(R.id.camera_preview);
    preview.addView(mPreview);
}
private Camera getCameraInstance() {
    CameraCharacteristics characteristics = null;
    CameraManager manager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
    try {
        String cameraId = manager.getCameraIdList()[0]; // 使用后置摄像头
        characteristics = manager.getCameraCharacteristics(cameraId);
        StreamConfigurationMap map = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
        assert map != null;
        Size largest = Collections.max(Arrays.asList(map.getOutputSizes(ImageFormat.YUV_420_888)), new CompareSizesByArea());
        mCamera = manager.openCamera(cameraId, stateCallback, null);
    } catch (CameraAccessException e) {
        e.printStackTrace();
    }
    return mCamera;
}

三、拍照处理

设置拍照按钮点击事件监听器，捕获拍照瞬间：

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

定义回调接口处理拍照结果：

private final ImageReader.OnImageAvailableListener mPicture = new ImageReader.OnImageAvailableListener() {
    @Override
    public void onImageAvailable(ImageReader reader) {
        Bitmap bitmap = mBitmap;
        File pictureFile = getOutputMediaFile();
        if (pictureFile == null) {
            return;
        }
        try (FileOutputStream fos = new FileOutputStream(pictureFile)) {
            bitmap.compress(Bitmap.CompressFormat.JPEG, QUALITY, 100, fos);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
};

四、图片保存

定义方法生成唯一的文件名并保存图片：

private File getOutputMediaFile() {
    File mediaStorageDir = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES), "MyCameraApp");
    if (!mediaStorageDir.exists()) {
        if (!mediaStorageDir.mkdirs()) {
            return null;
        }
    }
    String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
    File mediaFile; = new File(mediaStorageDir.getPath() + File.separator + "IMG_"+ timeStamp +".jpg");
    return mediaFile;
}

五、完整代码示例

以下是完整的代码示例，展示了如何在Android应用中实现调用摄像头进行拍照功能：

public class MainActivity extends AppCompatActivity {
    private static final int PERMISSION_REQUEST_CODE = 100;
    private Camera mCamera;
    private CameraPreview mPreview;
    private final ImageReader.OnImageAvailableListener mPicture = new ImageReader.OnImageAvailableListener() {
        @Override
        public void onImageAvailable(ImageReader reader) {
            Bitmap bitmap = mBitmap;
            File pictureFile = getOutputMediaFile();
            if (pictureFile == null) {
                return;
            }
            try (FileOutputStream fos = new FileOutputStream(pictureFile)) {
                bitmap.compress(Bitmap.CompressFormat.JPEG, QUALITY, 100, fos);
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    };
    // ...其他代码...
}

到此，以上就是小编对于“Android实现调用摄像头进行拍照功能”的问题就介绍到这了，希望介绍的几点解答对大家有用，有任何问题和不懂的，欢迎各位朋友在评论区讨论，给我留言。