如何利用Android开发实现拍照功能？

在Android开发中，实现拍照功能是一项常见且重要的技能，本文将详细介绍如何在Android应用中实现拍照功能，包括检查设备是否有摄像头、初始化相机、设置预览界面、实现自动对焦及拍照后保存图片到SD卡的方法，以下是具体步骤和代码示例：

检查设备是否有摄像头

需要检查设备是否具备摄像头功能，这可以通过调用系统服务PackageManager来实现。

private boolean checkCameraHardware(Context context) {
    if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
        return true;
    }
    return false;
}

初始化相机

通过调用Camera.open(0)方法来初始化相机，这里的参数0表示使用后置摄像头。

public static Camera getCamera() {
    Camera camera = null;
    try {
        camera = Camera.open(0);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return camera;
}

设置预览界面

为了显示相机的实时画面，需要创建一个预览界面，这里我们使用SurfaceView来实现。

@SuppressWarnings("deprecation")
private class SurfacePreView extends SurfaceView implements SurfaceHolder.Callback {
    private Camera mCamera;
    private SurfaceHolder mHolder;
    public SurfacePreView(Context context, Camera camera) {
        super(context);
        mCamera = camera;
        mHolder = getHolder();
        mHolder.addCallback(this);
        mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
    }
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
        if (holder.getSurface() == null) {
            return;
        }
        try {
            mCamera.stopPreview();
            mCamera.setPreviewDisplay(mHolder);
            mCamera.startPreview();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // Take care of releasing the Camera preview in your implementation
        mCamera = null;
    }
}

实现拍照功能

当用户点击拍照按钮时，调用相机的autoFocus方法进行对焦，然后调用takePicture方法拍摄照片。

public void takephoto(View view) {
    mCamera.autoFocus(new AutoFocusCallback() {
        @Override
        public void onAutoFocus(boolean success, Camera camera) {
            mCamera.takePicture(null, null, mPicture);
        }
    });
}

拍照后的图片保存

拍摄完成后，通过实现PictureCallback接口来处理拍摄得到的图片数据，并将其保存到SD卡中。

private PictureCallback mPicture = new PictureCallback() {
    @Override
    public void onPictureTaken(byte[] data, Camera camera) {
        try {
            File file = new File("/sdcard/file/aa.jpg");
            if (!file.exists()) {
                file.mkdirs();
            }
            FileOutputStream fos = new FileOutputStream(file);
            fos.write(data);
            fos.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
};

完整代码示例

以下是一个完整的Activity代码示例，展示了如何集成上述所有步骤：

public class CameraActivity extends Activity {
    private Camera mCamera;// 相机
    private SurfacePreView mPreView;// 视图
    private FrameLayout mFrameLayout;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_camera_takephoto);
        mFrameLayout = (FrameLayout) findViewById(R.id.framelayout);
        if (checkCameraHardware(this)) {
            mCamera = getCamera();
            mPreView = new SurfacePreView(this, mCamera);
            mFrameLayout.addView(mPreView);
        }
    }
    /**
     * 拍照对焦
     * @param view
     */
    public void takephoto(View view){
        mCamera.autoFocus(new AutoFocusCallback() {
            @Override
            public void onAutoFocus(boolean success, Camera camera) {
                mCamera.takePicture(null, null, mPicture);
            }
        });
    }
    /**
     * 拍照后的图片保存
     */
    private PictureCallback mPicture = new PictureCallback() {
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            try {
                File file = new File("/sdcard/file/aa.jpg");
                if (!file.exists()) {
                    file.mkdirs();
                }
                FileOutputStream fos = new FileOutputStream(file);
                fos.write(data);
                fos.close();
            } catch (FileNotFoundException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    };
    /**
     * 判断照相机是否存在
     * @param context
     * @return
     */
    private boolean checkCameraHardware(Context context){
        if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
            return true;
        }
        return false; 
    }
    /**
     * 初始化照相机
     * @return
     */
    public static Camera getCamera(){
        Camera camera = null;
        try {
            camera = Camera.open(0);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return camera;
    }
    /**
     * 实现拍照视图
     */
    @SuppressWarnings("deprecation")
    private class SurfacePreView extends SurfaceView implements SurfaceHolder.Callback{
        private Camera mCamera;
        private SurfaceHolder mHolder;
        public SurfacePreView(Context context, Camera camera) {
            super(context);
            mCamera = camera;
            mHolder = getHolder();
            mHolder.addCallback(this);
            mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        }
        @Override
        public void surfaceCreated(SurfaceHolder holder) {
            try {
                mCamera.setPreviewDisplay(mHolder);
                mCamera.startPreview();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        @Override
        public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
            if (holder.getSurface() == null) {
                return;
            }
            try {
                mCamera.stopPreview();
                mCamera.setPreviewDisplay(mHolder);
                mCamera.startPreview();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        @Override
        public void surfaceDestroyed(SurfaceHolder holder) {
            // Take care of releasing the Camera preview in your implementation
            mCamera = null;
        }
    }
}

相关问题与解答栏目：

问题1：如何在Android中调用系统自带的摄像头进行拍照？

答案： 调用系统自带摄像头进行拍照可以通过启动一个意图（Intent）来实现，在AndroidManifest.xml文件中添加必要的权限声明： ``xml <uses-permission android:name="android.permission.CAMERA" /> <uses-feature android:name="android.hardware.camera" /> <uses-feature android:name="android.hardware.camera.autofocus" />` 在主类Java文件中加入以下代码：`java final int TAKE_PICTURE = 1; //定义请求码 startActivityForResult(new Intent("android.media.action.IMAGE_CAPTURE"), TAKE_PICTURE);` 处理拍照得到的数据并保存下来：`java protected void onActivityResult(int requestCode, int resultCode, Intent data) { if (requestCode == TAKE_PICTURE && resultCode == RESULT_OK) { Bitmap bm = (Bitmap) data.getExtras().get("data"); ImageView img = (ImageView) findViewById(R.id.imageView); img.setImageBitmap(bm); File myCaptureFile = new File("sdcard/123456.jpg"); try { BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(myCaptureFile)); /*采用压缩转档方法*/ bm.compress(Bitmap.CompressFormat.JPEG, 80, bos); /*调用flush()方法，更新BufferStream*/ bos.flush(); /*结束OutputStream*/ bos.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } }}`问题2：如何在拍照后直接显示图片到ImageView上？`java protected void onActivityResult(int requestCode, int resultCode, Intent data) { if (requestCode == TAKE_PICTURE && resultCode == RESULT_OK) { Bitmap bm = (Bitmap) data.getExtras().get("data"); ImageView img = (ImageView) findViewById(R.id.imageView); img.setImageBitmap(bm); //保存图片到SD卡的逻辑可以在这里添加，如上一个问题的答案所示}}``

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