Camera 拍照

本文探讨了如何在Android中使用Camera进行拍照,并强调了代码重构的重要性。通过介绍背景、方法和实例,展示了从MainActivity中抽取Camera相关代码到CameraEngine类的过程,以实现更清晰的代码组织和管理。

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1、背景

同样这篇文章是为了练习代码的抽取能力,其实Camera的拍照后我们会获取到原始照片的数据,这些数据我们可以进行处理;比如加个滤镜,美白等等;这就是我们的美白相机了,但对于图片的处理,我们最好在底层处理;然后把处理的图片数据再转换成图片,最后展示给用户,美白相机的大体流程就是这样的,不过今天主要练习代码的抽取能力;虽然上次已经写过了,只有经过反复的训练,我们才能对怎样抽取代码,并进行封装得心用手;

2、方法(来自疯狂Androud讲义)

Android应用提供了Camera来控制拍照,使用Camera进行拍照比较简单,按如下步骤进行即可。
1:调用Camera的open()方法打开相机。该方法默认打开后置摄像头。如果需要打开指定摄像头,可以为该方法传入声响头ID.
2:调用Camera的getParameters()方法获取拍照参数,该方法返回一个Camera.Parameters对象。
3:调用Camera.Parameters对象方法设置拍照参数;
4:调用Camera的startPreview()方法开始预览取景,在预览取景之前调用Camera的setPreviewDisplay(SurfaceViewHolder holder)方法设置使用哪个SurfaceView来显示取景图片。
5:调用Camera的takePicture()方法进行拍照。
6:结束程序时,调用Camera的stopPreview()结束取景预览,并调用release()方法释放资源;

3、实例

该实例通过预览,当我们点击拍照后,会弹出一个对话框,让用户输入图片的名字;

1、MainActivity布局:
<RelativeLayout 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"
    tools:context=".MainActivity" >
    <SurfaceView 
        android:id="@+id/surfaceView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        />
    <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:gravity="center_horizontal"
        android:layout_marginBottom="8dp"
        >
        <Button 
            android:id="@+id/btn_capture"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:background="@drawable/normal_capture"
            />
    </LinearLayout>
</RelativeLayout>

2、对话框布局:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >
    <LinearLayout 
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal"
        android:padding="5dp"
        >
        <TextView 
            android:layout_width="0dp"
            android:layout_weight="1"
            android:layout_height="wrap_content"
            android:text="文件名:"
            android:textSize="20sp"
            />
        <EditText 
            android:id="@+id/et_filename"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            />
    </LinearLayout>
    <ImageView 
        android:id="@+id/iv_picture"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:scaleType="fitCenter"
        />
</LinearLayout>
3、MainActivity代码:
public class MyActivity01 extends Activity implements SurfaceHolder.Callback,OnClickListener{

    private SurfaceView surfaceView;
    private Button ib_capture;
    private Camera mCamera;
    private int screenWidth;
    private int screenHeight;
    private boolean isPreview = false;

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

    private void initData() {
        DisplayMetrics outMetrics = new DisplayMetrics();
        getWindowManager().getDefaultDisplay().getMetrics(outMetrics);;
        screenWidth = outMetrics.widthPixels;
        screenHeight = outMetrics.heightPixels;
    }

    private void initView() {
        surfaceView =  (SurfaceView) this.findViewById(R.id.surfaceView);
        surfaceView.getHolder().setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        surfaceView.getHolder().addCallback(this);
        ib_capture = (Button) this.findViewById(R.id.btn_capture);
        ib_capture.setOnClickListener(this);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {

    }
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        initCamera();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        if(null != mCamera){
            if(isPreview)
                mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }
    }

    @Override
    public void onClick(View v) {
        if(null != mCamera){
            mCamera.autoFocus(new MyAutoFocusCallback());
        }
    }

    private void initCamera() {
        if(!isPreview){
            mCamera = Camera.open();
            mCamera.setDisplayOrientation(90);
        }
        if(null != mCamera && !isPreview){
            try {
                //设置surfaceView的取景画面
                mCamera.setPreviewDisplay(surfaceView.getHolder());
                Parameters mParameters = mCamera.getParameters();
                //设置预览照片的大小
                mParameters.setPreviewSize(screenWidth, screenHeight);
                //设置预览照片时每秒显示多少帧的最大值、最小值
                mParameters.setPreviewFpsRange(4, 10);
                //设置图片格式JPEG
                mParameters.setPictureFormat(ImageFormat.JPEG);
                //设置照片的质量
                mParameters.setJpegQuality(88);
                //设置照片的大小
                mParameters.setPictureSize(screenWidth, screenHeight);
                //开始预览
                mCamera.startPreview();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        isPreview = true;
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        if(null != mCamera){
            if(isPreview)
                mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }
    }

    private final class MyAutoFocusCallback implements AutoFocusCallback{

        @Override
        public void onAutoFocus(boolean success, Camera camera) {
            if(success){
                camera.takePicture(new ShutterCallback() {

                    @Override
                    public void onShutter() {
                        //按下快门瞬间执行此处代码
                    }
                }, new PictureCallback() {

                    @Override
                    public void onPictureTaken(byte[] data, Camera camera) {
                        //此处代码可以决定是否需要保存原始照片信息
                    }
                },  new MyPictureCallback());
            }
        }
    }
    private final class MyPictureCallback implements PictureCallback{
        //通过该方法获取JPEG照片,通过对话框的形式提示给用户,并让用户给起名,然后保存;
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            final Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
            View view = View.inflate(MainActivity.this, R.layout.dialog_view, null);
            ImageView mImageView = (ImageView) view.findViewById(R.id.iv_picture);
            final EditText et_filename = (EditText) view.findViewById(R.id.et_filename);
            mImageView.setImageBitmap(bitmap);
            new AlertDialog.Builder(MainActivity.this)
                           .setView(view)
                           .setPositiveButton("保存", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog,
                                        int which) {
                                    String fileName = et_filename.getText().toString().trim();
                                    if(null != fileName || !"".equals(fileName)){
                                        try {
                                            File file = new File(Environment.getExternalStorageDirectory(),fileName+".jpeg");
                                            OutputStream outStream = new FileOutputStream(file);
                                            bitmap.compress(CompressFormat.JPEG, 100, outStream );
                                            outStream.close();
                                        } catch (Exception e) {
                                            e.printStackTrace();
                                        }
                                    }else{
                                        Toast.makeText(MainActivity.this, "文件名为空,保存失败!!!", Toast.LENGTH_LONG).show();
                                    } 
                                }
                            })
                           .setNegativeButton("取消", null)
                           .show();
            mCamera.stopPreview();
            mCamera.startPreview();
            isPreview = true;
        }

    }
} 

我们通过initView()、initData()等方法来把我们的代码逻辑清晰, 当大量的代码都放在MainActivity中时,依旧效果不是很好。
我们通过分析可以发现在MainActivity中Came的设置占据了大量代码,比如:Camera的initCamera()以及Camera拍照时设置的回调方法;所以我们可以把这些方法抽取出来,放到CameraEngine中:

4、CameraEngine类:
public class CameraEngine {
    private MainActivity context;
    private Camera mCamera;
    private int screenWidth;
    private int screenHeight;
    private boolean isPreview = false;

    public CameraEngine(Context context){
        this.context = (MainActivity) context;
        initData();
    }

    public void initData(){
        DisplayMetrics outMetrics = new DisplayMetrics();
        context.getWindowManager().getDefaultDisplay().getMetrics(outMetrics);;
        screenWidth = outMetrics.widthPixels;
        screenHeight = outMetrics.heightPixels;
    }

    public void onDestroy(){
        if(null != mCamera){
            if(isPreview)
                mCamera.stopPreview();
            mCamera.release();
            mCamera = null;
        }
    }

    public void initCamera(SurfaceView surfaceView){
        if(!isPreview){
            mCamera = Camera.open();
            mCamera.setDisplayOrientation(90);
        }
        if(null != mCamera && !isPreview){
            try {
                //设置surfaceView的取景画面
                mCamera.setPreviewDisplay(surfaceView.getHolder());
                Parameters mParameters = mCamera.getParameters();
                //设置预览照片的大小
                mParameters.setPreviewSize(screenWidth, screenHeight);
                //设置预览照片时每秒显示多少帧的最大值、最小值
                mParameters.setPreviewFpsRange(4, 10);
                //设置图片格式JPEG
                mParameters.setPictureFormat(ImageFormat.JPEG);
                //设置照片的质量
                mParameters.setJpegQuality(88);
                //设置照片的大小
                mParameters.setPictureSize(screenWidth, screenHeight);
                //开始预览
                mCamera.startPreview();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
        isPreview = true;
    }

    public void autoFocus(){
        if(null != mCamera){
            mCamera.autoFocus(new MyAutoFocusCallback());
        }
    }

    private final class MyAutoFocusCallback implements AutoFocusCallback{

        @Override
        public void onAutoFocus(boolean success, Camera camera) {
            if(success){
                camera.takePicture(new ShutterCallback() {

                    @Override
                    public void onShutter() {
                        //按下快门瞬间执行此处代码
                    }
                }, new PictureCallback() {

                    @Override
                    public void onPictureTaken(byte[] data, Camera camera) {
                        //此处代码可以决定是否需要保存原始照片信息
                    }
                },  new MyPictureCallback());
            }
        }
    }
    private final class MyPictureCallback implements PictureCallback{
        //通过该方法获取JPEG照片,通过对话框的形式提示给用户,并让用户给起名,然后保存;
        @Override
        public void onPictureTaken(byte[] data, Camera camera) {
            final Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
            View view = View.inflate(context, R.layout.dialog_view, null);
            ImageView mImageView = (ImageView) view.findViewById(R.id.iv_picture);
            final EditText et_filename = (EditText) view.findViewById(R.id.et_filename);
            mImageView.setImageBitmap(bitmap);
            new AlertDialog.Builder(context)
                           .setView(view)
                           .setPositiveButton("保存", new DialogInterface.OnClickListener() {
                                @Override
                                public void onClick(DialogInterface dialog,
                                        int which) {
                                    String fileName = et_filename.getText().toString().trim();
                                    if(null != fileName || !"".equals(fileName)){
                                        try {
                                            File file = new File(Environment.getExternalStorageDirectory(),fileName+".jpeg");
                                            OutputStream outStream = new FileOutputStream(file);
                                            bitmap.compress(CompressFormat.JPEG, 100, outStream );
                                            outStream.close();
                                        } catch (Exception e) {
                                            e.printStackTrace();
                                        }
                                    }else{
                                        Toast.makeText(context, "文件名为空,保存失败!!!", Toast.LENGTH_LONG).show();
                                    } 
                                }
                            })
                           .setNegativeButton("取消", null)
                           .show();
            mCamera.stopPreview();
            mCamera.startPreview();
            isPreview = true;
        }
    }
}
5、抽取之后的MainActivity代码:
public class MainActivity extends Activity implements SurfaceHolder.Callback,OnClickListener{

    private SurfaceView surfaceView;
    private Button ib_capture;
    private CameraEngine cameraEngine;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        cameraEngine = new CameraEngine(this);
        initView();
    }


    private void initView() {
        surfaceView =  (SurfaceView) this.findViewById(R.id.surfaceView);
        surfaceView.getHolder().setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
        surfaceView.getHolder().addCallback(this);
        ib_capture = (Button) this.findViewById(R.id.btn_capture);
        ib_capture.setOnClickListener(this);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {

    }
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        cameraEngine.initCamera(surfaceView);
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        cameraEngine.onDestroy();
    }

    @Override
    public void onClick(View v) {
        cameraEngine.autoFocus();
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        cameraEngine.onDestroy();
    }
} 

是不是很简单,MainActivity还可以更进一步的抽取;剩下的就交给你们了;

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