Camera的使用（一）

　　本节主要记录在Android中不使用默认的拍照应用，而是自启摄像头，并不断刷新屏幕实现预览的功能。

　　AndroidManifest.xml:　　

 <activity android:name=".CameraActivity" android:screenOrientation="portrait"/>

　　CameraActivity.java:

public class CameraActivity extends Activity implements mBaseUiFragment.OnUiFragmentJumpToListener {

    CameraFragment fragment;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        //请求窗口特性：无标题
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        //添加窗口特性：全屏
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);

        super.onCreate(savedInstanceState);
        setContentView(R.layout.camera_activity_layout);
        initFragment();
    }

    private void initFragment(){
        if (fragment == null){
            fragment = new CameraFragment();
        }
        FragmentManager fragmentManager = getFragmentManager();
        FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
        fragmentTransaction.add(R.id.camera_framelayout, fragment, CameraFragment.FRAGMENT_TAG);
        fragmentTransaction.commit();
    }

    @Override
    public void jumpToFragment(Class<? extends Fragment> fragmentClass, String toFragmentTag) {

    }

    @Override
    public void jumpToFragment(Class<? extends Fragment> fragmentClass, String toFragmentTag, Bundle args) {

    }

    @Override
    public void fragmentBack() {

    }
}

　　CameraFragment.java:　　

public class CameraFragment extends mBaseUiFragment{

    static public String FRAGMENT_TAG = "CameraFragment";

    private final static int REQUEST_DELETE_PHOTO = 1;

    // 相机类
    Camera mCamera;

    //显示界面
    private SurfaceHolder mSurfaceHolder;

    // 前后摄像头的选择
    private int switchCamera = 1;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setRetainInstance(true);
    }

    @Nullable
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        rootView = inflater.inflate(R.layout.camera_layout, null);
        initView();

        return rootView;
    }

    private void initView(){
        SurfaceView mSurfaceView = (SurfaceView) rootView.findViewById(R.id.camera_surfaceView);
        mSurfaceHolder = mSurfaceView.getHolder();
        mSurfaceHolder.addCallback(
                new SurfaceHolder.Callback() {
                    @Override
                    public void surfaceCreated(SurfaceHolder holder) {
                        //当SurfaceView的视图层级结构被放到屏幕上时候，连接Camera和Surface
                        try {

                            if (mCamera != null) {
                                mCamera.setPreviewDisplay(holder);
                            }

                        } catch (Exception e) {
                            // TODO: handle exception
                        }
                    }

                    @Override
                    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
                        //当Surface首次显示在屏幕上时候，设置好相机参数，开始预览
                        if (mCamera == null) {
                            return;
                        }
                        Camera.Parameters parameters = mCamera.getParameters();
                        Camera.Size s = getBestSupportedSize(parameters.getSupportedPreviewSizes(), width, height);

                        parameters.setPreviewSize(s.width, s.height);

                        parameters.setPictureSize(s.width, s.height);
                        mCamera.setParameters(parameters);
                        mCamera.setDisplayOrientation(270);

                        try {
                            mCamera.startPreview();
                        } catch (Exception e) {
                            // TODO: handle exception
                            mCamera.release();
                            mCamera = null;
                        }
                    }

                    @Override
                    public void surfaceDestroyed(SurfaceHolder holder) {
                        //当视图从屏幕上移除的时候，停止预览
                        if (mCamera != null) {
                            mCamera.stopPreview();
                        }
                    }
                }
        );
    }

    /******************************************]
     *
     * 穷举法找出具有最大数目像素的尺寸
     *
     * @param sizes
     * @param width
     * @param height
     * @return
     */
    public Camera.Size getBestSupportedSize(List<Camera.Size> sizes,int width,int height) {
        Camera.Size bestSize = sizes.get(0);
        int largestArea = bestSize.width*bestSize.height;
        for (Camera.Size s :sizes) {
            int area =s.width*s.height;
            if (area > largestArea) {
                bestSize=s;
                largestArea = area;
            }
        }
        return bestSize;
    }

    @Override
    public void onPause() {
        // TODO Auto-generated method stub
        super.onPause();
        System.out.println("onPause");
        //程序中止暂停时，释放Camera
        if (mCamera!=null) {
            mCamera.release();
            mCamera=null;
        }

    }

    @SuppressLint("NewApi")
    @Override
    public void onResume() {
        // TODO Auto-generated method stub
        super.onResume();

        //程序运行时，打开Camera
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.GINGERBREAD) {
            mCamera = Camera.open(switchCamera);
        }else {
            mCamera = Camera.open();
        }

    }

}

Done