android实现前置后置摄像头相互切换

首先自定义一个继承自SurfaceView并且实现了SurfaceHolder.Callback接口的组件：

public class CameraView extends SurfaceView implements Callback {
    private SurfaceHolder surfaceHolder;
    private Camera mCamera;

    public CameraView(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public void init(Camera camera){
        surfaceHolder = getHolder();
        surfaceHolder.addCallback(this);
        mCamera = camera;
    }
    
    /**
     * 初始化SurfaceView时调用一次，另外更改surface或者onpause->onresume时调用
     */
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        if(holder.getSurface() == null || mCamera == null){
            return;
        }
        mCamera.stopPreview();
        try {
            mCamera.setPreviewDisplay(surfaceHolder);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        mCamera.startPreview();
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        if(mCamera == null){
            return;
        }
        try {
            mCamera.setPreviewDisplay(surfaceHolder);
        } catch (IOException e) {
            e.printStackTrace();
        }
        mCamera.startPreview();

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // TODO Auto-generated method stub
    }
}

检查设备是否有摄像头：

private boolean checkCamera(){
    return MainActivity.this.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA);
}

标记前置，后置摄像头，以及当前打开的摄像头，并且首先默认打开前置摄像头，监听Button的click事件，切换摄像头：

public class MainActivity extends Activity {
    private Button button;
    private Camera camera;
    private CameraView cameraView;
    private static final int FRONT = 1;//前置摄像头标记
    private static final int BACK = 2;//后置摄像头标记
    private int currentCameraType = -1;//当前打开的摄像头标记
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        if(!checkCamera()){
            MainActivity.this.finish();
        }
        try {
            camera = openCamera(FRONT);
        } catch (Exception e) {
            e.printStackTrace();
        }
        button = (Button)findViewById(R.id.button);
        button.setOnClickListener(new Button.OnClickListener() {
            @Override
            public void onClick(View v) {
                try {
                    changeCamera();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        });
        cameraView = (CameraView)findViewById(R.id.cameraview);
        cameraView.init(camera);
    }
    
    /**
     * @return 摄像头是否存在
     */
    private boolean checkCamera(){
        return MainActivity.this.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA);
    }
    
    @SuppressLint("NewApi")
    private Camera openCamera(int type){
        int frontIndex =-1;
        int backIndex = -1;
        int cameraCount = Camera.getNumberOfCameras();
        CameraInfo info = new CameraInfo();
        for(int cameraIndex = 0; cameraIndex<cameraCount; cameraIndex++){
            Camera.getCameraInfo(cameraIndex, info);
            if(info.facing == CameraInfo.CAMERA_FACING_FRONT){
                frontIndex = cameraIndex;
            }else if(info.facing == CameraInfo.CAMERA_FACING_BACK){
                backIndex = cameraIndex;
            }
        }
        
        currentCameraType = type;
        if(type == FRONT && frontIndex != -1){
            return Camera.open(frontIndex);
        }else if(type == BACK && backIndex != -1){
            return Camera.open(backIndex);
        }
        return null;
    }
    
    private void changeCamera() throws IOException{
        camera.stopPreview();
        camera.release();
        if(currentCameraType == FRONT){
            camera = openCamera(BACK);
        }else if(currentCameraType == BACK){
            camera = openCamera(FRONT);
        }
        camera.setPreviewDisplay(cameraView.getHolder());
        camera.startPreview();
    }
}

布局文件：

<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"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/switchcamera" />
    
    <com.example.cameratest.CameraView
        android:id="@+id/cameraview"
        android:layout_below="@id/button"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"/>
</RelativeLayout>

当然，首先得申明权限跟软硬件环境：

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

最好把activity的screenOrientation设置为landscape，不然显示的方向不对。

如果有可以优化的地方，望各位大侠指导，谢谢。