使用Camera API在Android上切换摄像头

Question

Hello there我是Camera API的newbiew。我正在向我自己学习！我只是想切换我的相机后台和前台！ 我的设备有前后相机！ 我这样做，如：

---

public class CameraFrag extends Fragment { 

//Variables 
private Camera mCamera; 
private CameraPreview mPreview; 
private ToggleButton flipCamera; 
//////////////////////////////////// 

public CameraFrag() { 
} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 
    //inflate the layout 
    View v = inflater.inflate(R.layout.frag, container, false); 

    flipCamera = (ToggleButton) v.findViewById(R.id.flipper); 

    // Create an instance of Camera 
    mCamera = getCameraInstance(); 

    // Create our Preview view and set it as the content of our activity. 
    mPreview = new CameraPreview(getContext(), mCamera); 
    FrameLayout preview = (FrameLayout) v.findViewById(R.id.camera_preview); 
    preview.addView(mPreview); 

    flipCamera.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() { 
     @Override 
     public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) { 
      // TODO Auto-generated method stub 
      try{ 
       mCamera.stopPreview(); 

       if(isChecked){ 
        mCamera=openFrontFacingCamera(); 
       } 
       else{ 
        mCamera=openBackFacingCamera(); 
       } 
       mCamera.startPreview(); 
      }catch(Exception exp){ 
       Log.i("#LOGTAG","EXCEPTION "+exp); 
      } 
     } 
    }); 

    return v; 
} 

private Camera openBackFacingCamera() { 
    int cameraCount = 0; 
    Camera cam = null; 
    Camera.CameraInfo cameraInfo = new Camera.CameraInfo(); 
    cameraCount = Camera.getNumberOfCameras(); 
    for (int camIdx = 0; camIdx < cameraCount; camIdx++) { 
     Camera.getCameraInfo(camIdx, cameraInfo); 
     if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_BACK) { 
      cam = Camera.open(camIdx); 
     } 
    } 

    return cam; 
} 

private Camera openFrontFacingCamera() { 
    int cameraCount = 0; 
    Camera cam = null; 
    Camera.CameraInfo cameraInfo = new Camera.CameraInfo(); 
    cameraCount = Camera.getNumberOfCameras(); 
    for (int camIdx = 0; camIdx < cameraCount; camIdx++) { 
     Camera.getCameraInfo(camIdx, cameraInfo); 
     if (cameraInfo.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) { 
      cam = Camera.open(camIdx); 
     } 
    } 

    return cam; 
} 

/** A safe way to get an instance of the Camera object. */ 
public static Camera getCameraInstance(){ 
    Camera c = null; 
    try { 
     c = Camera.open(); // attempt to get a Camera instance 
    } 
    catch (Exception e){ 
     // Camera is not available (in use or does not exist) 
    } 
    return c; // returns null if camera is unavailable 
} 

}

---

的问题是，它总是抛出异常如：

I /＃LOGTAG：EXCEPTION的Java。 lang.RuntimeException：无法连接到相机服务

---

，如果我用我的代码为：

   try{ 
       mCamera.stopPreview(); 
       mCamera.release(); 
       if(isChecked){ 
        mCamera=openFrontFacingCamera(); 
       } 
       else{ 
        mCamera=openBackFacingCamera(); 
       } 
       mCamera.startPreview(); 
      }catch(Exception exp){ 
       Log.i("#LOGTAG","EXCEPTION "+exp); 
      } 

我的预览冻结，回来时，我点击后退按钮！

---

我在做什么错了？这是在相机之间切换的正确方法吗？有人可以帮我吗？

在此先感谢！

Answer 1

只需打开这样所需的摄像机：

对于前置摄像头：

c = Camera.open(Camera.CameraInfo.CAMERA_FACING_FRONT); 

对于相机背面：

c = Camera.open(Camera.CameraInfo.CAMERA_FACING_BACK); 

，并确保你总是释放你的相机，当你完成或在您的片段的onPause方法使用以下代码否则相机实例将永远不会被释放，甚至您的主相机应用程序将无法获得它。

private void releaseCameraAndPreview() { 
    if (mCamera != null) { 
     mCamera.stopPreview(); 
     mCamera.release(); 
     mCamera = null; 
    } 
}