android调用camera时，可以自己写一个activity，赋上相关参数，打开前camera就可以了；

需要申请的permission，在AndroidManifest.xml中添加：

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


主要功能，打开前camera 

private Camera openFrontFacingCameraGingerbread() {
      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) {
              try {
                  cam = Camera.open(camIdx);
                  mCurrentCamIndex = camIdx;
              } catch (RuntimeException e) {
                  Log.e(TAG, "Camera failed to open: " + e.getLocalizedMessage());
              }
          }
      }

      return cam;
  }


根据打开时的横竖屏方向来调整preview角度 

//根据横竖屏自动调节preview方向，Starting from API level 14, this method can be called when preview is active.
  private static void setCameraDisplayOrientation(Activity activity,int cameraId, Camera camera) 
  {    
       Camera.CameraInfo info = new Camera.CameraInfo(); 
         Camera.getCameraInfo(cameraId, info);      
         int rotation = activity.getWindowManager().getDefaultDisplay().getRotation();

         //degrees  the angle that the picture will be rotated clockwise. Valid values are 0, 90, 180, and 270. 
         //The starting position is 0 (landscape). 
         int degrees = 0;
         switch (rotation) 
         {   
             case Surface.ROTATION_0: degrees = 0; break;         
             case Surface.ROTATION_90: degrees = 90; break;    
             case Surface.ROTATION_180: degrees = 180; break; 
             case Surface.ROTATION_270: degrees = 270; break;  
          }      
         int result;  
         if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT)
         {        
             result = (info.orientation + degrees) % 360;     
             result = (360 - result) % 360;  // compensate the mirror   
         } 
         else 
         {  
         // back-facing       
            result = (info.orientation - degrees + 360) % 360;   
         }     
         camera.setDisplayOrientation(result);  
  }