Improve camera javadoc and fix some errors.

    // outside the current field of view, even when using zoom.

    //

    // Focus area only has effect if the current focus mode is FOCUS_MODE_AUTO,

    // FOCUS_MODE_MACRO, or FOCUS_MODE_CONTINOUS_VIDEO.

    // FOCUS_MODE_MACRO, FOCUS_MODE_CONTINUOUS_VIDEO, or

    // FOCUS_MODE_CONTINUOUS_PICTURE.

    // Example value: "(-10,-10,0,0,300),(0,0,10,10,700)". Read/write.

    static const char KEY_FOCUS_AREAS[];

    // Focal length in millimeter.

    // recording because the focus changes smoothly . Applications still can

    // call CameraHardwareInterface.takePicture in this mode but the subject may

    // not be in focus. Auto focus starts when the parameter is set.

    // Applications should not call CameraHardwareInterface.autoFocus in this

    // mode. To stop continuous focus, applications should change the focus mode

    // to other modes.

    //

    // Applications can call CameraHardwareInterface.autoFocus in this mode. The

    // focus callback will immediately return with a boolean that indicates

    // whether the focus is sharp or not. The focus position is locked after

    // autoFocus call. If applications want to resume the continuous focus,

    // cancelAutoFocus must be called. Restarting the preview will not resume

    // the continuous autofocus. To stop continuous focus, applications should

    // change the focus mode to other modes.

    static const char FOCUS_MODE_CONTINUOUS_VIDEO[];

    // Continuous auto focus mode intended for taking pictures. The camera

    // continuously tries to focus. The speed of focus change is more aggressive

    // than FOCUS_MODE_CONTINUOUS_VIDEO. Auto focus starts when the parameter is

    // set. If applications call autoFocus in this mode, the focus callback will

    // immediately return with a boolean that indicates the focus is sharp or

    // not. The apps can then decide if they want to take a picture immediately

    // or to change the focus mode to auto, and run a full autofocus cycle. To

    // stop continuous focus, applications should change the focus mode to other

    // modes.

    // set.

    //

    // If applications call CameraHardwareInterface.autoFocus in this mode, the

    // focus callback will immediately return with a boolean that indicates

    // whether the focus is sharp or not. The apps can then decide if they want

    // to take a picture immediately or to change the focus mode to auto, and

    // run a full autofocus cycle. The focus position is locked after autoFocus

    // call. If applications want to resume the continuous focus,

    // cancelAutoFocus must be called. Restarting the preview will not resume

    // the continuous autofocus. To stop continuous focus, applications should

    // change the focus mode to other modes.

    static const char FOCUS_MODE_CONTINUOUS_PICTURE[];

private: