从此加速度计代码中删除垂直移动？

Question

在此代码中，我想删除垂直移动（我不希望用户能够在屏幕上向上或向下移动uibutton，但只能向左或向右移动） 我将如何继续这样做？ 下面是代码：

- (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceration {

if (acceration.x < 0) {
    XM += 1;
    AccelPoint.x = XM;
    character.center = AccelPoint;
}
if (acceration.x > 0) {
    XM -= 1;
    AccelPoint.x = XM;
    character.center = AccelPoint;
}
if (acceration.y < 320) {
    //60
    YM += 1;
    AccelPoint.y = YM;
    character.center = AccelPoint;
}
if (acceration.y > 320) {
    //60
    YM -= 1;
    AccelPoint.y = YM;
    character.center = AccelPoint;
}
X = acceration.x*50;
XM += X;
AccelPoint.x = XM;

//58 for both

Y = acceration.y*50;
YM-= Y;
AccelPoint.y = YM;

character.center = AccelPoint;

if (AccelPoint.x < -5) {
    AccelPoint.x = -5;
}
//320
if (AccelPoint.x > 325) {
    AccelPoint.x = 325;
}
//0
character.center = AccelPoint;
if (AccelPoint.y < 0) {
    AccelPoint.y = 0;
    //15
}
if (AccelPoint.y > 240) {
    //AccelPoint.y = 240;
    //465
}

character.center = AccelPoint;

}