iOS使用加速度计在圆圈内移动对象

概述我正在尝试使用加速度计在圆圈内移动图像.我有一个问题,当图像碰到圆的边缘时,它只是移动圆的另一边.我的代码如下： - (void)accelerometer:(UIAccelerometer *)accelerometer didAccelerate:(UIAcceleration *)acceleration {//NSLog(@"x : %g", acceleration.x);//NSL 我正在尝试使用加速度计在圆圈内移动图像.我有一个问题,当图像碰到圆的边缘时,它只是移动圆的另一边.我的代码如下：

- (voID)accelerometer:(UIAccelerometer *)accelerometer dIDAccelerate:(UIacceleration *)acceleration {//NSLog(@"x : %g",acceleration.x);//NSLog(@"y : %g",acceleration.y);//NSLog(@"z : %g",acceleration.z);delta.x = acceleration.x * 10;delta.y = acceleration.y * 10;joypadCap.center = CGPointMake(joypadCap.center.x + delta.x,joypadCap.center.y - delta.y);distance = sqrtf(((joypadCap.center.x - 160) * (joypadCap.center.x - 160)) +                 ((joypadCap.center.y -206) * (joypadCap.center.y - 206)));//NSLog(@"distance : %f",distance);touchAngle = atan2(joypadCap.center.y,joypadCap.center.x);NSLog(@"Angle : %f",touchAngle);if (distance > 50) {    joypadCap.center = CGPointMake(160 - cosf(touchAngle) * 50,206 - sinf(touchAngle) * 50);}

解决方法 尝试使用CMDeviceMotion实现循环水平仪时,我遇到了同样的问题.我发现传递给atan2(y,x)的坐标是一个问题.此功能需要笛卡尔坐标,视图中心有(0,0).但是,屏幕坐标左上角有(0,0).我创建了在两个坐标系之间转换点的方法,现在它运行良好.

我在github上设置了一个示例项目here,但这是最重要的部分：

float distance = sqrtf(((point.x - halfOfWIDth) * (point.x - halfOfWIDth)) +                       ((point.y - halfOfWIDth) * (point.y - halfOfWIDth)));if (distance > maxdistance){    // Convert point from screen coordinate system to cartesian coordinate system,// with (0,0) located in the centre of the vIEw    CGPoint pointInCartesianCoordSystem = [self convertScreenPointToCartesianCoordSystem:point                                                                                 inFrame:self.vIEw.frame];    // Calculate angle of point in @R_419_4741@ from centre of the vIEw    CGfloat angle = atan2(pointInCartesianCoordSystem.y,pointInCartesianCoordSystem.x);    // Get new point on the edge of the circle    point = CGPointMake(cos(angle) * maxdistance,sinf(angle) * maxdistance);    // Convert back to screen coordinate system    point = [self convertCartesianPointToScreenCoordSystem:point inFrame:self.vIEw.frame];}

和：

- (CGPoint)convertScreenPointToCartesianCoordSystem:(CGPoint)point                                            inFrame:(CGRect)frame{    float x = point.x - (frame.size.wIDth / 2.0f);    float y = (point.y - (frame.size.height / 2.0f)) * -1.0f;    return CGPointMake(x,y);}- (CGPoint)convertCartesianPointToScreenCoordSystem:(CGPoint)point                                            inFrame:(CGRect)frame{    float x = point.x + (frame.size.wIDth / 2.0f);    float y = (point.y * -1.0f) + (frame.size.height / 2.0f);    return CGPointMake(x,y);}

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