效果图

Untitled.gif

核心代码

UITouch *touch = [touches anyObject];
    CGPoint currentPosition = [touch locationInView:self];
    //偏移量
    float offsetX = currentPosition.x - beginpoint.x;
    float offsetY = currentPosition.y - beginpoint.y;
    //移动后的中心坐标
    CGPoint  point =CGPointMake(self.center.x + offsetX, self.center.y + offsetY); 
    //最大centX
    CGFloat maxCenterX =main_width-self.frame.size.width*0.5+40;
    //最小centX
    CGFloat minCenterX =self.frame.size.width*0.5; 
    CGFloat  miniCenterY =self.frame.size.height*0.5+60;
    CGFloat  maxCenterY =main_height-self.frame.size.height*0.5-40;
   
    if( point.x>=minCenterX && point.x <=maxCenterX  && point.y>= miniCenterY && point.y<= maxCenterY){
    
        self.center = point;
    }