#import "DragerViewController.h"

#define screenW [UIScreen mainScreen].bounds.size.width

@interface DragerViewController ()

@property (nonatomic, weak) UIView *leftV;
@property (nonatomic, weak) UIView *rightV;
@property (nonatomic, weak) UIView *mainV;

@end

@implementation DragerViewController

- (void)viewDidLoad {
 [super viewDidLoad];

 //添加子控件
 [self setUp];


 //添加手势
 UIPanGestureRecognizer *pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(pan:)];

 [self.mainV addGestureRecognizer:pan];


 //给控制器的View添加点按手势
 UITapGestureRecognizer *tap = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(tap)];
 [self.view addGestureRecognizer:tap];
}

- (void)tap{
 //让MainV复位

 [UIView animateWithDuration:0.5 animations:^{
 self.mainV.frame = self.view.bounds;
 }];

}



#define targetR 275
#define targetL -275
- (void)pan:(UIPanGestureRecognizer *)pan{

 //获取偏移量
 CGPoint transP = [pan translationInView:self.mainV];
 //为什么不使用transform,是因为我们还要去修改高度,使用transform,只能修改,x,y
 //self.mainV.transform = CGAffineTransformTranslate(self.mainV.transform, transP.x, 0);

 self.mainV.frame = [self frameWithOffsetX:transP.x];
 //判断拖动的方向
 if(self.mainV.frame.origin.x > 0){
 //向右
 self.rightV.hidden = YES;
 }else if(self.mainV.frame.origin.x < 0){
 //向左
 self.rightV.hidden = NO;
 }

 //当手指松开时,做自动定位.
 CGFloat target = 0;
 if (pan.state == UIGestureRecognizerStateEnded) {

 if (self.mainV.frame.origin.x > screenW * 0.5 ) {
  //1判断在右侧
  //当前View的x有没有大于屏幕宽度的一半,大于就是在右侧
  target = targetR;
 }else if(CGRectGetMaxX(self.mainV.frame) < screenW * 0.5){
  //2.判断在左侧
  //当前View的最大的x有没有小于屏幕宽度的一半,小于就是在左侧
  target = targetL;
 }


 //计算当前mainV的frame.
 CGFloat offset = target - self.mainV.frame.origin.x;
 [UIView animateWithDuration:0.5 animations:^{

  self.mainV.frame = [self frameWithOffsetX:offset];
 }];


 }


 //复位
 [pan setTranslation:CGPointZero inView:self.mainV];

}

#define maxY 100
//根据偏移量计算MainV的frame
- (CGRect)frameWithOffsetX:(CGFloat)offsetX {

 NSLog(@"offsetX===%f",offsetX);

 CGRect frame = self.mainV.frame;
 NSLog(@"x====%f",frame.origin.x);
 frame.origin.x += offsetX;

 //当拖动的View的x值等于屏幕宽度时,maxY为最大,最大为100
 // 375 * 100 / 375 = 100

 //对计算的结果取绝对值
 CGFloat y = fabs( frame.origin.x * maxY / screenW);
 frame.origin.y = y;


 //屏幕的高度减去两倍的Y值
 frame.size.height = [UIScreen mainScreen].bounds.size.height - (2 * frame.origin.y);

 return frame;
}


- (void)setUp{

 //leftV
 UIView *leftV = [[UIView alloc] initWithFrame:self.view.bounds];
 leftV.backgroundColor = [UIColor blueColor];
 self.leftV = leftV;
 [self.view addSubview:leftV];
 //rightV
 UIView *rightV = [[UIView alloc] initWithFrame:self.view.bounds];
 rightV.backgroundColor = [UIColor greenColor];
 self.rightV = rightV;
 [self.view addSubview:rightV];
 //mianV
 UIView *mainV = [[UIView alloc] initWithFrame:self.view.bounds];
 mainV.backgroundColor = [UIColor redColor];
 self.mainV = mainV;
 [self.view addSubview:mainV];
}

@end