实现简易抽屉效果和双边抽屉的效果

@interface ViewController () {
 UIView* _leftView;
}
 
@end
 
@implementation ViewController
 
- (void)viewDidLoad {
 [super viewDidLoad];
 // Do any additional setup after loading the view, typically from a nib.
  
 _leftView = [[UIView alloc] init];
 //把左侧边的view先隐藏
 _leftView.frame = CGRectMake(-200, 0, 200, self.view.frame.size.height);
 _leftView.backgroundColor = [UIColor greenColor];
 [self.view addSubview:_leftView];
  
 UIPanGestureRecognizer* pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
 [self.view addGestureRecognizer:pan];
}
 
- (void)handlePan:(UIPanGestureRecognizer*) recognizer {
 CGPoint translation = [recognizer translationInView:self.view];
 //增量后的x坐标位置
 CGFloat Xresult = translation.x + _leftView.frame.origin.x;
  
 //向右
 if (translation.x >= 0) {
  //leftView已全部拉出，则无法再向右
  if (_leftView.frame.origin.x >= 0 || Xresult >= 0) {
   _leftView.frame = CGRectMake(0, 0, 200, self.view.frame.size.height);
    
   return;
  }
 } else if (translation.x < 0) {//向左
  //leftView已全部收回，则无法再向左
  if (_leftView.frame.origin.x <= -200 || Xresult <= -200) {
   _leftView.frame = CGRectMake(-200, 0, 200, self.view.frame.size.height);
   return;
  }
 }
  
 CGRect frame = _leftView.frame;
 frame.origin.x += translation.x;
 _leftView.frame = frame;
  
 //清空移动的距离，这是关键
 [recognizer setTranslation:CGPointZero inView:recognizer.view];
  
 //做弹回效果，以中轴为界限
 if (recognizer.state == UIGestureRecognizerStateEnded) {
  if (_leftView.frame.origin.x > -100) {
   [self closeView:NO];
  } else {
   [self closeView:YES];
  }
 }
}
 
- (void)closeView:(BOOL)close {
 if (close) {
  [self moveView:CGRectMake(-200, 0, 200, self.view.frame.size.height)];
 } else {
  [self moveView:CGRectMake(0, 0, 200, self.view.frame.size.height)];
 }
}
 
- (void)moveView:(CGRect)frame {
 [UIView animateWithDuration:0.3 animations:^{
  _leftView.frame = frame;
 } completion:^(BOOL finished) {
   
 }];
}

#import "PathView.h"
#import "UIView+Additions.h"
 
@implementation PathView
 
- (instancetype)init {
 self = [super init];
 if (self) {
  [self setupGestureRecognizer];
 }
 return self;
}
 
- (void)setupGestureRecognizer {
 UIPanGestureRecognizer* pan = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(handlePan:)];
 [self addGestureRecognizer:pan];
}
 
- (void)handlePan:(UIPanGestureRecognizer*)recognizer {
 CGPoint translation = [recognizer translationInView:self];
  
 CGFloat Xresult = translation.x + self.left;
  
 if (translation.x >= 0) {//向右
  if (self.left >= _leftWidth || Xresult >= _leftWidth) {
   self.frame = CGRectMake(_leftWidth, 0, self.width, self.height);
   return;
  }
 }
 else if (translation.x < 0) {//向左
  if (self.left <= -_rightWidth || Xresult <= -_rightWidth) {
   self.frame = CGRectMake(-_rightWidth, 0, self.width, self.height);
   return;
  }
 }
  
 self.left += translation.x;
  
 if (recognizer.state == UIGestureRecognizerStateEnded) {
  if (self.left > _leftWidth / 2) {
   [self openLeft:YES openRight:NO];
  }
   
  else if (self.left < -(_rightWidth / 2)) {
   [self openLeft:NO openRight:YES];
  }
   
  else {
   [self openLeft:NO openRight:NO];
  }
 }
  
 //清空移动的距离
 [recognizer setTranslation:CGPointZero inView:recognizer.view];
}
 
- (void)openLeft:(BOOL)left openRight:(BOOL)right {
 if (!left && !right) {
  [self moveView:CGRectMake(0, 0, self.width, self.height)];
   
 } else if (!left && right) {
  [self moveView:CGRectMake(-_rightWidth, 0, self.width, self.height)];
   
 } else if (left && !right) {
  [self moveView:CGRectMake(_leftWidth, 0, self.width, self.height)];
   
 }
}
 
- (void)moveView:(CGRect)frame {
 [UIView animateWithDuration:0.3 animations:^{
  self.frame = frame;
 } completion:^(BOOL finished) {
   
 }];
}