@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];
 //把左側(cè)邊的view先隱藏
 _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坐標(biāo)位置
 CGFloat Xresult = translation.x + _leftView.frame.origin.x;
 
 //向右
 if (translation.x >= 0) {
 //leftView已全部拉出，則無法再向右
 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，則無法再向左
 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;
 
 //清空移動的距離，這是關(guān)鍵
 [recognizer setTranslation:CGPointZero inView:recognizer.view];
 
 //做彈回效果，以中軸為界限
 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];
 }
 }
 
 //清空移動的距離
 [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) {
  
 }];
}